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 906987e..ab8437b 100644
--- a/modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala
+++ b/modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala
@@ -1,29 +1,33 @@
 package de.nowchess.rules
 
-import de.nowchess.chess.{Move, Situation, Square}
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.board.Square
+import de.nowchess.api.move.Move
 
-/** Extension point for chess rule variants. Implement to support Chess960, etc. */
+/** Extension point for chess rule variants (standard, Chess960, etc.).
+ *  All rule queries are stateless: given a GameContext, return the answer.
+ */
 trait RuleSet:
   /** All pseudo-legal moves for the piece on `square` (ignores check). */
-  def candidateMoves(situation: Situation, square: Square): List[Move]
+  def candidateMoves(context: GameContext, square: Square): List[Move]
 
   /** Legal moves for `square`: candidates that don't leave own king in check. */
-  def legalMoves(situation: Situation, square: Square): List[Move]
+  def legalMoves(context: GameContext, square: Square): List[Move]
 
   /** All legal moves for the side to move. */
-  def allLegalMoves(situation: Situation): List[Move]
+  def allLegalMoves(context: GameContext): List[Move]
 
   /** True if the side to move's king is in check. */
-  def isCheck(situation: Situation): Boolean
+  def isCheck(context: GameContext): Boolean
 
   /** True if the side to move is in check and has no legal moves. */
-  def isCheckmate(situation: Situation): Boolean
+  def isCheckmate(context: GameContext): Boolean
 
   /** True if the side to move is not in check and has no legal moves. */
-  def isStalemate(situation: Situation): Boolean
+  def isStalemate(context: GameContext): Boolean
 
   /** True if neither side has enough material to checkmate. */
-  def isInsufficientMaterial(situation: Situation): Boolean
+  def isInsufficientMaterial(context: GameContext): Boolean
 
   /** True if halfMoveClock >= 100 (50-move rule). */
-  def isFiftyMoveRule(situation: Situation): Boolean
+  def isFiftyMoveRule(context: GameContext): Boolean