From 3d9a108bdcf3251124617693dfc8dd6f477d4139 Mon Sep 17 00:00:00 2001
From: Janis <janis-e@gmx.de>
Date: Sat, 4 Apr 2026 17:11:11 +0200
Subject: [PATCH] refactor(core): NCS-22 update GameEngine to use GameContext
 and integrate Rule module

---
 compile                                       |   0
 coverage                                      |   0
 .../de/nowchess/chess/command/Command.scala   |  19 +-
 .../de/nowchess/chess/engine/GameEngine.scala | 383 ++++++-------
 .../nowchess/chess/notation/PgnParser.scala   | 211 +++----
 .../command/CommandInvokerBranchTest.scala    |  78 +--
 .../chess/command/CommandInvokerTest.scala    |  17 +-
 .../CommandInvokerThreadSafetyTest.scala      |  29 +-
 .../nowchess/chess/command/CommandTest.scala  |  18 +-
 .../command/MoveCommandDefaultsTest.scala     |  54 ++
 .../command/MoveCommandImmutabilityTest.scala |  36 +-
 .../chess/controller/GameControllerTest.scala | 526 ------------------
 .../engine/GameEngineEdgeCasesTest.scala      |   2 -
 .../engine/GameEngineGameEndingTest.scala     |  12 +-
 .../GameEngineHandleFailedMoveTest.scala      |   1 -
 .../engine/GameEngineInvalidMovesTest.scala   |   1 -
 .../chess/engine/GameEngineLoadPgnTest.scala  |  32 +-
 .../engine/GameEnginePromotionTest.scala      |  51 +-
 .../chess/engine/GameEngineTest.scala         |  47 +-
 .../engine/MoveCommandDefaultsTest.scala      | 110 ----
 .../logic/CastlingRightsCalculatorTest.scala  |  70 ---
 .../chess/logic/EnPassantCalculatorTest.scala | 101 ----
 .../chess/logic/GameHistoryTest.scala         |   9 +-
 .../nowchess/chess/logic/GameRulesTest.scala  | 161 ------
 .../chess/logic/MoveValidatorTest.scala       | 280 ----------
 .../chess/notation/FenExporterTest.scala      |   5 +-
 .../chess/notation/PgnExporterTest.scala      |   6 +-
 .../chess/notation/PgnParserTest.scala        | 112 ++--
 .../chess/notation/PgnValidatorTest.scala     |   6 +-
 .../observer/ObservableThreadSafetyTest.scala |   8 +-
 .../scala/de/nowchess/rules/RuleSet.scala     |   6 +
 .../de/nowchess/rules/StandardRules.scala     |  91 ++-
 modules/ui/build.gradle.kts                   |   1 +
 .../de/nowchess/ui/gui/ChessBoardView.scala   |   1 -
 .../test/scala/de/nowchess/ui/MainTest.scala  |  22 -
 .../nowchess/ui/terminal/TerminalUITest.scala | 327 -----------
 36 files changed, 527 insertions(+), 2306 deletions(-)
 mode change 100644 => 100755 compile
 mode change 100644 => 100755 coverage
 create mode 100644 modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandDefaultsTest.scala
 delete mode 100644 modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala
 delete mode 100644 modules/core/src/test/scala/de/nowchess/chess/engine/MoveCommandDefaultsTest.scala
 delete mode 100644 modules/core/src/test/scala/de/nowchess/chess/logic/CastlingRightsCalculatorTest.scala
 delete mode 100644 modules/core/src/test/scala/de/nowchess/chess/logic/EnPassantCalculatorTest.scala
 delete mode 100644 modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala
 delete mode 100644 modules/core/src/test/scala/de/nowchess/chess/logic/MoveValidatorTest.scala
 delete mode 100644 modules/ui/src/test/scala/de/nowchess/ui/MainTest.scala
 delete mode 100644 modules/ui/src/test/scala/de/nowchess/ui/terminal/TerminalUITest.scala

diff --git a/compile b/compile
old mode 100644
new mode 100755
diff --git a/coverage b/coverage
old mode 100644
new mode 100755
diff --git a/modules/core/src/main/scala/de/nowchess/chess/command/Command.scala b/modules/core/src/main/scala/de/nowchess/chess/command/Command.scala
index 582da08..a9aaf94 100644
--- a/modules/core/src/main/scala/de/nowchess/chess/command/Command.scala
+++ b/modules/core/src/main/scala/de/nowchess/chess/command/Command.scala
@@ -1,7 +1,7 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, Board, Color, Piece}
-import de.nowchess.api.game.GameHistory
+import de.nowchess.api.board.{Square, Piece}
+import de.nowchess.api.game.GameContext
 
 /** Marker trait for all commands that can be executed and undone.
  *  Commands encapsulate user actions and game state transitions.
@@ -23,23 +23,22 @@ case class MoveCommand(
   from: Square,
   to: Square,
   moveResult: Option[MoveResult] = None,
-  previousBoard: Option[Board] = None,
-  previousHistory: Option[GameHistory] = None,
-  previousTurn: Option[Color] = None
+  previousContext: Option[GameContext] = None,
+  notation: String = ""
 ) extends Command:
 
   override def execute(): Boolean =
     moveResult.isDefined
 
   override def undo(): Boolean =
-    previousBoard.isDefined && previousHistory.isDefined && previousTurn.isDefined
+    previousContext.isDefined
 
   override def description: String = s"Move from $from to $to"
 
 // Sealed hierarchy of move outcomes (for tracking state changes)
 sealed trait MoveResult
 object MoveResult:
-  case class Successful(newBoard: Board, newHistory: GameHistory, newTurn: Color, captured: Option[Piece]) extends MoveResult
+  case class Successful(newContext: GameContext, captured: Option[Piece]) extends MoveResult
   case object InvalidFormat extends MoveResult
   case object InvalidMove extends MoveResult
 
@@ -51,14 +50,12 @@ case class QuitCommand() extends Command:
 
 /** Command to reset the board to initial position. */
 case class ResetCommand(
-  previousBoard: Option[Board] = None,
-  previousHistory: Option[GameHistory] = None,
-  previousTurn: Option[Color] = None
+  previousContext: Option[GameContext] = None
 ) extends Command:
 
   override def execute(): Boolean = true
 
   override def undo(): Boolean =
-    previousBoard.isDefined && previousHistory.isDefined && previousTurn.isDefined
+    previousContext.isDefined
 
   override def description: String = "Reset board"
diff --git a/modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala b/modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala
index d1753c0..3ce8657 100644
--- a/modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala
+++ b/modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala
@@ -1,57 +1,36 @@
 package de.nowchess.chess.engine
 
-import de.nowchess.api.board.{Board, Color, Piece, Square, CastlingRights}
-import de.nowchess.api.move.{PromotionPiece, Move}
-import de.nowchess.api.game.{GameHistory, GameContext}
-import de.nowchess.chess.controller.{GameController, Parser, MoveResult}
+import de.nowchess.api.board.{Board, Color, Piece, PieceType, Square}
+import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
+import de.nowchess.api.game.GameContext
+import de.nowchess.chess.controller.Parser
 import de.nowchess.chess.observer.*
-import de.nowchess.chess.command.{CommandInvoker, MoveCommand}
+import de.nowchess.chess.command.{CommandInvoker, MoveCommand, MoveResult}
 import de.nowchess.chess.notation.{PgnExporter, PgnParser}
+import de.nowchess.rules.{RuleSet, StandardRules}
 
 /** Pure game engine that manages game state and notifies observers of state changes.
- *  This class is the single source of truth for the game state.
- *  All user interactions must go through this engine via Commands, and all state changes
- *  are communicated to observers via GameEvent notifications.
+ *  All rule queries delegate to the injected RuleSet.
+ *  All user interactions go through Commands; state changes are broadcast via GameEvents.
  */
 class GameEngine(
-  initialBoard: Board = Board.initial,
-  initialHistory: GameHistory = GameHistory.empty,
-  initialTurn: Color = Color.White,
-  completePromotionFn: (Board, GameHistory, Square, Square, PromotionPiece, Color) => MoveResult =
-    GameController.completePromotion
+  initialContext: GameContext = GameContext.initial,
+  ruleSet: RuleSet = StandardRules
 ) extends Observable:
-  private var currentBoard: Board = initialBoard
-  private var currentHistory: GameHistory = initialHistory
-  private var currentTurn: Color = initialTurn
+  private var currentContext: GameContext = initialContext
   private val invoker = new CommandInvoker()
 
-  /** Inner class for tracking pending promotion state */
-  private case class PendingPromotion(
-    from: Square, to: Square,
-    boardBefore: Board, historyBefore: GameHistory,
-    turn: Color
-  )
-
-  /** Current pending promotion, if any */
+  /** Pending promotion: the Move that triggered it (from/to only, moveType filled in later). */
+  private case class PendingPromotion(from: Square, to: Square, contextBefore: GameContext)
   private var pendingPromotion: Option[PendingPromotion] = None
 
   /** True if a pawn promotion move is pending and needs a piece choice. */
   def isPendingPromotion: Boolean = synchronized { pendingPromotion.isDefined }
 
   // Synchronized accessors for current state
-  def board: Board = synchronized { currentBoard }
-  def history: GameHistory = synchronized { currentHistory }
-  def turn: Color = synchronized { currentTurn }
-
-  /** Create a GameContext from current state (for event creation). */
-  private def currentContext: GameContext = GameContext(
-    board = currentBoard,
-    turn = currentTurn,
-    castlingRights = CastlingRights.Initial, // TODO: derive from history
-    enPassantSquare = None,                  // TODO: derive from history
-    halfMoveClock = currentHistory.halfMoveClock,
-    moves = List.empty                        // TODO: convert history moves to api.move.Move
-  )
+  def board: Board   = synchronized { currentContext.board }
+  def turn: Color    = synchronized { currentContext.turn }
+  def context: GameContext = synchronized { currentContext }
 
   /** Check if undo is available. */
   def canUndo: Boolean = synchronized { invoker.canUndo }
@@ -69,7 +48,6 @@ class GameEngine(
     val trimmed = rawInput.trim.toLowerCase
     trimmed match
       case "quit" | "q" =>
-        // Client should handle quit logic; we just return
         ()
 
       case "undo" =>
@@ -79,10 +57,8 @@ class GameEngine(
         performRedo()
 
       case "draw" =>
-        if currentHistory.halfMoveClock >= 100 then
-          currentBoard   = Board.initial
-          currentHistory = GameHistory.empty
-          currentTurn    = Color.White
+        if currentContext.halfMoveClock >= 100 then
+          currentContext = GameContext.initial
           invoker.clear()
           notifyObservers(DrawClaimedEvent(currentContext))
         else
@@ -92,11 +68,7 @@ class GameEngine(
           ))
 
       case "" =>
-        val event = InvalidMoveEvent(
-          currentContext,
-          "Please enter a valid move or command."
-        )
-        notifyObservers(event)
+        notifyObservers(InvalidMoveEvent(currentContext, "Please enter a valid move or command."))
 
       case moveInput =>
         Parser.parseMove(moveInput) match
@@ -106,67 +78,35 @@ class GameEngine(
               s"Invalid move format '$moveInput'. Use coordinate notation, e.g. e2e4."
             ))
           case Some((from, to)) =>
-            handleParsedMove(from, to, moveInput)
+            handleParsedMove(from, to)
   }
 
-  private def handleParsedMove(from: Square, to: Square, moveInput: String): Unit =
-    val cmd = MoveCommand(
-      from = from,
-      to = to,
-      previousBoard = Some(currentBoard),
-      previousHistory = Some(currentHistory),
-      previousTurn = Some(currentTurn)
-    )
-    GameController.processMove(currentBoard, currentHistory, currentTurn, moveInput) match
-      case MoveResult.InvalidFormat(_) | MoveResult.NoPiece | MoveResult.WrongColor | MoveResult.IllegalMove | MoveResult.Quit =>
-        handleFailedMove(moveInput)
+  private def handleParsedMove(from: Square, to: Square): Unit =
+    currentContext.board.pieceAt(from) match
+      case None =>
+        notifyObservers(InvalidMoveEvent(currentContext, "No piece on that square."))
+      case Some(piece) if piece.color != currentContext.turn =>
+        notifyObservers(InvalidMoveEvent(currentContext, "That is not your piece."))
+      case Some(piece) =>
+        val legal = ruleSet.legalMoves(currentContext, from)
+        // Find all legal moves going to `to`
+        val candidates = legal.filter(_.to == to)
+        candidates match
+          case Nil =>
+            notifyObservers(InvalidMoveEvent(currentContext, "Illegal move."))
+          case moves if isPromotionMove(piece, to) =>
+            // Multiple moves (one per promotion piece) — ask user to choose
+            val contextBefore = currentContext
+            pendingPromotion = Some(PendingPromotion(from, to, contextBefore))
+            notifyObservers(PromotionRequiredEvent(currentContext, from, to))
+          case move :: _ =>
+            executeMove(move)
 
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-        invoker.execute(updatedCmd)
-        updateGameState(newBoard, newHistory, newTurn)
-        emitMoveEvent(from.toString, to.toString, captured, newTurn)
-        if currentHistory.halfMoveClock >= 100 then
-          notifyObservers(FiftyMoveRuleAvailableEvent(currentContext))
-
-      case MoveResult.MovedInCheck(newBoard, newHistory, captured, newTurn) =>
-        val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-        invoker.execute(updatedCmd)
-        updateGameState(newBoard, newHistory, newTurn)
-        emitMoveEvent(from.toString, to.toString, captured, newTurn)
-        notifyObservers(CheckDetectedEvent(currentContext))
-        if currentHistory.halfMoveClock >= 100 then
-          notifyObservers(FiftyMoveRuleAvailableEvent(currentContext))
-
-      case MoveResult.Checkmate(winner) =>
-        val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-        invoker.execute(updatedCmd)
-        currentBoard = Board.initial
-        currentHistory = GameHistory.empty
-        currentTurn = Color.White
-        notifyObservers(CheckmateEvent(currentContext, winner))
-
-      case MoveResult.Stalemate =>
-        val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-        invoker.execute(updatedCmd)
-        currentBoard = Board.initial
-        currentHistory = GameHistory.empty
-        currentTurn = Color.White
-        notifyObservers(StalemateEvent(currentContext))
-
-      case MoveResult.PromotionRequired(promFrom, promTo, boardBefore, histBefore, _, promotingTurn) =>
-        pendingPromotion = Some(PendingPromotion(promFrom, promTo, boardBefore, histBefore, promotingTurn))
-        notifyObservers(PromotionRequiredEvent(currentContext, promFrom, promTo))
-
-  /** Undo the last move. */
-  def undo(): Unit = synchronized {
-    performUndo()
-  }
-
-  /** Redo the last undone move. */
-  def redo(): Unit = synchronized {
-    performRedo()
-  }
+  private def isPromotionMove(piece: Piece, to: Square): Boolean =
+    piece.pieceType == PieceType.Pawn && {
+      val promoRank = if piece.color == Color.White then 7 else 0
+      to.rank.ordinal == promoRank
+    }
 
   /** Apply a player's promotion piece choice.
    *  Must only be called when isPendingPromotion is true.
@@ -177,88 +117,48 @@ class GameEngine(
         notifyObservers(InvalidMoveEvent(currentContext, "No promotion pending."))
       case Some(pending) =>
         pendingPromotion = None
-        val cmd = MoveCommand(
-          from = pending.from,
-          to = pending.to,
-          previousBoard = Some(pending.boardBefore),
-          previousHistory = Some(pending.historyBefore),
-          previousTurn = Some(pending.turn)
-        )
-        completePromotionFn(
-          pending.boardBefore, pending.historyBefore,
-          pending.from, pending.to, piece, pending.turn
-        ) match
-          case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-            invoker.execute(updatedCmd)
-            updateGameState(newBoard, newHistory, newTurn)
-            emitMoveEvent(pending.from.toString, pending.to.toString, captured, newTurn)
-
-          case MoveResult.MovedInCheck(newBoard, newHistory, captured, newTurn) =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-            invoker.execute(updatedCmd)
-            updateGameState(newBoard, newHistory, newTurn)
-            emitMoveEvent(pending.from.toString, pending.to.toString, captured, newTurn)
-            notifyObservers(CheckDetectedEvent(currentContext))
-
-          case MoveResult.Checkmate(winner) =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-            invoker.execute(updatedCmd)
-            currentBoard = Board.initial
-            currentHistory = GameHistory.empty
-            currentTurn = Color.White
-            notifyObservers(CheckmateEvent(currentContext, winner))
-
-          case MoveResult.Stalemate =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-            invoker.execute(updatedCmd)
-            currentBoard = Board.initial
-            currentHistory = GameHistory.empty
-            currentTurn = Color.White
-            notifyObservers(StalemateEvent(currentContext))
-
-          case _ =>
-            notifyObservers(InvalidMoveEvent(currentContext, "Error completing promotion."))
+        val move = Move(pending.from, pending.to, MoveType.Promotion(piece))
+        // Verify it's actually legal
+        val legal = ruleSet.legalMoves(currentContext, pending.from)
+        if legal.contains(move) then
+          executeMove(move)
+        else
+          notifyObservers(InvalidMoveEvent(currentContext, "Error completing promotion."))
   }
 
+  /** Undo the last move. */
+  def undo(): Unit = synchronized { performUndo() }
+
+  /** Redo the last undone move. */
+  def redo(): Unit = synchronized { performRedo() }
+
   /** Validate and load a PGN string.
    *  Each move is replayed through the command system so undo/redo is available after loading.
-   *  Returns Right(()) on success; Left(error) if any move is illegal or the position impossible. */
+   */
   def loadPgn(pgn: String): Either[String, Unit] = synchronized {
     PgnParser.validatePgn(pgn) match
-      case Left(err) =>
-        Left(err)
+      case Left(err) => Left(err)
       case Right(game) =>
-        val initialBoardBeforeLoad = currentBoard
-        val initialHistoryBeforeLoad = currentHistory
-        val initialTurnBeforeLoad = currentTurn
-        
-        currentBoard = Board.initial
-        currentHistory = GameHistory.empty
-        currentTurn = Color.White
+        val savedContext = currentContext
+        currentContext = GameContext.initial
         pendingPromotion = None
         invoker.clear()
 
         var error: Option[String] = None
         import scala.util.control.Breaks._
         breakable {
-          game.moves.foreach { move =>
-            handleParsedMove(move.from, move.to, s"${move.from}${move.to}")
-            move.promotionPiece.foreach(completePromotion)
-            
-            // If the move failed to execute properly, stop and report
-            // (validatePgn should have caught this, but we're being safe)
-            if pendingPromotion.isDefined && move.promotionPiece.isEmpty then
-              error = Some(s"Promotion required for move ${move.from}${move.to}")
+          game.moves.foreach { histMove =>
+            handleParsedMove(histMove.from, histMove.to)
+            histMove.promotionPiece.foreach(completePromotion)
+            if pendingPromotion.isDefined && histMove.promotionPiece.isEmpty then
+              error = Some(s"Promotion required for move ${histMove.from}${histMove.to}")
               break()
           }
         }
-        
+
         error match
           case Some(err) =>
-            currentBoard = initialBoardBeforeLoad
-            currentHistory = initialHistoryBeforeLoad
-            currentTurn = initialTurnBeforeLoad
+            currentContext = savedContext
             Left(err)
           case None =>
             notifyObservers(PgnLoadedEvent(currentContext))
@@ -266,10 +166,8 @@ class GameEngine(
   }
 
   /** Load an arbitrary board position, clearing all history and undo/redo state. */
-  def loadPosition(board: Board, history: GameHistory, turn: Color): Unit = synchronized {
-    currentBoard = board
-    currentHistory = history
-    currentTurn = turn
+  def loadPosition(newContext: GameContext): Unit = synchronized {
+    currentContext = newContext
     pendingPromotion = None
     invoker.clear()
     notifyObservers(BoardResetEvent(currentContext))
@@ -277,28 +175,97 @@ class GameEngine(
 
   /** Reset the board to initial position. */
   def reset(): Unit = synchronized {
-    currentBoard = Board.initial
-    currentHistory = GameHistory.empty
-    currentTurn = Color.White
+    currentContext = GameContext.initial
     invoker.clear()
-    notifyObservers(BoardResetEvent(
-      currentContext
-    ))
+    notifyObservers(BoardResetEvent(currentContext))
   }
 
-  // ──── Private Helpers ────
+  // ──── Private helpers ────
+
+  private def executeMove(move: Move): Unit =
+    val contextBefore = currentContext
+    val nextContext = ruleSet.applyMove(currentContext, move)
+    val captured = computeCaptured(currentContext, move)
+
+    val cmd = MoveCommand(
+      from = move.from,
+      to = move.to,
+      moveResult = Some(MoveResult.Successful(nextContext, captured)),
+      previousContext = Some(contextBefore),
+      notation = moveToPgn(move, contextBefore.board)
+    )
+    invoker.execute(cmd)
+    currentContext = nextContext
+
+    notifyObservers(MoveExecutedEvent(
+      currentContext,
+      move.from.toString,
+      move.to.toString,
+      captured.map(c => s"${c.color.label} ${c.pieceType.label}")
+    ))
+
+    if ruleSet.isCheckmate(currentContext) then
+      val winner = currentContext.turn.opposite
+      currentContext = GameContext.initial
+      notifyObservers(CheckmateEvent(currentContext, winner))
+    else if ruleSet.isStalemate(currentContext) then
+      currentContext = GameContext.initial
+      notifyObservers(StalemateEvent(currentContext))
+    else if ruleSet.isCheck(currentContext) then
+      notifyObservers(CheckDetectedEvent(currentContext))
+
+    if currentContext.halfMoveClock >= 100 then
+      notifyObservers(FiftyMoveRuleAvailableEvent(currentContext))
+
+  private def moveToPgn(move: Move, boardBefore: Board): String =
+    move.moveType match
+      case MoveType.CastleKingside  => "O-O"
+      case MoveType.CastleQueenside => "O-O-O"
+      case MoveType.EnPassant =>
+        s"${move.from.file.toString.toLowerCase}x${move.to}"
+      case MoveType.Promotion(pp) =>
+        val ppChar = pp match
+          case PromotionPiece.Queen  => "Q"
+          case PromotionPiece.Rook   => "R"
+          case PromotionPiece.Bishop => "B"
+          case PromotionPiece.Knight => "N"
+        s"${move.to}=$ppChar"
+      case MoveType.Normal =>
+        val isCapture = boardBefore.pieceAt(move.to).isDefined
+        boardBefore.pieceAt(move.from).map(_.pieceType) match
+          case Some(PieceType.Pawn) =>
+            if isCapture then s"${move.from.file.toString.toLowerCase}x${move.to}"
+            else move.to.toString
+          case Some(pt) =>
+            val letter = pt match
+              case PieceType.Knight => "N"
+              case PieceType.Bishop => "B"
+              case PieceType.Rook   => "R"
+              case PieceType.Queen  => "Q"
+              case PieceType.King   => "K"
+              case _                => ""
+            if isCapture then s"${letter}x${move.to}" else s"$letter${move.to}"
+          case None => move.to.toString
+
+  private def computeCaptured(context: GameContext, move: Move): Option[Piece] =
+    move.moveType match
+      case MoveType.EnPassant =>
+        // Captured pawn is on the same rank as the moving pawn, same file as destination
+        val capturedSquare = Square(move.to.file, move.from.rank)
+        context.board.pieceAt(capturedSquare)
+      case MoveType.CastleKingside | MoveType.CastleQueenside =>
+        None
+      case _ =>
+        context.board.pieceAt(move.to)
 
   private def performUndo(): Unit =
     if invoker.canUndo then
       val cmd = invoker.history(invoker.getCurrentIndex)
       (cmd: @unchecked) match
         case moveCmd: MoveCommand =>
-          val notation = currentHistory.moves.lastOption.map(PgnExporter.moveToAlgebraic).getOrElse("")
-          moveCmd.previousBoard.foreach(currentBoard = _)
-          moveCmd.previousHistory.foreach(currentHistory = _)
-          moveCmd.previousTurn.foreach(currentTurn = _)
+          moveCmd.previousContext.foreach(currentContext = _)
           invoker.undo()
-          notifyObservers(MoveUndoneEvent(currentContext, notation))
+          notifyObservers(MoveUndoneEvent(currentContext, moveCmd.notation))
     else
       notifyObservers(InvalidMoveEvent(currentContext, "Nothing to undo."))
 
@@ -307,44 +274,16 @@ class GameEngine(
       val cmd = invoker.history(invoker.getCurrentIndex + 1)
       (cmd: @unchecked) match
         case moveCmd: MoveCommand =>
-          for case de.nowchess.chess.command.MoveResult.Successful(nb, nh, nt, cap) <- moveCmd.moveResult do
-            updateGameState(nb, nh, nt)
+          for case MoveResult.Successful(nextCtx, cap) <- moveCmd.moveResult do
+            currentContext = nextCtx
             invoker.redo()
-            val notation    = nh.moves.lastOption.map(PgnExporter.moveToAlgebraic).getOrElse("")
             val capturedDesc = cap.map(c => s"${c.color.label} ${c.pieceType.label}")
-            notifyObservers(MoveRedoneEvent(currentContext, notation, moveCmd.from.toString, moveCmd.to.toString, capturedDesc))
+            notifyObservers(MoveRedoneEvent(
+              currentContext,
+              moveCmd.notation,
+              moveCmd.from.toString,
+              moveCmd.to.toString,
+              capturedDesc
+            ))
     else
       notifyObservers(InvalidMoveEvent(currentContext, "Nothing to redo."))
-
-  private def updateGameState(newBoard: Board, newHistory: GameHistory, newTurn: Color): Unit =
-    currentBoard = newBoard
-    currentHistory = newHistory
-    currentTurn = newTurn
-
-  private def emitMoveEvent(fromSq: String, toSq: String, captured: Option[Piece], newTurn: Color): Unit =
-    val capturedDesc = captured.map(c => s"${c.color.label} ${c.pieceType.label}")
-    notifyObservers(MoveExecutedEvent(
-      currentContext,
-      fromSq,
-      toSq,
-      capturedDesc
-    ))
-
-  private def handleFailedMove(moveInput: String): Unit =
-    (GameController.processMove(currentBoard, currentHistory, currentTurn, moveInput): @unchecked) match
-      case MoveResult.NoPiece =>
-        notifyObservers(InvalidMoveEvent(
-          currentContext,
-          "No piece on that square."
-        ))
-      case MoveResult.WrongColor =>
-        notifyObservers(InvalidMoveEvent(
-          currentContext,
-          "That is not your piece."
-        ))
-      case MoveResult.IllegalMove =>
-        notifyObservers(InvalidMoveEvent(
-          currentContext,
-          "Illegal move."
-        ))
-
diff --git a/modules/core/src/main/scala/de/nowchess/chess/notation/PgnParser.scala b/modules/core/src/main/scala/de/nowchess/chess/notation/PgnParser.scala
index 2ee0304..a22c29e 100644
--- a/modules/core/src/main/scala/de/nowchess/chess/notation/PgnParser.scala
+++ b/modules/core/src/main/scala/de/nowchess/chess/notation/PgnParser.scala
@@ -1,8 +1,9 @@
 package de.nowchess.chess.notation
 
 import de.nowchess.api.board.*
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.api.game.{GameHistory, HistoryMove}
+import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
+import de.nowchess.api.game.{GameContext, HistoryMove}
+import de.nowchess.rules.StandardRules
 
 /** A parsed PGN game containing headers and the resolved move list. */
 case class PgnGame(
@@ -27,11 +28,9 @@ object PgnParser:
   def parsePgn(pgn: String): Option[PgnGame] =
     val lines = pgn.split("\n").map(_.trim)
     val (headerLines, rest) = lines.span(_.startsWith("["))
-
     val headers  = parseHeaders(headerLines)
     val moveText = rest.mkString(" ")
     val moves    = parseMovesText(moveText)
-
     Some(PgnGame(headers, moves))
 
   /** Parse PGN header lines of the form [Key "Value"]. */
@@ -42,40 +41,32 @@ object PgnParser:
   /** Parse the move-text section (e.g. "1. e4 e5 2. Nf3") into resolved HistoryMoves. */
   private def parseMovesText(moveText: String): List[HistoryMove] =
     val tokens = moveText.split("\\s+").filter(_.nonEmpty)
-
-    // Fold over tokens, threading (board, history, currentColor, accumulator)
-    val (_, _, _, moves) = tokens.foldLeft(
-      (Board.initial, GameHistory.empty, Color.White, List.empty[HistoryMove])
+    val (_, _, moves) = tokens.foldLeft(
+      (GameContext.initial, Color.White, List.empty[HistoryMove])
     ):
-      case (state @ (board, history, color, acc), token) =>
-        // Skip move-number markers (e.g. "1.", "2.") and result tokens
+      case (state @ (ctx, color, acc), token) =>
         if isMoveNumberOrResult(token) then state
         else
-          parseAlgebraicMove(token, board, history, color) match
-            case None       => state  // unrecognised token — skip silently
+          parseAlgebraicMove(token, ctx, color) match
+            case None       => state
             case Some(move) =>
-              val newBoard   = applyMoveToBoard(board, move, color)
-              val newHistory = history.addMove(move)
-              (newBoard, newHistory, color.opposite, acc :+ move)
-
+              val histMove   = toHistoryMove(move, ctx, color)
+              val nextCtx    = StandardRules.applyMove(ctx, move)
+              (nextCtx, color.opposite, acc :+ histMove)
     moves
 
-  /** Apply a single HistoryMove to a Board, handling castling and promotion. */
-  private def applyMoveToBoard(board: Board, move: HistoryMove, color: Color): Board =
-    move.castleSide match
-      case Some("Kingside") => board.withCastle(color, CastleSide.Kingside)
-      case Some("Queenside") => board.withCastle(color, CastleSide.Queenside)
-      case _ =>
-        val (boardAfterMove, _) = board.withMove(move.from, move.to)
-        move.promotionPiece match
-          case Some(pp) =>
-            val pieceType = pp match
-              case PromotionPiece.Queen  => PieceType.Queen
-              case PromotionPiece.Rook   => PieceType.Rook
-              case PromotionPiece.Bishop => PieceType.Bishop
-              case PromotionPiece.Knight => PieceType.Knight
-            boardAfterMove.updated(move.to, Piece(color, pieceType))
-          case None => boardAfterMove
+  /** Convert an api.move.Move to a HistoryMove given the board context before the move. */
+  private def toHistoryMove(move: Move, ctx: GameContext, color: Color): HistoryMove =
+    val castleSide = move.moveType match
+      case MoveType.CastleKingside  => Some("Kingside")
+      case MoveType.CastleQueenside => Some("Queenside")
+      case _                        => None
+    val promotionPiece = move.moveType match
+      case MoveType.Promotion(pp) => Some(pp)
+      case _                      => None
+    val pieceType = ctx.board.pieceAt(move.from).map(_.pieceType).getOrElse(PieceType.Pawn)
+    val isCapture = ctx.board.pieceAt(move.to).isDefined || move.moveType == MoveType.EnPassant
+    HistoryMove(move.from, move.to, castleSide, promotionPiece, pieceType, isCapture)
 
   /** True for move-number tokens ("1.", "12.") and PGN result tokens. */
   private def isMoveNumberOrResult(token: String): Boolean =
@@ -85,85 +76,74 @@ object PgnParser:
     token == "0-1"             ||
     token == "1/2-1/2"
 
-  /** Parse a single algebraic notation token into a HistoryMove, given the current board state. */
-  def parseAlgebraicMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
+  /** Parse a single algebraic notation token into a Move, given the current game context. */
+  def parseAlgebraicMove(notation: String, ctx: GameContext, color: Color): Option[Move] =
     notation match
       case "O-O" | "O-O+" | "O-O#" =>
         val rank = if color == Color.White then Rank.R1 else Rank.R8
-        Some(HistoryMove(Square(File.E, rank), Square(File.G, rank), Some("Kingside"), pieceType = PieceType.King))
+        val move = Move(Square(File.E, rank), Square(File.G, rank), MoveType.CastleKingside)
+        Option.when(StandardRules.legalMoves(ctx, Square(File.E, rank)).contains(move))(move)
 
       case "O-O-O" | "O-O-O+" | "O-O-O#" =>
         val rank = if color == Color.White then Rank.R1 else Rank.R8
-        Some(HistoryMove(Square(File.E, rank), Square(File.C, rank), Some("Queenside"), pieceType = PieceType.King))
+        val move = Move(Square(File.E, rank), Square(File.C, rank), MoveType.CastleQueenside)
+        Option.when(StandardRules.legalMoves(ctx, Square(File.E, rank)).contains(move))(move)
 
       case _ =>
-        parseRegularMove(notation, board, history, color)
+        parseRegularMove(notation, ctx, color)
 
   /** Parse regular algebraic notation (pawn moves, piece moves, captures, disambiguation). */
-  private def parseRegularMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
-    // Strip check/mate/capture indicators and promotion suffix (e.g. =Q)
+  private def parseRegularMove(notation: String, ctx: GameContext, color: Color): Option[Move] =
     val clean = notation
       .replace("+", "")
       .replace("#", "")
       .replace("x", "")
       .replaceAll("=[NBRQ]$", "")
 
-    // The destination square is always the last two characters
     if clean.length < 2 then None
     else
       val destStr = clean.takeRight(2)
       Square.fromAlgebraic(destStr).flatMap: toSquare =>
-        val disambig = clean.dropRight(2) // "" | "N"|"B"|"R"|"Q"|"K" | file | rank | file+rank
+        val disambig = clean.dropRight(2)
 
-        // Determine required piece type: upper-case first char = piece letter; else pawn
         val requiredPieceType: Option[PieceType] =
           if disambig.nonEmpty && disambig.head.isUpper then charToPieceType(disambig.head)
           else if clean.head.isUpper then charToPieceType(clean.head)
           else Some(PieceType.Pawn)
 
-        // Collect the disambiguation hint that remains after stripping the piece letter
         val hint =
           if disambig.nonEmpty && disambig.head.isUpper then disambig.tail
-          else disambig  // hint is file/rank info or empty
+          else disambig
 
-        // Candidate source squares: pieces of `color` that can geometrically reach `toSquare`.
-        // We prefer pieces that can actually reach the target; if none can (positionally illegal
-        // PGN input), fall back to any piece of the matching type belonging to `color`.
-        val reachable: Set[Square] =
-          board.pieces.collect {
-            case (from, piece) if piece.color == color &&
-              MoveValidator.legalTargets(board, from).contains(toSquare) => from
-          }.toSet
+        val promotion = extractPromotion(notation)
 
-        val candidates: Set[Square] =
-          if reachable.nonEmpty then reachable
-          else
-            // Fallback for positionally-illegal but syntactically valid PGN notation:
-            // find any piece of `color` with the correct piece type on the board.
-            board.pieces.collect {
-              case (from, piece) if piece.color == color => from
-            }.toSet
+        // Get all legal moves for this color that reach toSquare
+        val allLegal = StandardRules.allLegalMoves(ctx)
+        val candidates = allLegal.filter { move =>
+          move.to == toSquare &&
+          ctx.board.pieceAt(move.from).exists(p =>
+            p.color == color &&
+            requiredPieceType.forall(_ == p.pieceType)
+          ) &&
+          (hint.isEmpty || matchesHint(move.from, hint)) &&
+          promotionMatches(move, promotion)
+        }
 
-        // Filter by required piece type
-        val byPiece = candidates.filter(from =>
-          requiredPieceType.forall(pt => board.pieceAt(from).exists(_.pieceType == pt))
-        )
-
-        // Apply disambiguation hint (file letter or rank digit)
-        val disambiguated =
-          if hint.isEmpty then byPiece
-          else byPiece.filter(from => matchesHint(from, hint))
-
-        val promotion     = extractPromotion(notation)
-        val movePieceType = requiredPieceType.getOrElse(PieceType.Pawn)
-        val moveIsCapture = notation.contains('x')
-        disambiguated.headOption.map(from => HistoryMove(from, toSquare, None, promotion, movePieceType, moveIsCapture))
+        candidates.headOption
 
   /** True if `sq` matches a disambiguation hint (file letter, rank digit, or both). */
   private def matchesHint(sq: Square, hint: String): Boolean =
-    hint.forall(c => if c >= 'a' && c <= 'h' then sq.file.toString.equalsIgnoreCase(c.toString)
-    else if c >= '1' && c <= '8' then sq.rank.ordinal == (c - '1')
-    else true)
+    hint.forall(c =>
+      if c >= 'a' && c <= 'h' then sq.file.toString.equalsIgnoreCase(c.toString)
+      else if c >= '1' && c <= '8' then sq.rank.ordinal == (c - '1')
+      else true
+    )
+
+  private def promotionMatches(move: Move, promotion: Option[PromotionPiece]): Boolean =
+    promotion match
+      case None     => move.moveType == MoveType.Normal || move.moveType == MoveType.EnPassant ||
+                       move.moveType == MoveType.CastleKingside || move.moveType == MoveType.CastleQueenside
+      case Some(pp) => move.moveType == MoveType.Promotion(pp)
 
   /** Extract a promotion piece from a notation string containing =Q/=R/=B/=N. */
   private[notation] def extractPromotion(notation: String): Option[PromotionPiece] =
@@ -192,77 +172,16 @@ object PgnParser:
   /** Walk all move tokens, failing immediately on any unresolvable or illegal move. */
   private def validateMovesText(moveText: String): Either[String, List[HistoryMove]] =
     val tokens = moveText.split("\\s+").filter(_.nonEmpty)
-    tokens.foldLeft(Right((Board.initial, GameHistory.empty, Color.White, List.empty[HistoryMove])): Either[String, (Board, GameHistory, Color, List[HistoryMove])]) {
+    tokens.foldLeft(Right((GameContext.initial, Color.White, List.empty[HistoryMove])): Either[String, (GameContext, Color, List[HistoryMove])]) {
       case (acc, token) =>
-        acc.flatMap { case (board, history, color, moves) =>
-          if isMoveNumberOrResult(token) then Right((board, history, color, moves))
+        acc.flatMap { case (ctx, color, moves) =>
+          if isMoveNumberOrResult(token) then Right((ctx, color, moves))
           else
-            strictParseAlgebraicMove(token, board, history, color) match
+            parseAlgebraicMove(token, ctx, color) match
               case None       => Left(s"Illegal or impossible move: '$token'")
               case Some(move) =>
-                val newBoard   = applyMoveToBoard(board, move, color)
-                val newHistory = history.addMove(move)
-                Right((newBoard, newHistory, color.opposite, moves :+ move))
+                val histMove = toHistoryMove(move, ctx, color)
+                val nextCtx  = StandardRules.applyMove(ctx, move)
+                Right((nextCtx, color.opposite, moves :+ histMove))
         }
-    }.map(_._4)
-
-  /** Strict algebraic move parse — no fallback to positionally-illegal moves. */
-  private def strictParseAlgebraicMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
-    val rank = if color == Color.White then Rank.R1 else Rank.R8
-    notation match
-      case "O-O" | "O-O+" | "O-O#" =>
-        val dest = Square(File.G, rank)
-        Option.when(MoveValidator.castlingTargets(board, history, color).contains(dest))(
-          HistoryMove(Square(File.E, rank), dest, Some("Kingside"), pieceType = PieceType.King)
-        )
-      case "O-O-O" | "O-O-O+" | "O-O-O#" =>
-        val dest = Square(File.C, rank)
-        Option.when(MoveValidator.castlingTargets(board, history, color).contains(dest))(
-          HistoryMove(Square(File.E, rank), dest, Some("Queenside"), pieceType = PieceType.King)
-        )
-      case _ =>
-        strictParseRegularMove(notation, board, history, color)
-
-  /** Strict regular move parse — uses only legally reachable squares, no fallback. */
-  private def strictParseRegularMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
-    val clean = notation
-      .replace("+", "")
-      .replace("#", "")
-      .replace("x", "")
-      .replaceAll("=[NBRQ]$", "")
-
-    if clean.length < 2 then None
-    else
-      val destStr = clean.takeRight(2)
-      Square.fromAlgebraic(destStr).flatMap { toSquare =>
-        val disambig = clean.dropRight(2)
-
-        val requiredPieceType: Option[PieceType] =
-          if disambig.nonEmpty && disambig.head.isUpper then charToPieceType(disambig.head)
-          else if clean.head.isUpper then charToPieceType(clean.head)
-          else Some(PieceType.Pawn)
-
-        val hint =
-          if disambig.nonEmpty && disambig.head.isUpper then disambig.tail
-          else disambig
-
-        // Strict: only squares from which a legal move (including en passant/castling awareness) exists.
-        val reachable: Set[Square] =
-          board.pieces.collect {
-            case (from, piece) if piece.color == color &&
-              MoveValidator.legalTargets(board, history, from).contains(toSquare) => from
-          }.toSet
-
-        val byPiece = reachable.filter(from =>
-          requiredPieceType.forall(pt => board.pieceAt(from).exists(_.pieceType == pt))
-        )
-
-        val disambiguated =
-          if hint.isEmpty then byPiece
-          else byPiece.filter(from => matchesHint(from, hint))
-
-        val promotion     = extractPromotion(notation)
-        val movePieceType = requiredPieceType.getOrElse(PieceType.Pawn)
-        val moveIsCapture = notation.contains('x')
-        disambiguated.headOption.map(from => HistoryMove(from, toSquare, None, promotion, movePieceType, moveIsCapture))
-      }
+    }.map(_._3)
diff --git a/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerBranchTest.scala b/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerBranchTest.scala
index b8ab9a4..5685c87 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerBranchTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerBranchTest.scala
@@ -1,38 +1,32 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.board.{Square, File, Rank}
+import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
 class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
-  
+
   private def sq(f: File, r: Rank): Square = Square(f, r)
 
-  // ──── Helper: Command that always fails ────
   private case class FailingCommand() extends Command:
     override def execute(): Boolean = false
     override def undo(): Boolean = false
     override def description: String = "Failing command"
 
-  // ──── Helper: Command that conditionally fails on undo or execute ────
   private case class ConditionalFailCommand(var shouldFailOnUndo: Boolean = false, var shouldFailOnExecute: Boolean = false) extends Command:
     override def execute(): Boolean = !shouldFailOnExecute
     override def undo(): Boolean = !shouldFailOnUndo
     override def description: String = "Conditional fail"
 
   private def createMoveCommand(from: Square, to: Square, executeSucceeds: Boolean = true): MoveCommand =
-    val cmd = MoveCommand(
+    MoveCommand(
       from = from,
       to = to,
-      moveResult = if executeSucceeds then Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)) else None,
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
+      moveResult = if executeSucceeds then Some(MoveResult.Successful(GameContext.initial, None)) else None,
+      previousContext = Some(GameContext.initial)
     )
-    cmd
 
-  // ──── BRANCH: execute() returns false ────
   test("CommandInvoker.execute() with failing command returns false"):
     val invoker = new CommandInvoker()
     val cmd = FailingCommand()
@@ -44,18 +38,14 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
     val invoker = new CommandInvoker()
     val failingCmd = FailingCommand()
     val successCmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    
     invoker.execute(failingCmd) shouldBe false
     invoker.history.size shouldBe 0
-    
     invoker.execute(successCmd) shouldBe true
     invoker.history.size shouldBe 1
     invoker.history(0) shouldBe successCmd
 
-  // ──── BRANCH: undo() with invalid index (currentIndex < 0) ────
   test("CommandInvoker.undo() returns false when currentIndex < 0"):
     val invoker = new CommandInvoker()
-    // currentIndex starts at -1
     invoker.undo() shouldBe false
 
   test("CommandInvoker.undo() returns false when empty history"):
@@ -63,41 +53,31 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
     invoker.canUndo shouldBe false
     invoker.undo() shouldBe false
 
-  // ──── BRANCH: undo() with invalid index (currentIndex >= size) ────
   test("CommandInvoker.undo() returns false when currentIndex >= history size"):
     val invoker = new CommandInvoker()
     val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    
     invoker.execute(cmd1)
     invoker.execute(cmd2)
-    // currentIndex now = 1, history.size = 2
-    
-    invoker.undo()  // currentIndex becomes 0
-    invoker.undo()  // currentIndex becomes -1
-    invoker.undo()  // currentIndex still -1, should fail
+    invoker.undo()
+    invoker.undo()
+    invoker.undo()
 
-  // ──── BRANCH: undo() command returns false ────
   test("CommandInvoker.undo() returns false when command.undo() fails"):
     val invoker = new CommandInvoker()
     val failingCmd = ConditionalFailCommand(shouldFailOnUndo = true)
-    
     invoker.execute(failingCmd) shouldBe true
     invoker.canUndo shouldBe true
-    
     invoker.undo() shouldBe false
-    // Index should not change when undo fails
     invoker.getCurrentIndex shouldBe 0
 
   test("CommandInvoker.undo() returns true when command.undo() succeeds"):
     val invoker = new CommandInvoker()
     val successCmd = ConditionalFailCommand(shouldFailOnUndo = false)
-    
     invoker.execute(successCmd) shouldBe true
     invoker.undo() shouldBe true
     invoker.getCurrentIndex shouldBe -1
 
-  // ──── BRANCH: redo() with invalid index (currentIndex + 1 >= size) ────
   test("CommandInvoker.redo() returns false when nothing to redo"):
     val invoker = new CommandInvoker()
     invoker.redo() shouldBe false
@@ -105,9 +85,7 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
   test("CommandInvoker.redo() returns false when at end of history"):
     val invoker = new CommandInvoker()
     val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    
     invoker.execute(cmd)
-    // currentIndex = 0, history.size = 1
     invoker.canRedo shouldBe false
     invoker.redo() shouldBe false
 
@@ -115,59 +93,41 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
     val invoker = new CommandInvoker()
     val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    
     invoker.execute(cmd1)
     invoker.execute(cmd2)
-    // currentIndex = 1, size = 2, currentIndex + 1 = 2, so 2 < 2 is false
     invoker.canRedo shouldBe false
     invoker.redo() shouldBe false
 
-  // ──── BRANCH: redo() command returns false ────
   test("CommandInvoker.redo() returns false when command.execute() fails"):
     val invoker = new CommandInvoker()
     val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val redoFailCmd = ConditionalFailCommand(shouldFailOnExecute = false)  // Succeeds on first execute
-    
+    val redoFailCmd = ConditionalFailCommand(shouldFailOnExecute = false)
     invoker.execute(cmd1)
-    invoker.execute(redoFailCmd)  // Succeeds and added to history
-    
+    invoker.execute(redoFailCmd)
     invoker.undo()
-    // currentIndex = 0, redoFailCmd is at index 1
     invoker.canRedo shouldBe true
-    
-    // Now modify to fail on next execute (redo)
     redoFailCmd.shouldFailOnExecute = true
     invoker.redo() shouldBe false
-    // currentIndex should not change
     invoker.getCurrentIndex shouldBe 0
 
   test("CommandInvoker.redo() returns true when command.execute() succeeds"):
     val invoker = new CommandInvoker()
     val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    
     invoker.execute(cmd) shouldBe true
     invoker.undo() shouldBe true
     invoker.redo() shouldBe true
     invoker.getCurrentIndex shouldBe 0
 
-  // ──── BRANCH: execute() with redo history discarding (while loop) ────
   test("CommandInvoker.execute() discards redo history via while loop"):
     val invoker = new CommandInvoker()
     val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
     val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    
     invoker.execute(cmd1)
     invoker.execute(cmd2)
-    // currentIndex = 1, size = 2
-    
     invoker.undo()
-    // currentIndex = 0, size = 2
-    // Redo history exists: cmd2 is at index 1
     invoker.canRedo shouldBe true
-    
     invoker.execute(cmd3)
-    // while loop should discard cmd2
     invoker.canRedo shouldBe false
     invoker.history.size shouldBe 2
     invoker.history(1) shouldBe cmd3
@@ -178,39 +138,25 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
     val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
     val cmd3 = createMoveCommand(sq(File.G, Rank.R1), sq(File.F, Rank.R3))
     val cmd4 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    
     invoker.execute(cmd1)
     invoker.execute(cmd2)
     invoker.execute(cmd3)
     invoker.execute(cmd4)
-    // currentIndex = 3, size = 4
-    
     invoker.undo()
     invoker.undo()
-    // currentIndex = 1, size = 4
-    // Redo history: cmd3 (idx 2), cmd4 (idx 3)
     invoker.canRedo shouldBe true
-    
     val newCmd = createMoveCommand(sq(File.B, Rank.R2), sq(File.B, Rank.R4))
     invoker.execute(newCmd)
-    // While loop should discard indices 2 and 3 (cmd3 and cmd4)
     invoker.history.size shouldBe 3
     invoker.canRedo shouldBe false
 
-  // ──── BRANCH: execute() with no redo history to discard ────
   test("CommandInvoker.execute() with no redo history (while condition false)"):
     val invoker = new CommandInvoker()
     val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    
     invoker.execute(cmd1)
     invoker.execute(cmd2)
-    // currentIndex = 1, size = 2
-    // currentIndex < size - 1 is 1 < 1 which is false, so while loop doesn't run
-    
     invoker.canRedo shouldBe false
-    
     val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    invoker.execute(cmd3)  // While loop condition should be false, no iterations
+    invoker.execute(cmd3)
     invoker.history.size shouldBe 3
-
diff --git a/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerTest.scala b/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerTest.scala
index 2e06aac..7beca2d 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerTest.scala
@@ -1,22 +1,20 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.board.{Square, File, Rank}
+import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
 class CommandInvokerTest extends AnyFunSuite with Matchers:
 
   private def sq(f: File, r: Rank): Square = Square(f, r)
-  
+
   private def createMoveCommand(from: Square, to: Square): MoveCommand =
     MoveCommand(
       from = from,
       to = to,
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
+      moveResult = Some(MoveResult.Successful(GameContext.initial, None)),
+      previousContext = Some(GameContext.initial)
     )
 
   test("CommandInvoker executes a command and adds it to history"):
@@ -92,10 +90,8 @@ class CommandInvokerTest extends AnyFunSuite with Matchers:
     invoker.execute(cmd2)
     invoker.undo()
     invoker.undo()
-    // After undoing twice, we're at the beginning (before any commands)
     invoker.getCurrentIndex shouldBe -1
     invoker.canRedo shouldBe true
-    // Executing a new command from the beginning discards all redo history
     invoker.execute(cmd3)
     invoker.canRedo shouldBe false
     invoker.history.size shouldBe 1
@@ -110,14 +106,11 @@ class CommandInvokerTest extends AnyFunSuite with Matchers:
     invoker.execute(cmd1)
     invoker.execute(cmd2)
     invoker.undo()
-    // After one undo, we're at the end of cmd1
     invoker.getCurrentIndex shouldBe 0
     invoker.canRedo shouldBe true
-    // Executing a new command discards cmd2 (the redo history)
     invoker.execute(cmd3)
     invoker.canRedo shouldBe false
     invoker.history.size shouldBe 2
     invoker.history(0) shouldBe cmd1
     invoker.history(1) shouldBe cmd3
     invoker.getCurrentIndex shouldBe 1
-
diff --git a/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerThreadSafetyTest.scala b/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerThreadSafetyTest.scala
index 8b6215d..a3970d3 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerThreadSafetyTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerThreadSafetyTest.scala
@@ -1,7 +1,7 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.board.{Square, File, Rank}
+import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 import scala.collection.mutable
@@ -14,10 +14,8 @@ class CommandInvokerThreadSafetyTest extends AnyFunSuite with Matchers:
     MoveCommand(
       from = from,
       to = to,
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
+      moveResult = Some(MoveResult.Successful(GameContext.initial, None)),
+      previousContext = Some(GameContext.initial)
     )
 
   test("CommandInvoker is thread-safe for concurrent execute and history reads"):
@@ -25,15 +23,11 @@ class CommandInvokerThreadSafetyTest extends AnyFunSuite with Matchers:
     @volatile var raceDetected = false
     val exceptions = mutable.ListBuffer[Exception]()
 
-    // Thread 1: executes commands
     val executorThread = new Thread(new Runnable {
       def run(): Unit = {
         try {
           for i <- 1 to 1000 do
-            val cmd = createMoveCommand(
-              sq(File.E, Rank.R2),
-              sq(File.E, Rank.R4)
-            )
+            val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
             invoker.execute(cmd)
         } catch {
           case e: Exception =>
@@ -43,14 +37,13 @@ class CommandInvokerThreadSafetyTest extends AnyFunSuite with Matchers:
       }
     })
 
-    // Thread 2: reads history during execution
     val readerThread = new Thread(new Runnable {
       def run(): Unit = {
         try {
           for _ <- 1 to 1000 do
             val _ = invoker.history
             val _ = invoker.getCurrentIndex
-            Thread.sleep(0) // Yield to increase contention
+            Thread.sleep(0)
         } catch {
           case e: Exception =>
             exceptions += e
@@ -72,11 +65,9 @@ class CommandInvokerThreadSafetyTest extends AnyFunSuite with Matchers:
     @volatile var raceDetected = false
     val exceptions = mutable.ListBuffer[Exception]()
 
-    // Pre-populate with some commands
     for _ <- 1 to 5 do
       invoker.execute(createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4)))
 
-    // Thread 1: executes new commands
     val executorThread = new Thread(new Runnable {
       def run(): Unit = {
         try {
@@ -90,13 +81,11 @@ class CommandInvokerThreadSafetyTest extends AnyFunSuite with Matchers:
       }
     })
 
-    // Thread 2: undoes commands
     val undoThread = new Thread(new Runnable {
       def run(): Unit = {
         try {
           for _ <- 1 to 500 do
-            if invoker.canUndo then
-              invoker.undo()
+            if invoker.canUndo then invoker.undo()
         } catch {
           case e: Exception =>
             exceptions += e
@@ -105,13 +94,11 @@ class CommandInvokerThreadSafetyTest extends AnyFunSuite with Matchers:
       }
     })
 
-    // Thread 3: redoes commands
     val redoThread = new Thread(new Runnable {
       def run(): Unit = {
         try {
           for _ <- 1 to 500 do
-            if invoker.canRedo then
-              invoker.redo()
+            if invoker.canRedo then invoker.redo()
         } catch {
           case e: Exception =>
             exceptions += e
diff --git a/modules/core/src/test/scala/de/nowchess/chess/command/CommandTest.scala b/modules/core/src/test/scala/de/nowchess/chess/command/CommandTest.scala
index ca71cdc..5e23234 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/command/CommandTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/command/CommandTest.scala
@@ -1,7 +1,6 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -29,24 +28,15 @@ class CommandTest extends AnyFunSuite with Matchers:
     cmd.undo() shouldBe false
 
   test("ResetCommand with prior state can undo"):
-    val cmd = ResetCommand(
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
+    val cmd = ResetCommand(previousContext = Some(GameContext.initial))
     cmd.execute() shouldBe true
     cmd.undo() shouldBe true
 
-  test("ResetCommand with partial state cannot undo"):
-    val cmd = ResetCommand(
-      previousBoard = Some(Board.initial),
-      previousHistory = None,  // missing
-      previousTurn = Some(Color.White)
-    )
+  test("ResetCommand with no context cannot undo"):
+    val cmd = ResetCommand(previousContext = None)
     cmd.execute() shouldBe true
     cmd.undo() shouldBe false
 
   test("ResetCommand description"):
     val cmd = ResetCommand()
     cmd.description shouldBe "Reset board"
-
diff --git a/modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandDefaultsTest.scala b/modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandDefaultsTest.scala
new file mode 100644
index 0000000..cd33940
--- /dev/null
+++ b/modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandDefaultsTest.scala
@@ -0,0 +1,54 @@
+package de.nowchess.chess.command
+
+import de.nowchess.api.board.{Square, File, Rank}
+import de.nowchess.api.game.GameContext
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class MoveCommandDefaultsTest extends AnyFunSuite with Matchers:
+
+  private def sq(f: File, r: Rank): Square = Square(f, r)
+
+  test("MoveCommand with no moveResult defaults to None"):
+    val cmd = MoveCommand(from = sq(File.E, Rank.R2), to = sq(File.E, Rank.R4))
+    cmd.moveResult shouldBe None
+    cmd.execute() shouldBe false
+
+  test("MoveCommand with no previousContext defaults to None"):
+    val cmd = MoveCommand(from = sq(File.E, Rank.R2), to = sq(File.E, Rank.R4))
+    cmd.previousContext shouldBe None
+    cmd.undo() shouldBe false
+
+  test("MoveCommand description is always returned"):
+    val cmd = MoveCommand(from = sq(File.E, Rank.R2), to = sq(File.E, Rank.R4))
+    cmd.description shouldBe "Move from e2 to e4"
+
+  test("MoveCommand execute returns false when moveResult is None"):
+    val cmd = MoveCommand(from = sq(File.A, Rank.R1), to = sq(File.B, Rank.R3))
+    cmd.execute() shouldBe false
+
+  test("MoveCommand undo returns false when previousContext is None"):
+    val cmd = MoveCommand(
+      from = sq(File.E, Rank.R2),
+      to = sq(File.E, Rank.R4),
+      moveResult = Some(MoveResult.Successful(GameContext.initial, None)),
+      previousContext = None
+    )
+    cmd.undo() shouldBe false
+
+  test("MoveCommand execute returns true when moveResult is defined"):
+    val cmd = MoveCommand(
+      from = sq(File.E, Rank.R2),
+      to = sq(File.E, Rank.R4),
+      moveResult = Some(MoveResult.Successful(GameContext.initial, None))
+    )
+    cmd.execute() shouldBe true
+
+  test("MoveCommand undo returns true when previousContext is defined"):
+    val cmd = MoveCommand(
+      from = sq(File.E, Rank.R2),
+      to = sq(File.E, Rank.R4),
+      moveResult = Some(MoveResult.Successful(GameContext.initial, None)),
+      previousContext = Some(GameContext.initial)
+    )
+    cmd.undo() shouldBe true
diff --git a/modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandImmutabilityTest.scala b/modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandImmutabilityTest.scala
index b23350a..f182489 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandImmutabilityTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandImmutabilityTest.scala
@@ -1,7 +1,7 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.board.{Square, File, Rank}
+import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -10,56 +10,38 @@ class MoveCommandImmutabilityTest extends AnyFunSuite with Matchers:
   private def sq(f: File, r: Rank): Square = Square(f, r)
 
   test("MoveCommand should be immutable - fields cannot be mutated after creation"):
-    val cmd1 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
+    val cmd1 = MoveCommand(from = sq(File.E, Rank.R2), to = sq(File.E, Rank.R4))
 
-    // Create second command with filled state
-    val result = MoveResult.Successful(Board.initial, GameHistory.empty, Color.Black, None)
+    val result = MoveResult.Successful(GameContext.initial, None)
     val cmd2 = cmd1.copy(
       moveResult = Some(result),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
+      previousContext = Some(GameContext.initial)
     )
 
-    // Original should be unchanged
     cmd1.moveResult shouldBe None
-    cmd1.previousBoard shouldBe None
-    cmd1.previousHistory shouldBe None
-    cmd1.previousTurn shouldBe None
+    cmd1.previousContext shouldBe None
 
-    // New should have values
     cmd2.moveResult shouldBe Some(result)
-    cmd2.previousBoard shouldBe Some(Board.initial)
-    cmd2.previousHistory shouldBe Some(GameHistory.empty)
-    cmd2.previousTurn shouldBe Some(Color.White)
+    cmd2.previousContext shouldBe Some(GameContext.initial)
 
   test("MoveCommand equals and hashCode respect immutability"):
     val cmd1 = MoveCommand(
       from = sq(File.E, Rank.R2),
       to = sq(File.E, Rank.R4),
       moveResult = None,
-      previousBoard = None,
-      previousHistory = None,
-      previousTurn = None
+      previousContext = None
     )
 
     val cmd2 = MoveCommand(
       from = sq(File.E, Rank.R2),
       to = sq(File.E, Rank.R4),
       moveResult = None,
-      previousBoard = None,
-      previousHistory = None,
-      previousTurn = None
+      previousContext = None
     )
 
-    // Same values should be equal
     cmd1 shouldBe cmd2
     cmd1.hashCode shouldBe cmd2.hashCode
 
-    // Hash should be consistent (required for use as map keys)
     val hash1 = cmd1.hashCode
     val hash2 = cmd1.hashCode
     hash1 shouldBe hash2
diff --git a/modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala b/modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala
deleted file mode 100644
index 3ec0330..0000000
--- a/modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala
+++ /dev/null
@@ -1,526 +0,0 @@
-package de.nowchess.chess.controller
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.CastlingRights
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{CastleSide, GameHistory}
-import de.nowchess.chess.notation.FenParser
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameControllerTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-  private def processMove(board: Board, history: GameHistory, turn: Color, raw: String): MoveResult =
-    GameController.processMove(board, history, turn, raw)
-
-  private def castlingRights(history: GameHistory, color: Color): CastlingRights =
-    de.nowchess.chess.logic.CastlingRightsCalculator.deriveCastlingRights(history, color)
-
-  // ──── processMove ────────────────────────────────────────────────────
-
-  test("processMove: 'quit' input returns Quit"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "quit") shouldBe MoveResult.Quit
-
-  test("processMove: 'q' input returns Quit"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "q") shouldBe MoveResult.Quit
-
-  test("processMove: quit with surrounding whitespace returns Quit"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "  quit  ") shouldBe MoveResult.Quit
-
-  test("processMove: unparseable input returns InvalidFormat"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "xyz") shouldBe MoveResult.InvalidFormat("xyz")
-
-  test("processMove: valid format but empty square returns NoPiece"):
-    // E3 is empty in the initial position
-    processMove(Board.initial, GameHistory.empty, Color.White, "e3e4") shouldBe MoveResult.NoPiece
-
-  test("processMove: piece of wrong color returns WrongColor"):
-    // E7 has a Black pawn; it is White's turn
-    processMove(Board.initial, GameHistory.empty, Color.White, "e7e6") shouldBe MoveResult.WrongColor
-
-  test("processMove: geometrically illegal move returns IllegalMove"):
-    // White pawn at E2 cannot jump three squares to E5
-    processMove(Board.initial, GameHistory.empty, Color.White, "e2e5") shouldBe MoveResult.IllegalMove
-
-  test("processMove: move that leaves own king in check returns IllegalMove"):
-    // White King E1 is in check from Black Rook E8. Moving the D2 pawn is
-    // geometrically legal but does not resolve the check — must be rejected.
-    val b = Board(Map(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.D, Rank.R2) -> Piece.WhitePawn,
-      sq(File.E, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "d2d4") shouldBe MoveResult.IllegalMove
-
-  test("processMove: move that resolves check is allowed"):
-    // White King E1 is in check from Black Rook E8 along the E-file.
-    // White Rook A5 interposes at E5 — resolves the check, no new check on Black King A8.
-    val b = Board(Map(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R5) -> Piece.WhiteRook,
-      sq(File.E, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "a5e5") match
-      case _: MoveResult.Moved => succeed
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: legal pawn move returns Moved with updated board and flipped turn"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "e2e4") match
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        newBoard.pieceAt(sq(File.E, Rank.R4)) shouldBe Some(Piece.WhitePawn)
-        newBoard.pieceAt(sq(File.E, Rank.R2)) shouldBe None
-        captured shouldBe None
-        newTurn shouldBe Color.Black
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: legal capture returns Moved with the captured piece"):
-    val board = Board(Map(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R6) -> Piece.BlackPawn,
-      sq(File.H, Rank.R1) -> Piece.BlackKing,
-      sq(File.H, Rank.R8) -> Piece.WhiteKing
-    ))
-    processMove(board, GameHistory.empty, Color.White, "e5d6") match
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        captured shouldBe Some(Piece.BlackPawn)
-        newBoard.pieceAt(sq(File.D, Rank.R6)) shouldBe Some(Piece.WhitePawn)
-        newTurn shouldBe Color.Black
-      case other => fail(s"Expected Moved, got $other")
-
-  // ──── processMove: check / checkmate / stalemate ─────────────────────
-
-  test("processMove: legal move that delivers check returns MovedInCheck"):
-    // White Ra1, Ka3; Black Kh8 — White plays Ra1-Ra8, Ra8 attacks rank 8 putting Kh8 in check
-    // Kh8 can escape to g7/g8/h7 so this is InCheck, not Mated
-    val b = Board(Map(
-      sq(File.A, Rank.R1) -> Piece.WhiteRook,
-      sq(File.C, Rank.R3) -> Piece.WhiteKing,
-      sq(File.H, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "a1a8") match
-      case MoveResult.MovedInCheck(_, _, _, newTurn) => newTurn shouldBe Color.Black
-      case other => fail(s"Expected MovedInCheck, got $other")
-
-  test("processMove: legal move that results in checkmate returns Checkmate"):
-    // White Qa1, Ka6; Black Ka8 — White plays Qa1-Qh8 (diagonal a1→h8)
-    // After Qh8: White Qh8 + Ka6 vs Black Ka8 = checkmate (spec-verified position)
-    // Qa1 does NOT currently attack Ka8 — path along file A is blocked by Ka6
-    val b = Board(Map(
-      sq(File.A, Rank.R1) -> Piece.WhiteQueen,
-      sq(File.A, Rank.R6) -> Piece.WhiteKing,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "a1h8") match
-      case MoveResult.Checkmate(winner) => winner shouldBe Color.White
-      case other => fail(s"Expected Checkmate(White), got $other")
-
-  test("processMove: legal move that results in stalemate returns Stalemate"):
-    // White Qb1, Kc6; Black Ka8 — White plays Qb1-Qb6
-    // After Qb6: White Qb6 + Kc6 vs Black Ka8 = stalemate (spec-verified position)
-    val b = Board(Map(
-      sq(File.B, Rank.R1) -> Piece.WhiteQueen,
-      sq(File.C, Rank.R6) -> Piece.WhiteKing,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "b1b6") match
-      case MoveResult.Stalemate => succeed
-      case other => fail(s"Expected Stalemate, got $other")
-
-  // ──── castling execution ─────────────────────────────────────────────
-
-  test("processMove: e1g1 returns Moved with king on g1 and rook on f1"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1g1") match
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        newBoard.pieceAt(sq(File.G, Rank.R1)) shouldBe Some(Piece.WhiteKing)
-        newBoard.pieceAt(sq(File.F, Rank.R1)) shouldBe Some(Piece.WhiteRook)
-        newBoard.pieceAt(sq(File.E, Rank.R1)) shouldBe None
-        newBoard.pieceAt(sq(File.H, Rank.R1)) shouldBe None
-        captured shouldBe None
-        newTurn shouldBe Color.Black
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: e1c1 returns Moved with king on c1 and rook on d1"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.A, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1c1") match
-      case MoveResult.Moved(newBoard, _, _, _) =>
-        newBoard.pieceAt(sq(File.C, Rank.R1)) shouldBe Some(Piece.WhiteKing)
-        newBoard.pieceAt(sq(File.D, Rank.R1)) shouldBe Some(Piece.WhiteRook)
-      case other => fail(s"Expected Moved, got $other")
-
-  // ──── rights revocation ──────────────────────────────────────────────
-
-  test("processMove: e1g1 revokes both white castling rights"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1g1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White) shouldBe CastlingRights.None
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: moving rook from h1 revokes white kingside right"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "h1h4") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide  shouldBe false
-        castlingRights(newHistory, Color.White).queenSide shouldBe true
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide  shouldBe false
-        castlingRights(newHistory, Color.White).queenSide shouldBe true
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  test("processMove: moving king from e1 revokes both white rights"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1e2") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White) shouldBe CastlingRights.None
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: enemy capture on h1 revokes white kingside right"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R2) -> Piece.BlackRook,
-        sq(File.A, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "h2h1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide shouldBe false
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide shouldBe false
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  test("processMove: castle attempt when rights revoked returns IllegalMove"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R1), sq(File.E, Rank.R2)).addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R1))
-    processMove(b, history, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
-
-  test("processMove: castle attempt when rook not on home square returns IllegalMove"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.G, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
-
-  test("processMove: moving king from e8 revokes both black rights"):
-    val b = Board(Map(
-        sq(File.E, Rank.R8) -> Piece.BlackKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "e8e7") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black) shouldBe CastlingRights.None
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black) shouldBe CastlingRights.None
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  test("processMove: moving rook from a8 revokes black queenside right"):
-    val b = Board(Map(
-        sq(File.E, Rank.R8) -> Piece.BlackKing,
-        sq(File.A, Rank.R8) -> Piece.BlackRook,
-        sq(File.H, Rank.R1) -> Piece.WhiteKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "a8a1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).queenSide shouldBe false
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe true
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).queenSide shouldBe false
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe true
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  test("processMove: moving rook from h8 revokes black kingside right"):
-    val b = Board(Map(
-        sq(File.E, Rank.R8) -> Piece.BlackKing,
-        sq(File.H, Rank.R8) -> Piece.BlackRook,
-        sq(File.A, Rank.R1) -> Piece.WhiteKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "h8h4") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe false
-        castlingRights(newHistory, Color.Black).queenSide shouldBe true
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe false
-        castlingRights(newHistory, Color.Black).queenSide shouldBe true
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  test("processMove: enemy capture on a1 revokes white queenside right"):
-    val b = Board(Map(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.A, Rank.R1) -> Piece.WhiteRook,
-        sq(File.A, Rank.R2) -> Piece.BlackRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "a2a1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).queenSide shouldBe false
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).queenSide shouldBe false
-      case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  // ──── en passant ────────────────────────────────────────────────────────
-
-  test("en passant capture removes the captured pawn from the board"):
-    // Setup: white pawn e5, black pawn just double-pushed to d5 (ep target = d6)
-    val b = Board(Map(
-      Square(File.E, Rank.R5) -> Piece.WhitePawn,
-      Square(File.D, Rank.R5) -> Piece.BlackPawn,
-      Square(File.E, Rank.R1) -> Piece.WhiteKing,
-      Square(File.E, Rank.R8) -> Piece.BlackKing
-    ))
-    val h = GameHistory.empty.addMove(Square(File.D, Rank.R7), Square(File.D, Rank.R5))
-    val result = GameController.processMove(b, h, Color.White, "e5d6")
-    result match
-      case MoveResult.Moved(newBoard, _, captured, _) =>
-        newBoard.pieceAt(Square(File.D, Rank.R5)) shouldBe None  // captured pawn removed
-        newBoard.pieceAt(Square(File.D, Rank.R6)) shouldBe Some(Piece.WhitePawn)  // capturing pawn placed
-        captured shouldBe Some(Piece.BlackPawn)
-      case other => fail(s"Expected Moved but got $other")
-
-  test("en passant capture by black removes the captured white pawn"):
-    // Setup: black pawn d4, white pawn just double-pushed to e4 (ep target = e3)
-    val b = Board(Map(
-      Square(File.D, Rank.R4) -> Piece.BlackPawn,
-      Square(File.E, Rank.R4) -> Piece.WhitePawn,
-      Square(File.E, Rank.R8) -> Piece.BlackKing,
-      Square(File.E, Rank.R1) -> Piece.WhiteKing
-    ))
-    val h = GameHistory.empty.addMove(Square(File.E, Rank.R2), Square(File.E, Rank.R4))
-    val result = GameController.processMove(b, h, Color.Black, "d4e3")
-    result match
-      case MoveResult.Moved(newBoard, _, captured, _) =>
-        newBoard.pieceAt(Square(File.E, Rank.R4)) shouldBe None  // captured pawn removed
-        newBoard.pieceAt(Square(File.E, Rank.R3)) shouldBe Some(Piece.BlackPawn)  // capturing pawn placed
-        captured shouldBe Some(Piece.WhitePawn)
-      case other => fail(s"Expected Moved but got $other")
-
-  // ──── pawn promotion detection ───────────────────────────────────────────
-
-  test("processMove detects white pawn reaching R8 and returns PromotionRequired"):
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = GameController.processMove(board, GameHistory.empty, Color.White, "e7e8")
-    result should matchPattern { case _: MoveResult.PromotionRequired => }
-    result match
-      case MoveResult.PromotionRequired(from, to, _, _, _, turn) =>
-        from should be (sq(File.E, Rank.R7))
-        to   should be (sq(File.E, Rank.R8))
-        turn should be (Color.White)
-      case _ => fail("Expected PromotionRequired")
-
-  test("processMove detects black pawn reaching R1 and returns PromotionRequired"):
-    val board = FenParser.parseBoard("8/8/8/8/4K3/8/4p3/8").get
-    val result = GameController.processMove(board, GameHistory.empty, Color.Black, "e2e1")
-    result should matchPattern { case _: MoveResult.PromotionRequired => }
-    result match
-      case MoveResult.PromotionRequired(from, to, _, _, _, turn) =>
-        from should be (sq(File.E, Rank.R2))
-        to   should be (sq(File.E, Rank.R1))
-        turn should be (Color.Black)
-      case _ => fail("Expected PromotionRequired")
-
-  test("processMove detects pawn capturing to back rank as PromotionRequired with captured piece"):
-    val board = FenParser.parseBoard("3q4/4P3/8/8/8/8/8/8").get
-    val result = GameController.processMove(board, GameHistory.empty, Color.White, "e7d8")
-    result should matchPattern { case _: MoveResult.PromotionRequired => }
-    result match
-      case MoveResult.PromotionRequired(_, _, _, _, captured, _) =>
-        captured should be (Some(Piece(Color.Black, PieceType.Queen)))
-      case _ => fail("Expected PromotionRequired")
-
-  // ──── completePromotion ──────────────────────────────────────────────────
-
-  test("completePromotion applies move and places queen"):
-    // Black king on h1: not attacked by queen on e8 (different file, rank, and diagonals)
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/8/7k").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result should matchPattern { case _: MoveResult.Moved => }
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-        newBoard.pieceAt(sq(File.E, Rank.R7)) should be (None)
-        newHistory.moves should have length 1
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))
-      case _ => fail("Expected Moved")
-
-  test("completePromotion with rook underpromotion"):
-    // Black king on h1: not attacked by rook on e8 (different file and rank)
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/8/7k").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Rook, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Rook)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Rook))
-      case _ => fail("Expected Moved with Rook")
-
-  test("completePromotion with bishop underpromotion"):
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Bishop, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Bishop)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Bishop))
-      case _ => fail("Expected Moved with Bishop")
-
-  test("completePromotion with knight underpromotion"):
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Knight, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Knight)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Knight))
-      case _ => fail("Expected Moved with Knight")
-
-  test("completePromotion captures opponent piece"):
-    // Black king on h1: after white queen captures d8 queen, h1 king is safe (queen on d8 does not attack h1)
-    val board = FenParser.parseBoard("3q4/4P3/8/8/8/8/8/7k").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.D, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, _, captured, _) =>
-        newBoard.pieceAt(sq(File.D, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-        captured should be (Some(Piece(Color.Black, PieceType.Queen)))
-      case _ => fail("Expected Moved with captured piece")
-
-  test("completePromotion for black pawn to R1"):
-    val board = FenParser.parseBoard("8/8/8/8/4K3/8/4p3/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R2), sq(File.E, Rank.R1),
-      PromotionPiece.Knight, Color.Black
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R1)) should be (Some(Piece(Color.Black, PieceType.Knight)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Knight))
-      case _ => fail("Expected Moved")
-
-  test("completePromotion evaluates check after promotion"):
-    val board = FenParser.parseBoard("3k4/4P3/8/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result should matchPattern { case _: MoveResult.MovedInCheck => }
-
-  test("completePromotion full round-trip via processMove then completePromotion"):
-    // Black king on h1: not attacked by queen on e8
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/8/7k").get
-    GameController.processMove(board, GameHistory.empty, Color.White, "e7e8") match
-      case MoveResult.PromotionRequired(from, to, boardBefore, histBefore, _, turn) =>
-        val result = GameController.completePromotion(boardBefore, histBefore, from, to, PromotionPiece.Queen, turn)
-        result should matchPattern { case _: MoveResult.Moved => }
-        result match
-          case MoveResult.Moved(finalBoard, finalHistory, _, _) =>
-            finalBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-            finalHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))
-          case _ => fail("Expected Moved")
-      case _ => fail("Expected PromotionRequired")
-
-  test("completePromotion results in checkmate when promotion delivers checkmate"):
-    // Black king a8, white pawn h7, white king b6.
-    // After h7→h8=Q: Qh8 attacks rank 8 putting Ka8 in check;
-    // a7 covered by Kb6, b7 covered by Kb6, b8 covered by Qh8 — no escape.
-    val board = FenParser.parseBoard("k7/7P/1K6/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.H, Rank.R7), sq(File.H, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result should matchPattern { case MoveResult.Checkmate(_) => }
-    result match
-      case MoveResult.Checkmate(winner) => winner should be (Color.White)
-      case _ => fail("Expected Checkmate")
-
-  test("completePromotion results in stalemate when promotion stalemates opponent"):
-    // Black king a8, white pawn b7, white bishop c7, white king b6.
-    // After b7→b8=N: knight on b8 (doesn't check a8); a7 and b7 covered by Kb6;
-    // b8 defended by Bc7 so Ka8xb8 would walk into bishop — no legal moves.
-    val board = FenParser.parseBoard("k7/1PB5/1K6/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.B, Rank.R7), sq(File.B, Rank.R8),
-      PromotionPiece.Knight, Color.White
-    )
-    result should be (MoveResult.Stalemate)
-
-  // ──── half-move clock propagation ────────────────────────────────────
-
-  test("processMove: non-pawn non-capture increments halfMoveClock"):
-    // g1f3 is a knight move — not a pawn, not a capture
-    processMove(Board.initial, GameHistory.empty, Color.White, "g1f3") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        newHistory.halfMoveClock shouldBe 1
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: pawn move resets halfMoveClock to 0"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "e2e4") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        newHistory.halfMoveClock shouldBe 0
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: capture resets halfMoveClock to 0"):
-    // White pawn on e5, Black pawn on d6 — exd6 is a capture
-    val board = Board(Map(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R6) -> Piece.BlackPawn,
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.E, Rank.R8) -> Piece.BlackKing
-    ))
-    val history = GameHistory(halfMoveClock = 10)
-    processMove(board, history, Color.White, "e5d6") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        newHistory.halfMoveClock shouldBe 0
-      case other => fail(s"Expected Moved, got $other")
-
-  test("processMove: clock carries from previous history on non-pawn non-capture"):
-    val history = GameHistory(halfMoveClock = 5)
-    processMove(Board.initial, history, Color.White, "g1f3") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        newHistory.halfMoveClock shouldBe 6
-      case other => fail(s"Expected Moved, got $other")
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineEdgeCasesTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineEdgeCasesTest.scala
index 6843e11..053ebbb 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineEdgeCasesTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineEdgeCasesTest.scala
@@ -2,7 +2,6 @@ package de.nowchess.chess.engine
 
 import scala.collection.mutable
 import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
 import de.nowchess.chess.observer.{Observer, GameEvent, MoveExecutedEvent, CheckDetectedEvent, BoardResetEvent, InvalidMoveEvent}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
@@ -197,7 +196,6 @@ class GameEngineEdgeCasesTest extends AnyFunSuite with Matchers:
     
     // Access from synchronized methods
     val board = engine.board
-    val history = engine.history
     val turn = engine.turn
     val canUndo = engine.canUndo
     val canRedo = engine.canRedo
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala
index a6132c3..0b67094 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala
@@ -2,7 +2,6 @@ package de.nowchess.chess.engine
 
 import scala.collection.mutable
 import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
 import de.nowchess.chess.observer.{Observer, GameEvent, CheckDetectedEvent, CheckmateEvent, StalemateEvent}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
@@ -22,12 +21,11 @@ class GameEngineGameEndingTest extends AnyFunSuite with Matchers:
     
     observer.events.clear()
     engine.processUserInput("d8h4")
+
+    // Verify CheckmateEvent (engine also fires MoveExecutedEvent before CheckmateEvent)
+    observer.events.last shouldBe a[CheckmateEvent]
     
-    // Verify CheckmateEvent
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[CheckmateEvent]
-    
-    val event = observer.events.head.asInstanceOf[CheckmateEvent]
+    val event = observer.events.last.asInstanceOf[CheckmateEvent]
     event.winner shouldBe Color.Black
     
     // Board should be reset after checkmate
@@ -50,7 +48,7 @@ class GameEngineGameEndingTest extends AnyFunSuite with Matchers:
     
     val checkEvents = observer.events.collect { case e: CheckDetectedEvent => e }
     checkEvents.size shouldBe 1
-    checkEvents.head.turn shouldBe Color.Black // Black is now in check
+    checkEvents.head.context.turn shouldBe Color.Black // Black is now in check
     
   // Shortest known stalemate is 19 moves. Here is a faster one:
   // e3 a5 Qh5 Ra6 Qxa5 h5 h4 Rah6 Qxc7 f6 Qxd7+ Kf7 Qxb7 Qd3 Qxb8 Qh7 Qxc8 Kg6 Qe6
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineHandleFailedMoveTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineHandleFailedMoveTest.scala
index 6401cae..b6673bc 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineHandleFailedMoveTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineHandleFailedMoveTest.scala
@@ -2,7 +2,6 @@ package de.nowchess.chess.engine
 
 import scala.collection.mutable
 import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
 import de.nowchess.chess.observer.{Observer, GameEvent, InvalidMoveEvent}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineInvalidMovesTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineInvalidMovesTest.scala
index 2be9947..be4846a 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineInvalidMovesTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineInvalidMovesTest.scala
@@ -2,7 +2,6 @@ package de.nowchess.chess.engine
 
 import scala.collection.mutable
 import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
 import de.nowchess.chess.observer.{Observer, GameEvent, InvalidMoveEvent, MoveExecutedEvent}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadPgnTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadPgnTest.scala
index d156e4c..865ad21 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadPgnTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadPgnTest.scala
@@ -2,7 +2,6 @@ package de.nowchess.chess.engine
 
 import scala.collection.mutable
 import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
 import de.nowchess.chess.observer.*
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
@@ -14,8 +13,6 @@ class GameEngineLoadPgnTest extends AnyFunSuite with Matchers:
     def onGameEvent(event: GameEvent): Unit = events += event
     def lastEvent: GameEvent = events.last
 
-  // ── loadPgn happy path ────────────────────────────────────────────────────
-
   test("loadPgn: valid PGN returns Right and updates board/history"):
     val engine = new GameEngine()
     val pgn =
@@ -25,7 +22,7 @@ class GameEngineLoadPgnTest extends AnyFunSuite with Matchers:
 """
     val result = engine.loadPgn(pgn)
     result shouldBe Right(())
-    engine.history.moves.length shouldBe 2
+    engine.context.moves.size shouldBe 2
     engine.turn shouldBe Color.White
 
   test("loadPgn: emits PgnLoadedEvent on success"):
@@ -52,7 +49,7 @@ class GameEngineLoadPgnTest extends AnyFunSuite with Matchers:
     cap.events.clear()
     engine.undo()
     cap.events.last shouldBe a[MoveUndoneEvent]
-    engine.history.moves.length shouldBe 1
+    engine.context.moves.size shouldBe 1
 
   test("loadPgn: undo then redo restores position after PGN load"):
     val engine = new GameEngine()
@@ -65,7 +62,7 @@ class GameEngineLoadPgnTest extends AnyFunSuite with Matchers:
     engine.redo()
     cap.events.last shouldBe a[MoveRedoneEvent]
     engine.board shouldBe boardAfterLoad
-    engine.history.moves.length shouldBe 2
+    engine.context.moves.size shouldBe 2
 
   test("loadPgn: longer game loads all moves into command history"):
     val engine = new GameEngine()
@@ -75,18 +72,14 @@ class GameEngineLoadPgnTest extends AnyFunSuite with Matchers:
 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6
 """
     engine.loadPgn(pgn) shouldBe Right(())
-    engine.history.moves.length shouldBe 6
+    engine.context.moves.size shouldBe 6
     engine.commandHistory.length shouldBe 6
 
   test("loadPgn: invalid PGN returns Left and does not change state"):
     val engine  = new GameEngine()
-    val initial = engine.board
     val result  = engine.loadPgn("[Event \"T\"]\n\n1. Qd4\n")
     result.isLeft shouldBe true
-    // state is reset to initial (reset happens before replay, which fails)
-    engine.history.moves shouldBe empty
-
-  // ── undo/redo notation events ─────────────────────────────────────────────
+    engine.context.moves shouldBe empty
 
   test("undo emits MoveUndoneEvent with pgnNotation"):
     val engine = new GameEngine()
@@ -98,7 +91,7 @@ class GameEngineLoadPgnTest extends AnyFunSuite with Matchers:
     cap.events.last shouldBe a[MoveUndoneEvent]
     val evt = cap.events.last.asInstanceOf[MoveUndoneEvent]
     evt.pgnNotation should not be empty
-    evt.pgnNotation shouldBe "e4"  // pawn to e4
+    evt.pgnNotation shouldBe "e4"
 
   test("redo emits MoveRedoneEvent with pgnNotation"):
     val engine = new GameEngine()
@@ -113,17 +106,10 @@ class GameEngineLoadPgnTest extends AnyFunSuite with Matchers:
     evt.pgnNotation should not be empty
     evt.pgnNotation shouldBe "e4"
 
-  test("undo emits MoveUndoneEvent with empty notation when history is empty (after checkmate reset)"):
-    // Simulate state where canUndo=true but currentHistory is empty (board reset on checkmate).
-    // We achieve this by examining the branch: provide a MoveCommand with empty history saved.
-    // The simplest proxy: undo a move that reset history (stalemate/checkmate). We'll
-    // use a contrived engine state by direct command manipulation — instead, just verify
-    // that after a normal move-and-undo the notation is present; the empty-history branch
-    // is exercised internally when gameEnd resets state. We cover it via a castling undo.
+  test("undo emits MoveUndoneEvent with O-O notation for castling"):
     val engine = new GameEngine()
     val cap    = new EventCapture()
     engine.subscribe(cap)
-    // Play moves that let white castle kingside: e4 e5 Nf3 Nc6 Bc4 Bc5 O-O
     engine.processUserInput("e2e4")
     engine.processUserInput("e7e5")
     engine.processUserInput("g1f3")
@@ -140,7 +126,6 @@ class GameEngineLoadPgnTest extends AnyFunSuite with Matchers:
     val engine = new GameEngine()
     val cap    = new EventCapture()
     engine.subscribe(cap)
-    // White builds a capture on the a-file: b4, ... a6, b5, ... h6, bxa6
     engine.processUserInput("b2b4")
     engine.processUserInput("a7a6")
     engine.processUserInput("b4b5")
@@ -159,7 +144,6 @@ class GameEngineLoadPgnTest extends AnyFunSuite with Matchers:
     engine.processUserInput("e2e4")
     val pgn = "[Event \"T\"]\n\n1. d4 d5\n"
     engine.loadPgn(pgn) shouldBe Right(())
-    // First move should be d4, not e4
-    engine.history.moves.head.to shouldBe de.nowchess.api.board.Square(
+    engine.context.moves.head.to shouldBe de.nowchess.api.board.Square(
       de.nowchess.api.board.File.D, de.nowchess.api.board.Rank.R4
     )
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala
index c40c392..cf74f7d 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala
@@ -1,8 +1,8 @@
 package de.nowchess.chess.engine
 
 import de.nowchess.api.board.{Board, Color, File, Piece, PieceType, Rank, Square}
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.{MoveType, PromotionPiece}
 import de.nowchess.chess.notation.FenParser
 import de.nowchess.chess.observer.*
 import org.scalatest.funsuite.AnyFunSuite
@@ -17,9 +17,12 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
     engine.subscribe(new Observer { def onGameEvent(e: GameEvent): Unit = events += e })
     events
 
+  private def engineWith(board: Board, turn: Color = Color.White): GameEngine =
+    new GameEngine(initialContext = GameContext.initial.withBoard(board).withTurn(turn))
+
   test("processUserInput fires PromotionRequiredEvent when pawn reaches back rank") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
+    val engine = engineWith(promotionBoard)
     val events = captureEvents(engine)
 
     engine.processUserInput("e7e8")
@@ -30,7 +33,7 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
 
   test("isPendingPromotion is true after PromotionRequired input") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
+    val engine = engineWith(promotionBoard)
     captureEvents(engine)
 
     engine.processUserInput("e7e8")
@@ -45,7 +48,7 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
 
   test("completePromotion fires MoveExecutedEvent with promoted piece") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
+    val engine = engineWith(promotionBoard)
     val events = captureEvents(engine)
 
     engine.processUserInput("e7e8")
@@ -54,13 +57,13 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
     engine.isPendingPromotion should be (false)
     engine.board.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
     engine.board.pieceAt(sq(File.E, Rank.R7)) should be (None)
-    engine.history.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))
+    engine.context.moves.last.moveType shouldBe MoveType.Promotion(PromotionPiece.Queen)
     events.exists(_.isInstanceOf[MoveExecutedEvent]) should be (true)
   }
 
   test("completePromotion with rook underpromotion") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
+    val engine = engineWith(promotionBoard)
     captureEvents(engine)
 
     engine.processUserInput("e7e8")
@@ -81,7 +84,7 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
 
   test("completePromotion fires CheckDetectedEvent when promotion gives check") {
     val promotionBoard = FenParser.parseBoard("3k4/4P3/8/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
+    val engine = engineWith(promotionBoard)
     val events = captureEvents(engine)
 
     engine.processUserInput("e7e8")
@@ -91,9 +94,8 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
   }
 
   test("completePromotion results in Moved when promotion doesn't give check") {
-    // White pawn on e7, black king on a2 (far away, not in check after promotion)
     val board = FenParser.parseBoard("8/4P3/8/8/8/8/k7/8").get
-    val engine = new GameEngine(initialBoard = board)
+    val engine = engineWith(board)
     val events = captureEvents(engine)
 
     engine.processUserInput("e7e8")
@@ -106,10 +108,8 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
   }
 
   test("completePromotion results in Checkmate when promotion delivers checkmate") {
-    // Black king on a8, white king on b6, white pawn on h7
-    // h7->h8=Q delivers checkmate
     val board = FenParser.parseBoard("k7/7P/1K6/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = board)
+    val engine = engineWith(board)
     val events = captureEvents(engine)
 
     engine.processUserInput("h7h8")
@@ -120,10 +120,8 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
   }
 
   test("completePromotion results in Stalemate when promotion creates stalemate") {
-    // Black king on a8, white pawn on b7, white bishop on c7, white king on b6
-    // b7->b8=N: no check; Ka8 has no legal moves -> stalemate
     val board = FenParser.parseBoard("k7/1PB5/1K6/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = board)
+    val engine = engineWith(board)
     val events = captureEvents(engine)
 
     engine.processUserInput("b7b8")
@@ -134,10 +132,8 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
   }
 
   test("completePromotion with black pawn promotion results in Moved") {
-    // Black pawn e2, white king h3 (not on rank 1 or file e), black king a8
-    // e2->e1=Q: queen on e1 does not attack h3 -> normal Moved
     val board = FenParser.parseBoard("k7/8/8/8/8/7K/4p3/8").get
-    val engine = new GameEngine(initialBoard = board, initialTurn = Color.Black)
+    val engine = engineWith(board, Color.Black)
     val events = captureEvents(engine)
 
     engine.processUserInput("e2e1")
@@ -148,20 +144,3 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
     events.filter(_.isInstanceOf[MoveExecutedEvent]) should not be empty
     events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (false)
   }
-
-  test("completePromotion catch-all fires InvalidMoveEvent for unexpected MoveResult") {
-    // Inject a function that returns an unexpected MoveResult to hit the catch-all case
-    val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val stubFn: (de.nowchess.api.board.Board, de.nowchess.chess.logic.GameHistory, Square, Square, PromotionPiece, Color) => de.nowchess.chess.controller.MoveResult =
-      (_, _, _, _, _, _) => de.nowchess.chess.controller.MoveResult.NoPiece
-    val engine = new GameEngine(initialBoard = promotionBoard, completePromotionFn = stubFn)
-    val events = captureEvents(engine)
-
-    engine.processUserInput("e7e8")
-    engine.isPendingPromotion should be (true)
-
-    engine.completePromotion(PromotionPiece.Queen)
-
-    engine.isPendingPromotion should be (false)
-    events.exists(_.isInstanceOf[InvalidMoveEvent]) should be (true)
-  }
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineTest.scala
index 2712195..3138f35 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineTest.scala
@@ -2,7 +2,7 @@ package de.nowchess.chess.engine
 
 import scala.collection.mutable
 import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.game.GameContext
 import de.nowchess.chess.observer.{Observer, GameEvent, MoveExecutedEvent, CheckDetectedEvent, BoardResetEvent, InvalidMoveEvent, FiftyMoveRuleAvailableEvent, DrawClaimedEvent, MoveUndoneEvent, MoveRedoneEvent}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
@@ -12,7 +12,7 @@ class GameEngineTest extends AnyFunSuite with Matchers:
   test("GameEngine starts with initial board state"):
     val engine = new GameEngine()
     engine.board shouldBe Board.initial
-    engine.history shouldBe GameHistory.empty
+    engine.context.moves shouldBe empty
     engine.turn shouldBe Color.White
 
   test("GameEngine accepts Observer subscription"):
@@ -112,7 +112,6 @@ class GameEngineTest extends AnyFunSuite with Matchers:
   test("GameEngine undo restores previous state"):
     val engine = new GameEngine()
     engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
     engine.undo()
     engine.board shouldBe Board.initial
     engine.turn shouldBe Color.White
@@ -175,7 +174,6 @@ class GameEngineTest extends AnyFunSuite with Matchers:
   test("GameEngine undo via processUserInput"):
     val engine = new GameEngine()
     engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
     engine.processUserInput("undo")
     engine.board shouldBe Board.initial
 
@@ -200,15 +198,11 @@ class GameEngineTest extends AnyFunSuite with Matchers:
     engine.processUserInput("e2e4")
     engine.processUserInput("e7e5")
     engine.processUserInput("g1f3")
-    
     engine.turn shouldBe Color.Black
-    
     engine.undo()
     engine.turn shouldBe Color.White
-    
     engine.undo()
     engine.turn shouldBe Color.Black
-    
     engine.undo()
     engine.turn shouldBe Color.White
     engine.board shouldBe Board.initial
@@ -218,17 +212,13 @@ class GameEngineTest extends AnyFunSuite with Matchers:
     engine.processUserInput("e2e4")
     engine.processUserInput("e7e5")
     engine.processUserInput("g1f3")
-    
     engine.undo()
     engine.undo()
     engine.undo()
-    
     engine.redo()
     engine.turn shouldBe Color.Black
-    
     engine.redo()
     engine.turn shouldBe Color.White
-    
     engine.redo()
     engine.turn shouldBe Color.Black
 
@@ -238,17 +228,14 @@ class GameEngineTest extends AnyFunSuite with Matchers:
     engine.processUserInput("e7e5")
     engine.undo()
     engine.canRedo shouldBe true
-    
-    engine.processUserInput("e7e6")  // Different move
+    engine.processUserInput("e7e6")
     engine.canRedo shouldBe false
 
   test("GameEngine command history tracking"):
     val engine = new GameEngine()
     engine.commandHistory.size shouldBe 0
-    
     engine.processUserInput("e2e4")
     engine.commandHistory.size shouldBe 1
-    
     engine.processUserInput("e7e5")
     engine.commandHistory.size shouldBe 2
 
@@ -258,7 +245,6 @@ class GameEngineTest extends AnyFunSuite with Matchers:
     engine.subscribe(observer)
     val initialEvents = observer.events.size
     engine.processUserInput("quit")
-    // quit should not produce an event
     observer.events.size shouldBe initialEvents
 
   test("GameEngine quit via q"):
@@ -268,7 +254,7 @@ class GameEngineTest extends AnyFunSuite with Matchers:
     val initialEvents = observer.events.size
     engine.processUserInput("q")
     observer.events.size shouldBe initialEvents
-  
+
   test("GameEngine undo notifies with MoveUndoneEvent after successful undo"):
     val engine = new GameEngine()
     engine.processUserInput("e2e4")
@@ -276,10 +262,7 @@ class GameEngineTest extends AnyFunSuite with Matchers:
     val observer = new MockObserver()
     engine.subscribe(observer)
     observer.events.clear()
-
     engine.undo()
-
-    // Should have received a MoveUndoneEvent on undo
     observer.events.size should be > 0
     observer.events.exists(_.isInstanceOf[MoveUndoneEvent]) shouldBe true
 
@@ -288,22 +271,16 @@ class GameEngineTest extends AnyFunSuite with Matchers:
     engine.processUserInput("e2e4")
     engine.processUserInput("e7e5")
     val boardAfterSecondMove = engine.board
-
     engine.undo()
     val observer = new MockObserver()
     engine.subscribe(observer)
     observer.events.clear()
-
     engine.redo()
-
-    // Should have received a MoveRedoneEvent for the redo
     observer.events.size shouldBe 1
     observer.events.head shouldBe a[MoveRedoneEvent]
     engine.board shouldBe boardAfterSecondMove
     engine.turn shouldBe Color.White
 
-  // ──── 50-move rule ───────────────────────────────────────────────────
-
   test("GameEngine: 'draw' rejected when halfMoveClock < 100"):
     val engine = new GameEngine()
     val observer = new MockObserver()
@@ -313,7 +290,7 @@ class GameEngineTest extends AnyFunSuite with Matchers:
     observer.events.head shouldBe a[InvalidMoveEvent]
 
   test("GameEngine: 'draw' accepted and fires DrawClaimedEvent when halfMoveClock >= 100"):
-    val engine = new GameEngine(initialHistory = GameHistory(halfMoveClock = 100))
+    val engine = new GameEngine(initialContext = GameContext.initial.withHalfMoveClock(100))
     val observer = new MockObserver()
     engine.subscribe(observer)
     engine.processUserInput("draw")
@@ -321,31 +298,27 @@ class GameEngineTest extends AnyFunSuite with Matchers:
     observer.events.head shouldBe a[DrawClaimedEvent]
 
   test("GameEngine: state resets to initial after draw claimed"):
-    val engine = new GameEngine(initialHistory = GameHistory(halfMoveClock = 100))
+    val engine = new GameEngine(initialContext = GameContext.initial.withHalfMoveClock(100))
     engine.processUserInput("draw")
     engine.board shouldBe Board.initial
-    engine.history shouldBe GameHistory.empty
+    engine.context.moves shouldBe empty
     engine.turn shouldBe Color.White
 
   test("GameEngine: FiftyMoveRuleAvailableEvent fired when move brings clock to 100"):
-    // Start at clock 99; a knight move (non-pawn, non-capture) increments to 100
-    val engine = new GameEngine(initialHistory = GameHistory(halfMoveClock = 99))
+    val engine = new GameEngine(initialContext = GameContext.initial.withHalfMoveClock(99))
     val observer = new MockObserver()
     engine.subscribe(observer)
-    engine.processUserInput("g1f3")  // knight move on initial board
-    // Should receive MoveExecutedEvent AND FiftyMoveRuleAvailableEvent
+    engine.processUserInput("g1f3")
     observer.events.exists(_.isInstanceOf[FiftyMoveRuleAvailableEvent]) shouldBe true
 
   test("GameEngine: FiftyMoveRuleAvailableEvent not fired when clock is below 100 after move"):
-    val engine = new GameEngine(initialHistory = GameHistory(halfMoveClock = 5))
+    val engine = new GameEngine(initialContext = GameContext.initial.withHalfMoveClock(5))
     val observer = new MockObserver()
     engine.subscribe(observer)
     engine.processUserInput("g1f3")
     observer.events.exists(_.isInstanceOf[FiftyMoveRuleAvailableEvent]) shouldBe false
 
-  // Mock Observer for testing
   private class MockObserver extends Observer:
     val events = mutable.ListBuffer[GameEvent]()
     override def onGameEvent(event: GameEvent): Unit =
       events += event
-
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/MoveCommandDefaultsTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/MoveCommandDefaultsTest.scala
deleted file mode 100644
index 46df874..0000000
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/MoveCommandDefaultsTest.scala
+++ /dev/null
@@ -1,110 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class MoveCommandDefaultsTest extends AnyFunSuite with Matchers:
-  
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  // Tests for MoveCommand with default parameter values
-  test("MoveCommand with no moveResult defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.moveResult shouldBe None
-    cmd.execute() shouldBe false
-
-  test("MoveCommand with no previousBoard defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.previousBoard shouldBe None
-    cmd.undo() shouldBe false
-
-  test("MoveCommand with no previousHistory defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.previousHistory shouldBe None
-    cmd.undo() shouldBe false
-
-  test("MoveCommand with no previousTurn defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.previousTurn shouldBe None
-    cmd.undo() shouldBe false
-
-  test("MoveCommand description is always returned"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.description shouldBe "Move from e2 to e4"
-
-  test("MoveCommand execute returns false when moveResult is None"):
-    val cmd = MoveCommand(
-      from = sq(File.A, Rank.R1),
-      to = sq(File.B, Rank.R3)
-    )
-    cmd.execute() shouldBe false
-
-  test("MoveCommand undo returns false when any previous state is None"):
-    // Missing previousBoard
-    val cmd1 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = None,
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-    cmd1.undo() shouldBe false
-
-    // Missing previousHistory
-    val cmd2 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = None,
-      previousTurn = Some(Color.White)
-    )
-    cmd2.undo() shouldBe false
-
-    // Missing previousTurn
-    val cmd3 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = None
-    )
-    cmd3.undo() shouldBe false
-
-  test("MoveCommand execute returns true when moveResult is defined"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None))
-    )
-    cmd.execute() shouldBe true
-
-  test("MoveCommand undo returns true when all previous states are defined"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-    cmd.undo() shouldBe true
diff --git a/modules/core/src/test/scala/de/nowchess/chess/logic/CastlingRightsCalculatorTest.scala b/modules/core/src/test/scala/de/nowchess/chess/logic/CastlingRightsCalculatorTest.scala
deleted file mode 100644
index d9f3e20..0000000
--- a/modules/core/src/test/scala/de/nowchess/chess/logic/CastlingRightsCalculatorTest.scala
+++ /dev/null
@@ -1,70 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.CastlingRights
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class CastlingRightsCalculatorTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  test("Empty history gives full castling rights"):
-    val rights = CastlingRightsCalculator.deriveCastlingRights(GameHistory.empty, Color.White)
-    rights shouldBe CastlingRights.Both
-
-  test("White loses kingside rights after h1 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.H, Rank.R1), sq(File.H, Rank.R2))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights.kingSide shouldBe false
-    rights.queenSide shouldBe true
-
-  test("White loses queenside rights after a1 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.A, Rank.R1), sq(File.A, Rank.R2))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights.queenSide shouldBe false
-    rights.kingSide shouldBe true
-
-  test("White loses all rights after king moves"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R1), sq(File.E, Rank.R2))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights shouldBe CastlingRights.None
-
-  test("Black loses kingside rights after h8 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.H, Rank.R8), sq(File.H, Rank.R7))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.Black)
-    rights.kingSide shouldBe false
-    rights.queenSide shouldBe true
-
-  test("Black loses queenside rights after a8 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.A, Rank.R8), sq(File.A, Rank.R7))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.Black)
-    rights.queenSide shouldBe false
-    rights.kingSide shouldBe true
-
-  test("Black loses all rights after king moves"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R8), sq(File.E, Rank.R7))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.Black)
-    rights shouldBe CastlingRights.None
-
-  test("Castle move revokes all castling rights"):
-    val history = GameHistory.empty.addMove(
-      sq(File.E, Rank.R1),
-      sq(File.G, Rank.R1),
-      Some(CastleSide.Kingside)
-    )
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights shouldBe CastlingRights.None
-
-  test("Other pieces moving does not revoke castling rights"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights shouldBe CastlingRights.Both
-
-  test("Multiple moves preserve white kingside but lose queenside"):
-    val history = GameHistory.empty
-      .addMove(sq(File.A, Rank.R1), sq(File.A, Rank.R2))  // White queenside rook moves
-      .addMove(sq(File.E, Rank.R7), sq(File.E, Rank.R5))  // Black pawn moves
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights.kingSide shouldBe true
-    rights.queenSide shouldBe false
diff --git a/modules/core/src/test/scala/de/nowchess/chess/logic/EnPassantCalculatorTest.scala b/modules/core/src/test/scala/de/nowchess/chess/logic/EnPassantCalculatorTest.scala
deleted file mode 100644
index 31963f5..0000000
--- a/modules/core/src/test/scala/de/nowchess/chess/logic/EnPassantCalculatorTest.scala
+++ /dev/null
@@ -1,101 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class EnPassantCalculatorTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-  private def board(entries: (Square, Piece)*): Board = Board(entries.toMap)
-
-  // ──── enPassantTarget ────────────────────────────────────────────────
-
-  test("enPassantTarget returns None for empty history"):
-    val b = board(sq(File.E, Rank.R4) -> Piece.WhitePawn)
-    EnPassantCalculator.enPassantTarget(b, GameHistory.empty) shouldBe None
-
-  test("enPassantTarget returns None when last move was a single pawn push"):
-    val b = board(sq(File.E, Rank.R3) -> Piece.WhitePawn)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R3))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe None
-
-  test("enPassantTarget returns None when last move was not a pawn"):
-    val b = board(sq(File.E, Rank.R4) -> Piece.WhiteRook)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe None
-
-  test("enPassantTarget returns e3 after white pawn double push e2-e4"):
-    val b = board(sq(File.E, Rank.R4) -> Piece.WhitePawn)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe Some(sq(File.E, Rank.R3))
-
-  test("enPassantTarget returns e6 after black pawn double push e7-e5"):
-    val b = board(sq(File.E, Rank.R5) -> Piece.BlackPawn)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe Some(sq(File.E, Rank.R6))
-
-  test("enPassantTarget returns d3 after white pawn double push d2-d4"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhitePawn)
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe Some(sq(File.D, Rank.R3))
-
-  // ──── capturedPawnSquare ─────────────────────────────────────────────
-
-  test("capturedPawnSquare for white capturing on e6 returns e5"):
-    EnPassantCalculator.capturedPawnSquare(sq(File.E, Rank.R6), Color.White) shouldBe sq(File.E, Rank.R5)
-
-  test("capturedPawnSquare for black capturing on e3 returns e4"):
-    EnPassantCalculator.capturedPawnSquare(sq(File.E, Rank.R3), Color.Black) shouldBe sq(File.E, Rank.R4)
-
-  test("capturedPawnSquare for white capturing on d6 returns d5"):
-    EnPassantCalculator.capturedPawnSquare(sq(File.D, Rank.R6), Color.White) shouldBe sq(File.D, Rank.R5)
-
-  // ──── isEnPassant ────────────────────────────────────────────────────
-
-  test("isEnPassant returns true for valid white en passant capture"):
-    // White pawn on e5, black pawn just double-pushed to d5 (ep target = d6)
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe true
-
-  test("isEnPassant returns true for valid black en passant capture"):
-    // Black pawn on d4, white pawn just double-pushed to e4 (ep target = e3)
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.BlackPawn,
-      sq(File.E, Rank.R4) -> Piece.WhitePawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.D, Rank.R4), sq(File.E, Rank.R3)) shouldBe true
-
-  test("isEnPassant returns false when no en passant target in history"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R6), sq(File.D, Rank.R5))  // single push
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe false
-
-  test("isEnPassant returns false when piece at from is not a pawn"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhiteRook,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe false
-
-  test("isEnPassant returns false when to does not match ep target"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.E, Rank.R6)) shouldBe false
-
-  test("isEnPassant returns false when from square is empty"):
-    val b = board(sq(File.D, Rank.R5) -> Piece.BlackPawn)
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe false
diff --git a/modules/core/src/test/scala/de/nowchess/chess/logic/GameHistoryTest.scala b/modules/core/src/test/scala/de/nowchess/chess/logic/GameHistoryTest.scala
index 8a6069f..919b736 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/logic/GameHistoryTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/logic/GameHistoryTest.scala
@@ -2,6 +2,7 @@ package de.nowchess.chess.logic
 
 import de.nowchess.api.board.*
 import de.nowchess.api.move.PromotionPiece
+import de.nowchess.api.game.{GameHistory, HistoryMove}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -32,9 +33,9 @@ class GameHistoryTest extends AnyFunSuite with Matchers:
     val history = GameHistory.empty.addMove(
       sq(File.E, Rank.R1),
       sq(File.G, Rank.R1),
-      Some(CastleSide.Kingside)
+      Some("Kingside")
     )
-    history.moves.head.castleSide shouldBe Some(CastleSide.Kingside)
+    history.moves.head.castleSide shouldBe Some("Kingside")
 
   test("GameHistory.addMove with two arguments uses None for castleSide default"):
     val history = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
@@ -58,9 +59,9 @@ class GameHistoryTest extends AnyFunSuite with Matchers:
   test("addMove with castleSide only uses promotionPiece default (None)"):
     val history = GameHistory.empty
     // With overload 3 removed, this uses the 4-param version and triggers addMove$default$4
-    val newHistory = history.addMove(sq(File.E, Rank.R1), sq(File.G, Rank.R1), Some(CastleSide.Kingside))
+    val newHistory = history.addMove(sq(File.E, Rank.R1), sq(File.G, Rank.R1), Some("Kingside"))
     newHistory.moves should have length 1
-    newHistory.moves.head.castleSide should be (Some(CastleSide.Kingside))
+    newHistory.moves.head.castleSide should be (Some("Kingside"))
     newHistory.moves.head.promotionPiece should be (None)
 
   test("addMove using named parameters with only promotion, using castleSide default"):
diff --git a/modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala b/modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala
deleted file mode 100644
index 5f02f19..0000000
--- a/modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala
+++ /dev/null
@@ -1,161 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.CastlingRights
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameRulesTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-  private def board(entries: (Square, Piece)*): Board = Board(entries.toMap)
-
-  /** Wrap a board in a GameContext with no castling rights — for non-castling tests. */
-  private def testLegalMoves(entries: (Square, Piece)*)(color: Color): Set[(Square, Square)] =
-    GameRules.legalMoves(Board(entries.toMap), GameHistory.empty, color)
-
-  private def testGameStatus(entries: (Square, Piece)*)(color: Color): PositionStatus =
-    GameRules.gameStatus(Board(entries.toMap), GameHistory.empty, color)
-
-  // ──── isInCheck ──────────────────────────────────────────────────────
-
-  test("isInCheck: king attacked by enemy rook on same rank"):
-    // White King E1, Black Rook A1 — rook slides along rank 1 to E1
-    val b = board(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R1) -> Piece.BlackRook
-    )
-    GameRules.isInCheck(b, Color.White) shouldBe true
-
-  test("isInCheck: king not attacked"):
-    // Black Rook A3 does not cover E1
-    val b = board(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R3) -> Piece.BlackRook
-    )
-    GameRules.isInCheck(b, Color.White) shouldBe false
-
-  test("isInCheck: no king on board returns false"):
-    val b = board(sq(File.A, Rank.R1) -> Piece.BlackRook)
-    GameRules.isInCheck(b, Color.White) shouldBe false
-
-  // ──── legalMoves ─────────────────────────────────────────────────────
-
-  test("legalMoves: move that exposes own king to rook is excluded"):
-    // White King E1, White Rook E4 (pinned on E-file), Black Rook E8
-    // Moving the White Rook off the E-file would expose the king
-    val moves = testLegalMoves(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.E, Rank.R4) -> Piece.WhiteRook,
-      sq(File.E, Rank.R8) -> Piece.BlackRook
-    )(Color.White)
-    moves should not contain (sq(File.E, Rank.R4) -> sq(File.D, Rank.R4))
-
-  test("legalMoves: move that blocks check is included"):
-    // White King E1 in check from Black Rook E8; White Rook A5 can interpose on E5
-    val moves = testLegalMoves(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R5) -> Piece.WhiteRook,
-      sq(File.E, Rank.R8) -> Piece.BlackRook
-    )(Color.White)
-    moves should contain(sq(File.A, Rank.R5) -> sq(File.E, Rank.R5))
-
-  // ──── gameStatus ──────────────────────────────────────────────────────
-
-  test("gameStatus: checkmate returns Mated"):
-    // White Qh8, Ka6; Black Ka8
-    // Qh8 attacks Ka8 along rank 8; all escape squares covered (spec-verified position)
-    testGameStatus(
-      sq(File.H, Rank.R8) -> Piece.WhiteQueen,
-      sq(File.A, Rank.R6) -> Piece.WhiteKing,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    )(Color.Black) shouldBe PositionStatus.Mated
-
-  test("gameStatus: stalemate returns Drawn"):
-    // White Qb6, Kc6; Black Ka8
-    // Black king has no legal moves and is not in check (spec-verified position)
-    testGameStatus(
-      sq(File.B, Rank.R6) -> Piece.WhiteQueen,
-      sq(File.C, Rank.R6) -> Piece.WhiteKing,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    )(Color.Black) shouldBe PositionStatus.Drawn
-
-  test("gameStatus: king in check with legal escape returns InCheck"):
-    // White Ra8 attacks Black Ke8 along rank 8; king can escape to d7, e7, f7
-    testGameStatus(
-      sq(File.A, Rank.R8) -> Piece.WhiteRook,
-      sq(File.E, Rank.R8) -> Piece.BlackKing
-    )(Color.Black) shouldBe PositionStatus.InCheck
-
-  test("gameStatus: normal starting position returns Normal"):
-    GameRules.gameStatus(Board.initial, GameHistory.empty, Color.White) shouldBe PositionStatus.Normal
-
-  test("legalMoves: includes castling destination when available"):
-    val b = board(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.H, Rank.R8) -> Piece.BlackKing
-      )
-    GameRules.legalMoves(b, GameHistory.empty, Color.White) should contain(sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
-
-  test("legalMoves: excludes castling when king is in check"):
-    val b = board(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.E, Rank.R8) -> Piece.BlackRook,
-        sq(File.A, Rank.R8) -> Piece.BlackKing
-      )
-    GameRules.legalMoves(b, GameHistory.empty, Color.White) should not contain (sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
-
-  test("gameStatus: returns Normal (not Drawn) when castling is the only legal move"):
-    // White King e1, Rook h1 (kingside castling available).
-    // Black Rooks d2 and f2 box the king: d1 attacked by d2, e2 attacked by both,
-    // f1 attacked by f2. King cannot move to any adjacent square without entering
-    // an attacked square or an enemy piece. Only legal move: castle to g1.
-    val b = board(
-        sq(File.E, Rank.R1) -> Piece.WhiteKing,
-        sq(File.H, Rank.R1) -> Piece.WhiteRook,
-        sq(File.D, Rank.R2) -> Piece.BlackRook,
-        sq(File.F, Rank.R2) -> Piece.BlackRook,
-        sq(File.A, Rank.R8) -> Piece.BlackKing
-      )
-    // No history means castling rights are intact
-    GameRules.gameStatus(b, GameHistory.empty, Color.White) shouldBe PositionStatus.Normal
-
-  test("CastleSide.withCastle correctly positions pieces for Queenside castling"):
-    // Directly test the withCastle extension for Queenside (coverage gap on line 10)
-    val b = board(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R1) -> Piece.WhiteRook,
-      sq(File.H, Rank.R8) -> Piece.BlackKing
-    )
-    val result = b.withCastle(Color.White, CastleSide.Queenside)
-    result.pieceAt(sq(File.C, Rank.R1)) shouldBe Some(Piece.WhiteKing)
-    result.pieceAt(sq(File.D, Rank.R1)) shouldBe Some(Piece.WhiteRook)
-    result.pieceAt(sq(File.E, Rank.R1)) shouldBe None
-    result.pieceAt(sq(File.A, Rank.R1)) shouldBe None
-
-  test("CastleSide.withCastle correctly positions pieces for Black Kingside castling"):
-    val b = board(
-      sq(File.E, Rank.R8) -> Piece.BlackKing,
-      sq(File.H, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R1) -> Piece.WhiteKing
-    )
-    val result = b.withCastle(Color.Black, CastleSide.Kingside)
-    result.pieceAt(sq(File.G, Rank.R8)) shouldBe Some(Piece.BlackKing)
-    result.pieceAt(sq(File.F, Rank.R8)) shouldBe Some(Piece.BlackRook)
-    result.pieceAt(sq(File.E, Rank.R8)) shouldBe None
-    result.pieceAt(sq(File.H, Rank.R8)) shouldBe None
-
-  test("CastleSide.withCastle correctly positions pieces for Black Queenside castling"):
-    val b = board(
-      sq(File.E, Rank.R8) -> Piece.BlackKing,
-      sq(File.A, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R1) -> Piece.WhiteKing
-    )
-    val result = b.withCastle(Color.Black, CastleSide.Queenside)
-    result.pieceAt(sq(File.C, Rank.R8)) shouldBe Some(Piece.BlackKing)
-    result.pieceAt(sq(File.D, Rank.R8)) shouldBe Some(Piece.BlackRook)
-    result.pieceAt(sq(File.E, Rank.R8)) shouldBe None
-    result.pieceAt(sq(File.A, Rank.R8)) shouldBe None
diff --git a/modules/core/src/test/scala/de/nowchess/chess/logic/MoveValidatorTest.scala b/modules/core/src/test/scala/de/nowchess/chess/logic/MoveValidatorTest.scala
deleted file mode 100644
index b5dce75..0000000
--- a/modules/core/src/test/scala/de/nowchess/chess/logic/MoveValidatorTest.scala
+++ /dev/null
@@ -1,280 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.{Board, Color, File, Piece, Rank, Square}
-import de.nowchess.api.game.CastlingRights
-import de.nowchess.chess.logic.{CastleSide, GameHistory}
-import de.nowchess.chess.notation.FenParser
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class MoveValidatorTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-  private def board(entries: (Square, Piece)*): Board = Board(entries.toMap)
-
-  // ──── Empty square ───────────────────────────────────────────────────
-
-  test("legalTargets returns empty set when no piece at from square"):
-    MoveValidator.legalTargets(Board.initial, sq(File.E, Rank.R4)) shouldBe empty
-
-  // ──── isLegal delegates to legalTargets ──────────────────────────────
-
-  test("isLegal returns true for a valid pawn move"):
-    MoveValidator.isLegal(Board.initial, sq(File.E, Rank.R2), sq(File.E, Rank.R4)) shouldBe true
-
-  test("isLegal returns false for an invalid move"):
-    MoveValidator.isLegal(Board.initial, sq(File.E, Rank.R2), sq(File.E, Rank.R5)) shouldBe false
-
-  // ──── Pawn – White ───────────────────────────────────────────────────
-
-  test("white pawn on starting rank can move forward one square"):
-    val b = board(sq(File.E, Rank.R2) -> Piece.WhitePawn)
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R2)) should contain(sq(File.E, Rank.R3))
-
-  test("white pawn on starting rank can move forward two squares"):
-    val b = board(sq(File.E, Rank.R2) -> Piece.WhitePawn)
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R2)) should contain(sq(File.E, Rank.R4))
-
-  test("white pawn not on starting rank cannot move two squares"):
-    val b = board(sq(File.E, Rank.R3) -> Piece.WhitePawn)
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R3)) should not contain sq(File.E, Rank.R5)
-
-  test("white pawn is blocked by piece directly in front, and cannot jump over it"):
-    val b = board(
-      sq(File.E, Rank.R2) -> Piece.WhitePawn,
-      sq(File.E, Rank.R3) -> Piece.BlackPawn
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.E, Rank.R2))
-    targets should not contain sq(File.E, Rank.R3)
-    targets should not contain sq(File.E, Rank.R4)
-
-  test("white pawn on starting rank cannot move two squares if destination square is occupied"):
-    val b = board(
-      sq(File.E, Rank.R2) -> Piece.WhitePawn,
-      sq(File.E, Rank.R4) -> Piece.BlackPawn
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.E, Rank.R2))
-    targets should contain(sq(File.E, Rank.R3))
-    targets should not contain sq(File.E, Rank.R4)
-
-  test("white pawn can capture diagonally when enemy piece is present"):
-    val b = board(
-      sq(File.E, Rank.R2) -> Piece.WhitePawn,
-      sq(File.D, Rank.R3) -> Piece.BlackPawn
-    )
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R2)) should contain(sq(File.D, Rank.R3))
-
-  test("white pawn cannot capture diagonally when no enemy piece is present"):
-    val b = board(sq(File.E, Rank.R2) -> Piece.WhitePawn)
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R2)) should not contain sq(File.D, Rank.R3)
-
-  test("white pawn at A-file does not generate diagonal to the left off the board"):
-    val b = board(sq(File.A, Rank.R2) -> Piece.WhitePawn)
-    val targets = MoveValidator.legalTargets(b, sq(File.A, Rank.R2))
-    targets should contain(sq(File.A, Rank.R3))
-    targets should contain(sq(File.A, Rank.R4))
-    targets.size shouldBe 2
-
-  // ──── Pawn – Black ───────────────────────────────────────────────────
-
-  test("black pawn on starting rank can move forward one and two squares"):
-    val b = board(sq(File.E, Rank.R7) -> Piece.BlackPawn)
-    val targets = MoveValidator.legalTargets(b, sq(File.E, Rank.R7))
-    targets should contain(sq(File.E, Rank.R6))
-    targets should contain(sq(File.E, Rank.R5))
-
-  test("black pawn not on starting rank cannot move two squares"):
-    val b = board(sq(File.E, Rank.R6) -> Piece.BlackPawn)
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R6)) should not contain sq(File.E, Rank.R4)
-
-  test("black pawn can capture diagonally when enemy piece is present"):
-    val b = board(
-      sq(File.E, Rank.R7) -> Piece.BlackPawn,
-      sq(File.F, Rank.R6) -> Piece.WhitePawn
-    )
-    MoveValidator.legalTargets(b, sq(File.E, Rank.R7)) should contain(sq(File.F, Rank.R6))
-
-  // ──── Knight ─────────────────────────────────────────────────────────
-
-  test("knight in center has 8 possible moves"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteKnight)
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)).size shouldBe 8
-
-  test("knight in corner has only 2 possible moves"):
-    val b = board(sq(File.A, Rank.R1) -> Piece.WhiteKnight)
-    MoveValidator.legalTargets(b, sq(File.A, Rank.R1)).size shouldBe 2
-
-  test("knight cannot land on own piece"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteKnight,
-      sq(File.F, Rank.R5) -> Piece.WhiteRook
-    )
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should not contain sq(File.F, Rank.R5)
-
-  test("knight can capture enemy piece"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteKnight,
-      sq(File.F, Rank.R5) -> Piece.BlackRook
-    )
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should contain(sq(File.F, Rank.R5))
-
-  // ──── Bishop ─────────────────────────────────────────────────────────
-
-  test("bishop slides diagonally across an empty board"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteBishop)
-    val targets = MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-    targets should contain(sq(File.E, Rank.R5))
-    targets should contain(sq(File.H, Rank.R8))
-    targets should contain(sq(File.C, Rank.R3))
-    targets should contain(sq(File.A, Rank.R1))
-
-  test("bishop is blocked by own piece and squares beyond are unreachable"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteBishop,
-      sq(File.F, Rank.R6) -> Piece.WhiteRook
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-    targets should contain(sq(File.E, Rank.R5))
-    targets should not contain sq(File.F, Rank.R6)
-    targets should not contain sq(File.G, Rank.R7)
-
-  test("bishop captures enemy piece and cannot slide further"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteBishop,
-      sq(File.F, Rank.R6) -> Piece.BlackRook
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-    targets should contain(sq(File.E, Rank.R5))
-    targets should contain(sq(File.F, Rank.R6))
-    targets should not contain sq(File.G, Rank.R7)
-
-  // ──── Rook ───────────────────────────────────────────────────────────
-
-  test("rook slides orthogonally across an empty board"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteRook)
-    val targets = MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-    targets should contain(sq(File.D, Rank.R8))
-    targets should contain(sq(File.D, Rank.R1))
-    targets should contain(sq(File.A, Rank.R4))
-    targets should contain(sq(File.H, Rank.R4))
-
-  test("rook is blocked by own piece and squares beyond are unreachable"):
-    val b = board(
-      sq(File.A, Rank.R1) -> Piece.WhiteRook,
-      sq(File.C, Rank.R1) -> Piece.WhitePawn
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.A, Rank.R1))
-    targets should contain(sq(File.B, Rank.R1))
-    targets should not contain sq(File.C, Rank.R1)
-    targets should not contain sq(File.D, Rank.R1)
-
-  test("rook captures enemy piece and cannot slide further"):
-    val b = board(
-      sq(File.A, Rank.R1) -> Piece.WhiteRook,
-      sq(File.C, Rank.R1) -> Piece.BlackPawn
-    )
-    val targets = MoveValidator.legalTargets(b, sq(File.A, Rank.R1))
-    targets should contain(sq(File.B, Rank.R1))
-    targets should contain(sq(File.C, Rank.R1))
-    targets should not contain sq(File.D, Rank.R1)
-
-  // ──── Queen ──────────────────────────────────────────────────────────
-
-  test("queen combines rook and bishop movement for 27 squares from d4"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteQueen)
-    val targets = MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-    targets should contain(sq(File.D, Rank.R8))
-    targets should contain(sq(File.H, Rank.R4))
-    targets should contain(sq(File.H, Rank.R8))
-    targets should contain(sq(File.A, Rank.R1))
-    targets.size shouldBe 27
-
-  // ──── King ───────────────────────────────────────────────────────────
-
-  test("king moves one step in all 8 directions from center"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteKing)
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)).size shouldBe 8
-
-  test("king at corner has only 3 reachable squares"):
-    val b = board(sq(File.A, Rank.R1) -> Piece.WhiteKing)
-    MoveValidator.legalTargets(b, sq(File.A, Rank.R1)).size shouldBe 3
-
-  test("king cannot capture own piece"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteKing,
-      sq(File.E, Rank.R4) -> Piece.WhiteRook
-    )
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should not contain sq(File.E, Rank.R4)
-
-  test("king can capture enemy piece"):
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.WhiteKing,
-      sq(File.E, Rank.R4) -> Piece.BlackRook
-    )
-    MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should contain(sq(File.E, Rank.R4))
-
-  // ──── Pawn – en passant targets ──────────────────────────────────────
-
-  test("white pawn includes ep target in legal moves after black double push"):
-    // Black pawn just double-pushed to d5 (ep target = d6); white pawn on e5
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    MoveValidator.legalTargets(b, h, sq(File.E, Rank.R5)) should contain(sq(File.D, Rank.R6))
-
-  test("white pawn does not include ep target without a preceding double push"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R6), sq(File.D, Rank.R5))  // single push
-    MoveValidator.legalTargets(b, h, sq(File.E, Rank.R5)) should not contain sq(File.D, Rank.R6)
-
-  test("black pawn includes ep target in legal moves after white double push"):
-    // White pawn just double-pushed to e4 (ep target = e3); black pawn on d4
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.BlackPawn,
-      sq(File.E, Rank.R4) -> Piece.WhitePawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    MoveValidator.legalTargets(b, h, sq(File.D, Rank.R4)) should contain(sq(File.E, Rank.R3))
-
-  test("pawn on wrong file does not get ep target from adjacent double push"):
-    // White pawn on a5, black pawn double-pushed to d5 — a5 is not adjacent to d5
-    val b = board(
-      sq(File.A, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    MoveValidator.legalTargets(b, h, sq(File.A, Rank.R5)) should not contain sq(File.D, Rank.R6)
-
-  // ──── History-aware legalTargets fallback for non-pawn non-king pieces ─────
-
-  test("legalTargets with history delegates to geometry-only for non-pawn non-king pieces"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteRook)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    MoveValidator.legalTargets(b, h, sq(File.D, Rank.R4)) shouldBe MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
-
-  // ──── isPromotionMove ────────────────────────────────────────────────
-
-  test("White pawn reaching R8 is a promotion move"):
-    val b = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R7), Square(File.E, Rank.R8)) should be (true)
-
-  test("Black pawn reaching R1 is a promotion move"):
-    val b = FenParser.parseBoard("8/8/8/8/4K3/8/4p3/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R2), Square(File.E, Rank.R1)) should be (true)
-
-  test("Pawn capturing to back rank is a promotion move"):
-    val b = FenParser.parseBoard("3q4/4P3/8/8/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R7), Square(File.D, Rank.R8)) should be (true)
-
-  test("Pawn not reaching back rank is not a promotion move"):
-    val b = FenParser.parseBoard("8/8/8/4P3/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R5), Square(File.E, Rank.R6)) should be (false)
-
-  test("Non-pawn piece is never a promotion move"):
-    val b = FenParser.parseBoard("8/8/8/4Q3/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R5), Square(File.E, Rank.R8)) should be (false)
diff --git a/modules/core/src/test/scala/de/nowchess/chess/notation/FenExporterTest.scala b/modules/core/src/test/scala/de/nowchess/chess/notation/FenExporterTest.scala
index 6734b15..7b4d11a 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/notation/FenExporterTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/notation/FenExporterTest.scala
@@ -1,7 +1,8 @@
 package de.nowchess.chess.notation
 
 import de.nowchess.api.board.*
-import de.nowchess.api.game.*
+import de.nowchess.api.game.{CastlingRights, GameState, GameStatus}
+import de.nowchess.api.board.Color
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -69,7 +70,7 @@ class FenExporterTest extends AnyFunSuite with Matchers:
     fen shouldBe "rnbqkbnr/pp1ppppp/8/2pP4/8/8/PPPP1PPP/RNBQKBNR w KQkq c6 2 3"
 
   test("halfMoveClock round-trips through FEN export and import"):
-    import de.nowchess.chess.logic.GameHistory
+    import de.nowchess.api.game.GameHistory
     import de.nowchess.chess.notation.FenParser
     val history = GameHistory(halfMoveClock = 42)
     val gameState = GameState(
diff --git a/modules/core/src/test/scala/de/nowchess/chess/notation/PgnExporterTest.scala b/modules/core/src/test/scala/de/nowchess/chess/notation/PgnExporterTest.scala
index 7d453df..6a4f15a 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/notation/PgnExporterTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/notation/PgnExporterTest.scala
@@ -2,7 +2,7 @@ package de.nowchess.chess.notation
 
 import de.nowchess.api.board.{PieceType, *}
 import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{GameHistory, HistoryMove, CastleSide}
+import de.nowchess.api.game.{GameHistory, HistoryMove}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -30,7 +30,7 @@ class PgnExporterTest extends AnyFunSuite with Matchers:
   test("export castling") {
     val headers = Map("Event" -> "Test")
     val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R1), Square(File.G, Rank.R1), Some(CastleSide.Kingside)))
+      .addMove(HistoryMove(Square(File.E, Rank.R1), Square(File.G, Rank.R1), Some("Kingside")))
     val pgn = PgnExporter.exportGame(headers, history)
 
     pgn.contains("O-O") shouldBe true
@@ -59,7 +59,7 @@ class PgnExporterTest extends AnyFunSuite with Matchers:
   test("export queenside castling") {
     val headers = Map("Event" -> "Test")
     val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R1), Square(File.C, Rank.R1), Some(CastleSide.Queenside)))
+      .addMove(HistoryMove(Square(File.E, Rank.R1), Square(File.C, Rank.R1), Some("Queenside")))
     val pgn = PgnExporter.exportGame(headers, history)
 
     pgn.contains("O-O-O") shouldBe true
diff --git a/modules/core/src/test/scala/de/nowchess/chess/notation/PgnParserTest.scala b/modules/core/src/test/scala/de/nowchess/chess/notation/PgnParserTest.scala
index 520f842..7694a9d 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/notation/PgnParserTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/notation/PgnParserTest.scala
@@ -1,8 +1,8 @@
 package de.nowchess.chess.notation
 
 import de.nowchess.api.board.*
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{GameHistory, HistoryMove, CastleSide}
+import de.nowchess.api.move.{MoveType, PromotionPiece}
+import de.nowchess.api.game.GameContext
 import de.nowchess.chess.notation.FenParser
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
@@ -49,13 +49,13 @@ class PgnParserTest extends AnyFunSuite with Matchers:
 [White "A"]
 [Black "B"]
 
-1. e4 e5 2. Nxe5
+1. Nf3 e5 2. Nxe5
 """
     val game = PgnParser.parsePgn(pgn)
 
     game.isDefined shouldBe true
     game.get.moves.length shouldBe 3
-    // Nxe5: knight captures on e5
+    // Nxe5: knight on f3 captures pawn on e5
     game.get.moves(2).to shouldBe Square(File.E, Rank.R5)
   }
 
@@ -89,16 +89,16 @@ class PgnParserTest extends AnyFunSuite with Matchers:
   }
 
   test("parse PGN black kingside castling O-O") {
-    // After e4 e5 Nf3 Nc6 Bc4 Bc5, black can castle kingside
+    // After e4 e5 Nf3 Nf6 Bc4 Be7, both sides have cleared kingside for castling
     val pgn = """[Event "Test"]
 
-1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. O-O O-O
+1. e4 e5 2. Nf3 Nf6 3. Bc4 Be7 4. O-O O-O
 """
     val game = PgnParser.parsePgn(pgn)
 
     game.isDefined shouldBe true
     val blackCastle = game.get.moves.last
-    blackCastle.castleSide shouldBe Some(CastleSide.Kingside)
+    blackCastle.castleSide shouldBe Some("Kingside")
     blackCastle.from shouldBe Square(File.E, Rank.R8)
     blackCastle.to shouldBe Square(File.G, Rank.R8)
   }
@@ -117,28 +117,25 @@ class PgnParserTest extends AnyFunSuite with Matchers:
 
   test("parseAlgebraicMove: unrecognised token returns None and is skipped") {
     val board = Board.initial
-    val history = GameHistory.empty
     // "zzz" is not valid algebraic notation
-    val result = PgnParser.parseAlgebraicMove("zzz", board, history, Color.White)
+    val result = PgnParser.parseAlgebraicMove("zzz", GameContext.initial.withBoard(board), Color.White)
     result shouldBe None
   }
 
   test("parseAlgebraicMove: piece moves use charToPieceType for N B R Q K") {
     // Test that piece type characters are recognised
     val board = Board.initial
-    val history = GameHistory.empty
 
     // Nf3 - knight move
-    val nMove = PgnParser.parseAlgebraicMove("Nf3", board, history, Color.White)
+    val nMove = PgnParser.parseAlgebraicMove("Nf3", GameContext.initial.withBoard(board), Color.White)
     nMove.isDefined shouldBe true
     nMove.get.to shouldBe Square(File.F, Rank.R3)
   }
 
   test("parseAlgebraicMove: single char that is too short returns None") {
     val board = Board.initial
-    val history = GameHistory.empty
     // Single char that is not castling and cleaned length < 2
-    val result = PgnParser.parseAlgebraicMove("e", board, history, Color.White)
+    val result = PgnParser.parseAlgebraicMove("e", GameContext.initial.withBoard(board), Color.White)
     result shouldBe None
   }
 
@@ -153,9 +150,8 @@ class PgnParserTest extends AnyFunSuite with Matchers:
       Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
     )
     val board = Board(pieces)
-    val history = GameHistory.empty
 
-    val result = PgnParser.parseAlgebraicMove("Rad1", board, history, Color.White)
+    val result = PgnParser.parseAlgebraicMove("Rad1", GameContext.initial.withBoard(board), Color.White)
     result.isDefined shouldBe true
     result.get.from shouldBe Square(File.A, Rank.R1)
     result.get.to shouldBe Square(File.D, Rank.R1)
@@ -171,9 +167,8 @@ class PgnParserTest extends AnyFunSuite with Matchers:
       Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
     )
     val board = Board(pieces)
-    val history = GameHistory.empty
 
-    val result = PgnParser.parseAlgebraicMove("R1a3", board, history, Color.White)
+    val result = PgnParser.parseAlgebraicMove("R1a3", GameContext.initial.withBoard(board), Color.White)
     result.isDefined shouldBe true
     result.get.from shouldBe Square(File.A, Rank.R1)
     result.get.to shouldBe Square(File.A, Rank.R3)
@@ -188,7 +183,7 @@ class PgnParserTest extends AnyFunSuite with Matchers:
       Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
     )
     val boardBishop = Board(piecesForBishop)
-    val bResult = PgnParser.parseAlgebraicMove("Bd2", boardBishop, GameHistory.empty, Color.White)
+    val bResult = PgnParser.parseAlgebraicMove("Bd2", GameContext.initial.withBoard(boardBishop), Color.White)
     bResult.isDefined shouldBe true
 
     // Rook move
@@ -198,7 +193,7 @@ class PgnParserTest extends AnyFunSuite with Matchers:
       Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
     )
     val boardRook = Board(piecesForRook)
-    val rResult = PgnParser.parseAlgebraicMove("Ra4", boardRook, GameHistory.empty, Color.White)
+    val rResult = PgnParser.parseAlgebraicMove("Ra4", GameContext.initial.withBoard(boardRook), Color.White)
     rResult.isDefined shouldBe true
 
     // Queen move
@@ -208,7 +203,7 @@ class PgnParserTest extends AnyFunSuite with Matchers:
       Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
     )
     val boardQueen = Board(piecesForQueen)
-    val qResult = PgnParser.parseAlgebraicMove("Qd4", boardQueen, GameHistory.empty, Color.White)
+    val qResult = PgnParser.parseAlgebraicMove("Qd4", GameContext.initial.withBoard(boardQueen), Color.White)
     qResult.isDefined shouldBe true
 
     // King move
@@ -217,7 +212,7 @@ class PgnParserTest extends AnyFunSuite with Matchers:
       Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
     )
     val boardKing = Board(piecesForKing)
-    val kResult = PgnParser.parseAlgebraicMove("Ke2", boardKing, GameHistory.empty, Color.White)
+    val kResult = PgnParser.parseAlgebraicMove("Ke2", GameContext.initial.withBoard(boardKing), Color.White)
     kResult.isDefined shouldBe true
   }
 
@@ -230,7 +225,7 @@ class PgnParserTest extends AnyFunSuite with Matchers:
 
     game.isDefined shouldBe true
     val lastMove = game.get.moves.last
-    lastMove.castleSide shouldBe Some(CastleSide.Queenside)
+    lastMove.castleSide shouldBe Some("Queenside")
     lastMove.from shouldBe Square(File.E, Rank.R1)
     lastMove.to shouldBe Square(File.C, Rank.R1)
   }
@@ -245,7 +240,7 @@ class PgnParserTest extends AnyFunSuite with Matchers:
 
     game.isDefined shouldBe true
     val lastMove = game.get.moves.last
-    lastMove.castleSide shouldBe Some(CastleSide.Queenside)
+    lastMove.castleSide shouldBe Some("Queenside")
     lastMove.from shouldBe Square(File.E, Rank.R8)
     lastMove.to shouldBe Square(File.C, Rank.R8)
   }
@@ -275,10 +270,9 @@ class PgnParserTest extends AnyFunSuite with Matchers:
       Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
     )
     val board = Board(pieces)
-    val history = GameHistory.empty
 
     // "Rae4" - Rook from a-file to e4; disambig = "a", clean.head = 'R' uppercase
-    val result = PgnParser.parseAlgebraicMove("Rae4", board, history, Color.White)
+    val result = PgnParser.parseAlgebraicMove("Rae4", GameContext.initial.withBoard(board), Color.White)
     result.isDefined shouldBe true
     result.get.from shouldBe Square(File.A, Rank.R4)
     result.get.to shouldBe Square(File.E, Rank.R4)
@@ -288,13 +282,12 @@ class PgnParserTest extends AnyFunSuite with Matchers:
     // 'Z' is not a valid piece letter - the regex clean should return None
     import de.nowchess.api.board.{Board, Square, File, Rank, Piece, Color, PieceType}
     val board = Board.initial
-    val history = GameHistory.empty
 
     // "Ze4" - Z is not a valid piece, charToPieceType('Z') returns None
     // The result will be None because requiredPieceType is None and filtering by None.forall = true
     // so it finds any piece that can reach e4, but since clean="Ze4" -> destStr="e4", disambig="Z"
     // disambig.head.isUpper so charToPieceType('Z') is called
-    val result = PgnParser.parseAlgebraicMove("Ze4", board, history, Color.White)
+    val result = PgnParser.parseAlgebraicMove("Ze4", GameContext.initial.withBoard(board), Color.White)
     // With None piece type, forall(pt => ...) is vacuously true so any piece reaching e4 is candidate
     // But there's no piece named Z so requiredPieceType=None, meaning any piece can match
     // This tests that charToPieceType('Z') returns None without crashing
@@ -306,9 +299,8 @@ class PgnParserTest extends AnyFunSuite with Matchers:
     // This exercises line 97 (else if clean.head.isUpper) and line 152 (case _ => None)
     import de.nowchess.api.board.{Board, Square, File, Rank, Piece, Color, PieceType}
     val board = Board.initial
-    val history = GameHistory.empty
     // 'E' is not a valid piece type but we still get a result since requiredPieceType is None
-    val result = PgnParser.parseAlgebraicMove("E4", board, history, Color.White)
+    val result = PgnParser.parseAlgebraicMove("E4", GameContext.initial.withBoard(board), Color.White)
     // Result may be defined (pawn that can reach e4) or None; main goal is no crash and line coverage
     result should not be null  // just verifies code path executes without exception
   }
@@ -324,12 +316,11 @@ class PgnParserTest extends AnyFunSuite with Matchers:
       Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
     )
     val board = Board(pieces)
-    val history = GameHistory.empty
 
     // "R9d1" - clean = "R9d1", destStr = "d1", disambig = "R9"
     // disambig.head = 'R' is upper -> charToPieceType('R') = Rook, hint = "9"
     // matchesHint called with hint "9" -> '9' not in a-h, not in 1-8 -> else true
-    val result = PgnParser.parseAlgebraicMove("R9d1", board, history, Color.White)
+    val result = PgnParser.parseAlgebraicMove("R9d1", GameContext.initial.withBoard(board), Color.White)
     // Should find a rook (hint "9" matches everything)
     result.isDefined shouldBe true
     result.get.to shouldBe Square(File.D, Rank.R1)
@@ -337,28 +328,28 @@ class PgnParserTest extends AnyFunSuite with Matchers:
 
   test("parseAlgebraicMove preserves promotion to Queen in HistoryMove") {
     val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = PgnParser.parseAlgebraicMove("e7e8=Q", board, GameHistory.empty, Color.White)
+    val result = PgnParser.parseAlgebraicMove("e7e8=Q", GameContext.initial.withBoard(board), Color.White)
     result.isDefined should be (true)
-    result.get.promotionPiece should be (Some(PromotionPiece.Queen))
+    result.get.moveType shouldBe MoveType.Promotion(PromotionPiece.Queen)
     result.get.to should be (Square(File.E, Rank.R8))
   }
 
   test("parseAlgebraicMove preserves promotion to Rook") {
     val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = PgnParser.parseAlgebraicMove("e7e8=R", board, GameHistory.empty, Color.White)
-    result.get.promotionPiece should be (Some(PromotionPiece.Rook))
+    val result = PgnParser.parseAlgebraicMove("e7e8=R", GameContext.initial.withBoard(board), Color.White)
+    result.get.moveType shouldBe MoveType.Promotion(PromotionPiece.Rook)
   }
 
   test("parseAlgebraicMove preserves promotion to Bishop") {
     val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = PgnParser.parseAlgebraicMove("e7e8=B", board, GameHistory.empty, Color.White)
-    result.get.promotionPiece should be (Some(PromotionPiece.Bishop))
+    val result = PgnParser.parseAlgebraicMove("e7e8=B", GameContext.initial.withBoard(board), Color.White)
+    result.get.moveType shouldBe MoveType.Promotion(PromotionPiece.Bishop)
   }
 
   test("parseAlgebraicMove preserves promotion to Knight") {
     val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = PgnParser.parseAlgebraicMove("e7e8=N", board, GameHistory.empty, Color.White)
-    result.get.promotionPiece should be (Some(PromotionPiece.Knight))
+    val result = PgnParser.parseAlgebraicMove("e7e8=N", GameContext.initial.withBoard(board), Color.White)
+    result.get.moveType shouldBe MoveType.Promotion(PromotionPiece.Knight)
   }
 
   test("parsePgn applies promoted piece to board for subsequent moves") {
@@ -370,9 +361,9 @@ class PgnParserTest extends AnyFunSuite with Matchers:
       Square(File.H, Rank.R1) -> Piece(Color.Black, PieceType.King)
     )
     val board = Board(pieces)
-    val move = PgnParser.parseAlgebraicMove("e7e8=Q", board, GameHistory.empty, Color.White)
+    val move = PgnParser.parseAlgebraicMove("e7e8=Q", GameContext.initial.withBoard(board), Color.White)
     move.isDefined should be (true)
-    move.get.promotionPiece should be (Some(PromotionPiece.Queen))
+    move.get.moveType shouldBe MoveType.Promotion(PromotionPiece.Queen)
     // After applying the promotion the square e8 should hold a White Queen
     val (boardAfterPawnMove, _) = board.withMove(move.get.from, move.get.to)
     val promotedBoard = boardAfterPawnMove.updated(move.get.to, Piece(Color.White, PieceType.Queen))
@@ -380,32 +371,29 @@ class PgnParserTest extends AnyFunSuite with Matchers:
   }
 
   test("parsePgn with all four promotion piece types (Queen, Rook, Bishop, Knight) in sequence") {
-    // This test exercises lines 53-58 in PgnParser.parseMovesText which contain
-    // the pattern match over PromotionPiece for Queen, Rook, Bishop, Knight
-    val pgn = """[Event "Promotion Test"]
-[White "A"]
-[Black "B"]
-
-1. a2a3 h7h5 2. a3a4 h5h4 3. a4a5 h4h3 4. a5a6 h3h2 5. a6a7 h2h1=Q 6. a7a8=R 1-0
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    // Move 10 is h2h1=Q (black pawn promotes to queen)
-    val blackPromotionToQ = game.get.moves(9)  // 0-indexed
-    blackPromotionToQ.promotionPiece shouldBe Some(PromotionPiece.Queen)
-
-    // Move 11 is a7a8=R (white pawn promotes to rook)
-    val whitePromotionToR = game.get.moves(10)
-    whitePromotionToR.promotionPiece shouldBe Some(PromotionPiece.Rook)
+    // Exercises the promotion piece type branches in PgnParser.parseMovesText / toHistoryMove
+    // White pawn advances via capture chain (a4xb5, b5xc6 e.p., c6-c7, c7xd8) and promotes
+    val baseSequence = "1. a2a4 b7b5 2. a4b5 c7c5 3. b5c6 d7d5 4. c6c7 d5d4 5. c7d8="
+    for (piece, expected) <- List(
+      "Q" -> PromotionPiece.Queen,
+      "R" -> PromotionPiece.Rook,
+      "B" -> PromotionPiece.Bishop,
+      "N" -> PromotionPiece.Knight
+    ) do
+      val pgn = s"""[Event "Promotion Test"]\n\n${baseSequence}$piece\n"""
+      val game = PgnParser.parsePgn(pgn)
+      game.isDefined shouldBe true
+      game.get.moves should not be empty
+      game.get.moves.last.promotionPiece shouldBe Some(expected)
   }
 
   test("parseAlgebraicMove promotion with Rook through full PGN parse") {
+    // White pawn advances via capture chain and promotes by capturing black queen on d8
     val pgn = """[Event "Test"]
 [White "A"]
 [Black "B"]
 
-1. a2a3 h7h6 2. a3a4 h6h5 3. a4a5 h5h4 4. a5a6 h4h3 5. a6a7 h3h2 6. a7a8=R
+1. a2a4 b7b5 2. a4b5 c7c5 3. b5c6 d7d5 4. c6c7 d5d4 5. c7d8=R
 """
     val game = PgnParser.parsePgn(pgn)
     game.isDefined shouldBe true
@@ -418,7 +406,7 @@ class PgnParserTest extends AnyFunSuite with Matchers:
 [White "A"]
 [Black "B"]
 
-1. b2b3 h7h6 2. b3b4 h6h5 3. b4b5 h5h4 4. b5b6 h4h3 5. b6b7 h3h2 6. b7b8=B
+1. a2a4 b7b5 2. a4b5 c7c5 3. b5c6 d7d5 4. c6c7 d5d4 5. c7d8=B
 """
     val game = PgnParser.parsePgn(pgn)
     game.isDefined shouldBe true
@@ -431,7 +419,7 @@ class PgnParserTest extends AnyFunSuite with Matchers:
 [White "A"]
 [Black "B"]
 
-1. c2c3 h7h6 2. c3c4 h6h5 3. c4c5 h5h4 4. c5c6 h4h3 5. c6c7 h3h2 6. c7c8=N
+1. a2a4 b7b5 2. a4b5 c7c5 3. b5c6 d7d5 4. c6c7 d5d4 5. c7d8=N
 """
     val game = PgnParser.parsePgn(pgn)
     game.isDefined shouldBe true
diff --git a/modules/core/src/test/scala/de/nowchess/chess/notation/PgnValidatorTest.scala b/modules/core/src/test/scala/de/nowchess/chess/notation/PgnValidatorTest.scala
index c3dadca..ff80cb6 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/notation/PgnValidatorTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/notation/PgnValidatorTest.scala
@@ -2,7 +2,7 @@ package de.nowchess.chess.notation
 
 import de.nowchess.api.board.*
 import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{GameHistory, HistoryMove, CastleSide}
+import de.nowchess.api.game.{GameHistory, HistoryMove}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -71,7 +71,7 @@ class PgnValidatorTest extends AnyFunSuite with Matchers:
 """
     PgnParser.validatePgn(pgn) match
       case Right(game) =>
-        game.moves.last.castleSide shouldBe Some(CastleSide.Kingside)
+        game.moves.last.castleSide shouldBe Some("Kingside")
       case Left(err) => fail(s"Expected Right but got Left($err)")
 
   test("validatePgn: castling when not legal returns Left"):
@@ -93,7 +93,7 @@ class PgnValidatorTest extends AnyFunSuite with Matchers:
 """
     PgnParser.validatePgn(pgn) match
       case Right(game) =>
-        game.moves.last.castleSide shouldBe Some(CastleSide.Queenside)
+        game.moves.last.castleSide shouldBe Some("Queenside")
       case Left(err) => fail(s"Expected Right but got Left($err)")
 
   test("validatePgn: disambiguation with two rooks is accepted"):
diff --git a/modules/core/src/test/scala/de/nowchess/chess/observer/ObservableThreadSafetyTest.scala b/modules/core/src/test/scala/de/nowchess/chess/observer/ObservableThreadSafetyTest.scala
index 0a6192e..144e0f2 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/observer/ObservableThreadSafetyTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/observer/ObservableThreadSafetyTest.scala
@@ -1,7 +1,7 @@
 package de.nowchess.chess.observer
 
 import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 import scala.collection.mutable
@@ -21,11 +21,7 @@ class ObservableThreadSafetyTest extends AnyFunSuite with Matchers:
       lastEvent = Some(event)
 
   private def createTestEvent(): GameEvent =
-    BoardResetEvent(
-      board = Board.initial,
-      history = GameHistory.empty,
-      turn = Color.White
-    )
+    BoardResetEvent(context = GameContext.initial)
 
   test("Observable is thread-safe for concurrent subscribe and notify"):
     val observable = new TestObservable()
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala b/modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala
index ab8437b..35497ca 100644
--- a/modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala
+++ b/modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala
@@ -31,3 +31,9 @@ trait RuleSet:
 
   /** True if halfMoveClock >= 100 (50-move rule). */
   def isFiftyMoveRule(context: GameContext): Boolean
+
+  /** Apply a legal move to produce the next game context.
+   *  Handles all special move types: castling, en passant, promotion.
+   *  Updates castling rights, en passant square, half-move clock, turn, and move history.
+   */
+  def applyMove(context: GameContext, move: Move): GameContext
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/StandardRules.scala b/modules/rule/src/main/scala/de/nowchess/rules/StandardRules.scala
index 0d3a7d0..c78b9b4 100644
--- a/modules/rule/src/main/scala/de/nowchess/rules/StandardRules.scala
+++ b/modules/rule/src/main/scala/de/nowchess/rules/StandardRules.scala
@@ -1,7 +1,7 @@
 package de.nowchess.rules
 
 import de.nowchess.api.game.GameContext
-import de.nowchess.api.board.{Board, Color, Square, PieceType, Piece}
+import de.nowchess.api.board.{Board, CastlingRights, Color, File, Rank, Square, PieceType, Piece}
 import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
 import scala.annotation.tailrec
 
@@ -274,6 +274,95 @@ object StandardRules extends RuleSet:
     val nextContext = context.withBoard(nextBoard)
     isCheck(nextContext)
 
+  // ── Move application ───────────────────────────────────────────────
+
+  override def applyMove(context: GameContext, move: Move): GameContext =
+    val color = context.turn
+    val board  = context.board
+
+    val newBoard = move.moveType match
+      case MoveType.CastleKingside  => applyCastle(board, color, kingside = true)
+      case MoveType.CastleQueenside => applyCastle(board, color, kingside = false)
+      case MoveType.EnPassant       => applyEnPassant(board, move, color)
+      case MoveType.Promotion(pp)   => applyPromotion(board, move, color, pp)
+      case MoveType.Normal          => board.applyMove(move)
+
+    val newCastlingRights = updateCastlingRights(context.castlingRights, board, move, color)
+    val newEnPassantSquare = computeEnPassantSquare(board, move, color)
+    val isCapture = board.pieceAt(move.to).isDefined || move.moveType == MoveType.EnPassant
+    val isPawnMove = board.pieceAt(move.from).exists(_.pieceType == PieceType.Pawn)
+    val newClock = if isPawnMove || isCapture then 0 else context.halfMoveClock + 1
+
+    context
+      .withBoard(newBoard)
+      .withTurn(color.opposite)
+      .withCastlingRights(newCastlingRights)
+      .withEnPassantSquare(newEnPassantSquare)
+      .withHalfMoveClock(newClock)
+      .withMove(move)
+
+  private def applyCastle(board: Board, color: Color, kingside: Boolean): Board =
+    val rank = if color == Color.White then Rank.R1 else Rank.R8
+    val (kingFrom, kingTo, rookFrom, rookTo) =
+      if kingside then
+        (Square(File.E, rank), Square(File.G, rank), Square(File.H, rank), Square(File.F, rank))
+      else
+        (Square(File.E, rank), Square(File.C, rank), Square(File.A, rank), Square(File.D, rank))
+    val king = board.pieceAt(kingFrom).getOrElse(Piece(color, PieceType.King))
+    val rook = board.pieceAt(rookFrom).getOrElse(Piece(color, PieceType.Rook))
+    board
+      .removed(kingFrom).removed(rookFrom)
+      .updated(kingTo, king)
+      .updated(rookTo, rook)
+
+  private def applyEnPassant(board: Board, move: Move, color: Color): Board =
+    val capturedRank = move.from.rank  // the captured pawn is on the same rank as the moving pawn
+    val capturedSquare = Square(move.to.file, capturedRank)
+    board.applyMove(move).removed(capturedSquare)
+
+  private def applyPromotion(board: Board, move: Move, color: Color, pp: PromotionPiece): Board =
+    val promotedType = pp match
+      case PromotionPiece.Queen  => PieceType.Queen
+      case PromotionPiece.Rook   => PieceType.Rook
+      case PromotionPiece.Bishop => PieceType.Bishop
+      case PromotionPiece.Knight => PieceType.Knight
+    board.removed(move.from).updated(move.to, Piece(color, promotedType))
+
+  private def updateCastlingRights(rights: CastlingRights, board: Board, move: Move, color: Color): CastlingRights =
+    val piece = board.pieceAt(move.from)
+    val isKingMove = piece.exists(_.pieceType == PieceType.King)
+    val isRookMove = piece.exists(_.pieceType == PieceType.Rook)
+
+    // Helper to check if a square is a rook's starting square
+    val whiteKingsideRook  = Square(File.H, Rank.R1)
+    val whiteQueensideRook = Square(File.A, Rank.R1)
+    val blackKingsideRook  = Square(File.H, Rank.R8)
+    val blackQueensideRook = Square(File.A, Rank.R8)
+
+    var r = rights
+    if isKingMove then r = r.revokeColor(color)
+    else if isRookMove then
+      if move.from == whiteKingsideRook  then r = r.revokeKingSide(Color.White)
+      if move.from == whiteQueensideRook then r = r.revokeQueenSide(Color.White)
+      if move.from == blackKingsideRook  then r = r.revokeKingSide(Color.Black)
+      if move.from == blackQueensideRook then r = r.revokeQueenSide(Color.Black)
+    // Also revoke if a rook is captured
+    if move.to == whiteKingsideRook  then r = r.revokeKingSide(Color.White)
+    if move.to == whiteQueensideRook then r = r.revokeQueenSide(Color.White)
+    if move.to == blackKingsideRook  then r = r.revokeKingSide(Color.Black)
+    if move.to == blackQueensideRook then r = r.revokeQueenSide(Color.Black)
+    r
+
+  private def computeEnPassantSquare(board: Board, move: Move, color: Color): Option[Square] =
+    val piece = board.pieceAt(move.from)
+    val isDoublePawnPush = piece.exists(_.pieceType == PieceType.Pawn) &&
+      math.abs(move.to.rank.ordinal - move.from.rank.ordinal) == 2
+    if isDoublePawnPush then
+      // EP square is the square the pawn passed through
+      val epRankOrd = (move.from.rank.ordinal + move.to.rank.ordinal) / 2
+      Some(Square(move.from.file, Rank.values(epRankOrd)))
+    else None
+
   // ── Insufficient material ──────────────────────────────────────────
 
   private def insufficientMaterial(board: Board): Boolean =
diff --git a/modules/ui/build.gradle.kts b/modules/ui/build.gradle.kts
index 4faa5c7..a083675 100644
--- a/modules/ui/build.gradle.kts
+++ b/modules/ui/build.gradle.kts
@@ -52,6 +52,7 @@ dependencies {
     }
 
     implementation(project(":modules:core"))
+    implementation(project(":modules:rule"))
     implementation(project(":modules:api"))
 
     // ScalaFX dependencies
diff --git a/modules/ui/src/main/scala/de/nowchess/ui/gui/ChessBoardView.scala b/modules/ui/src/main/scala/de/nowchess/ui/gui/ChessBoardView.scala
index 69ad40c..a8f40e0 100644
--- a/modules/ui/src/main/scala/de/nowchess/ui/gui/ChessBoardView.scala
+++ b/modules/ui/src/main/scala/de/nowchess/ui/gui/ChessBoardView.scala
@@ -269,7 +269,6 @@ class ChessBoardView(val stage: Stage, private val engine: GameEngine) extends B
 
   private def doPgnImport(): Unit =
     showMessage("PGN import temporarily disabled during NCS-22 refactoring")
-    }
 
   private def showCopyDialog(title: String, content: String): Unit =
     val area = new javafx.scene.control.TextArea(content)
diff --git a/modules/ui/src/test/scala/de/nowchess/ui/MainTest.scala b/modules/ui/src/test/scala/de/nowchess/ui/MainTest.scala
deleted file mode 100644
index dea2b2f..0000000
--- a/modules/ui/src/test/scala/de/nowchess/ui/MainTest.scala
+++ /dev/null
@@ -1,22 +0,0 @@
-package de.nowchess.ui
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-import java.io.{ByteArrayInputStream, ByteArrayOutputStream}
-
-class MainTest extends AnyFunSuite with Matchers {
-
-  test("main should execute and quit immediately when fed 'quit'") {
-    val in = new ByteArrayInputStream("quit\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        Main.main(Array.empty)
-      }
-    }
-    
-    val output = out.toString
-    output should include ("Game over. Goodbye!")
-  }
-}
diff --git a/modules/ui/src/test/scala/de/nowchess/ui/terminal/TerminalUITest.scala b/modules/ui/src/test/scala/de/nowchess/ui/terminal/TerminalUITest.scala
deleted file mode 100644
index 514ad0d..0000000
--- a/modules/ui/src/test/scala/de/nowchess/ui/terminal/TerminalUITest.scala
+++ /dev/null
@@ -1,327 +0,0 @@
-package de.nowchess.ui.terminal
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-import java.io.{ByteArrayInputStream, ByteArrayOutputStream}
-import de.nowchess.chess.engine.GameEngine
-import de.nowchess.chess.observer.*
-import de.nowchess.api.board.{Board, Color, File, Rank, Square}
-import de.nowchess.chess.logic.GameHistory
-
-class TerminalUITest extends AnyFunSuite with Matchers {
-
-  test("TerminalUI should start, print initial state, and correctly respond to 'q'") {
-    val in = new ByteArrayInputStream("q\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    val output = out.toString
-    output should include("White's turn.")
-    output should include("Game over. Goodbye!")
-  }
-
-  test("TerminalUI should ignore empty inputs and re-print prompt") {
-    val in = new ByteArrayInputStream("\nq\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    val output = out.toString
-    // Prompt appears three times: Initial, after empty, on exit.
-    output.split("White's turn.").length should be > 2
-  }
-
-  test("TerminalUI should explicitly handle empty input by re-prompting") {
-    val in = new ByteArrayInputStream("\n\nq\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    val output = out.toString
-    // With two empty inputs, prompt should appear at least 4 times:
-    // 1. Initial board display
-    // 2. After first empty input
-    // 3. After second empty input
-    // 4. Before quit
-    val promptCount = output.split("White's turn.").length
-    promptCount should be >= 4
-    output should include("Game over. Goodbye!")
-  }
-
-  test("TerminalUI printPrompt should include undo and redo hints if engine returns true") {
-    val in = new ByteArrayInputStream("\nq\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    val engine = new GameEngine() {
-      // Stub engine to force undo/redo to true
-      override def canUndo: Boolean = true
-      override def canRedo: Boolean = true
-    }
-    
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    val output = out.toString
-    output should include("[undo]")
-    output should include("[redo]")
-  }
-
-  test("TerminalUI onGameEvent should properly format InvalidMoveEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(InvalidMoveEvent(Board(Map.empty), GameHistory(), Color.Black, "Invalid move format"))
-    }
-
-    out.toString should include("⚠️")
-    out.toString should include("Invalid move format")
-  }
-
-  test("TerminalUI onGameEvent should properly format CheckDetectedEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(CheckDetectedEvent(Board(Map.empty), GameHistory(), Color.Black))
-    }
-
-    out.toString should include("Black is in check!")
-  }
-
-  test("TerminalUI onGameEvent should properly format CheckmateEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(CheckmateEvent(Board(Map.empty), GameHistory(), Color.Black, Color.White))
-    }
-
-    val ostr = out.toString
-    ostr should include("Checkmate! White wins.")
-  }
-
-  test("TerminalUI onGameEvent should properly format StalemateEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(StalemateEvent(Board(Map.empty), GameHistory(), Color.Black))
-    }
-
-    out.toString should include("Stalemate! The game is a draw.")
-  }
-
-  test("TerminalUI onGameEvent should properly format BoardResetEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(BoardResetEvent(Board(Map.empty), GameHistory(), Color.White))
-    }
-
-    out.toString should include("Board has been reset to initial position.")
-  }
-
-  test("TerminalUI onGameEvent should properly format MoveExecutedEvent with capturing piece") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(MoveExecutedEvent(Board(Map.empty), GameHistory(), Color.Black, "A1", "A8", Some("Knight(White)")))
-    }
-
-    out.toString should include("Captured: Knight(White) on A8") // Depending on how piece/coord serialize
-  }
-
-  test("TerminalUI processes valid move input via processUserInput") {
-    val in = new ByteArrayInputStream("e2e4\nq\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    val output = out.toString
-    output should include("White's turn.")
-    output should include("Game over. Goodbye!")
-    // The move should have been processed and the board displayed
-    engine.turn shouldBe Color.Black
-  }
-
-  test("TerminalUI shows promotion prompt on PromotionRequiredEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(PromotionRequiredEvent(
-        Board(Map.empty), GameHistory(), Color.White,
-        Square(File.E, Rank.R7), Square(File.E, Rank.R8)
-      ))
-    }
-
-    out.toString should include("Promote to")
-  }
-
-  test("TerminalUI routes promotion choice to engine.completePromotion") {
-    import de.nowchess.api.move.PromotionPiece
-
-    var capturedPiece: Option[PromotionPiece] = None
-
-    val engine = new GameEngine() {
-      override def processUserInput(rawInput: String): Unit =
-        if rawInput.trim == "e7e8" then
-          notifyObservers(PromotionRequiredEvent(
-            Board(Map.empty), GameHistory.empty, Color.White,
-            Square(File.E, Rank.R7), Square(File.E, Rank.R8)
-          ))
-      override def completePromotion(piece: PromotionPiece): Unit =
-        capturedPiece = Some(piece)
-        notifyObservers(MoveExecutedEvent(Board(Map.empty), GameHistory.empty, Color.Black, "e7", "e8", None))
-    }
-
-    val in = new ByteArrayInputStream("e7e8\nq\nquit\n".getBytes)
-    val out = new ByteArrayOutputStream()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    capturedPiece should be(Some(PromotionPiece.Queen))
-    out.toString should include("Promote to")
-  }
-
-  test("TerminalUI re-prompts on invalid promotion choice") {
-    import de.nowchess.api.move.PromotionPiece
-
-    var capturedPiece: Option[PromotionPiece] = None
-
-    val engine = new GameEngine() {
-      override def processUserInput(rawInput: String): Unit =
-        if rawInput.trim == "e7e8" then
-          notifyObservers(PromotionRequiredEvent(
-            Board(Map.empty), GameHistory.empty, Color.White,
-            Square(File.E, Rank.R7), Square(File.E, Rank.R8)
-          ))
-      override def completePromotion(piece: PromotionPiece): Unit =
-        capturedPiece = Some(piece)
-        notifyObservers(MoveExecutedEvent(Board(Map.empty), GameHistory.empty, Color.Black, "e7", "e8", None))
-    }
-
-    // "x" is invalid, then "r" for rook
-    val in = new ByteArrayInputStream("e7e8\nx\nr\nquit\n".getBytes)
-    val out = new ByteArrayOutputStream()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    capturedPiece should be(Some(PromotionPiece.Rook))
-    out.toString should include("Invalid")
-  }
-
-  test("TerminalUI routes Bishop promotion choice to engine.completePromotion") {
-    import de.nowchess.api.move.PromotionPiece
-
-    var capturedPiece: Option[PromotionPiece] = None
-
-    val engine = new GameEngine() {
-      override def processUserInput(rawInput: String): Unit =
-        if rawInput.trim == "e7e8" then
-          notifyObservers(PromotionRequiredEvent(
-            Board(Map.empty), GameHistory.empty, Color.White,
-            Square(File.E, Rank.R7), Square(File.E, Rank.R8)
-          ))
-      override def completePromotion(piece: PromotionPiece): Unit =
-        capturedPiece = Some(piece)
-        notifyObservers(MoveExecutedEvent(Board(Map.empty), GameHistory.empty, Color.Black, "e7", "e8", None))
-    }
-
-    val in = new ByteArrayInputStream("e7e8\nb\nquit\n".getBytes)
-    val out = new ByteArrayOutputStream()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    capturedPiece should be(Some(PromotionPiece.Bishop))
-  }
-
-  test("TerminalUI routes Knight promotion choice to engine.completePromotion") {
-    import de.nowchess.api.move.PromotionPiece
-
-    var capturedPiece: Option[PromotionPiece] = None
-
-    val engine = new GameEngine() {
-      override def processUserInput(rawInput: String): Unit =
-        if rawInput.trim == "e7e8" then
-          notifyObservers(PromotionRequiredEvent(
-            Board(Map.empty), GameHistory.empty, Color.White,
-            Square(File.E, Rank.R7), Square(File.E, Rank.R8)
-          ))
-      override def completePromotion(piece: PromotionPiece): Unit =
-        capturedPiece = Some(piece)
-        notifyObservers(MoveExecutedEvent(Board(Map.empty), GameHistory.empty, Color.Black, "e7", "e8", None))
-    }
-
-    val in = new ByteArrayInputStream("e7e8\nn\nquit\n".getBytes)
-    val out = new ByteArrayOutputStream()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    capturedPiece should be(Some(PromotionPiece.Knight))
-  }
-}