diff --git a/modules/core/src/main/scala/de/nowchess/chess/view/Renderer.scala b/modules/core/src/main/scala/de/nowchess/chess/view/Renderer.scala
index 3a7fafa..b572860 100644
--- a/modules/core/src/main/scala/de/nowchess/chess/view/Renderer.scala
+++ b/modules/core/src/main/scala/de/nowchess/chess/view/Renderer.scala
@@ -11,21 +11,18 @@ object Renderer:
   private val AnsiBlackPiece  = "\u001b[30m"         // black text
 
   def render(board: Board): String =
-    val sb = new StringBuilder
-    sb.append("  a  b  c  d  e  f  g  h\n")
-    for rank <- (0 until 8).reverse do
-      sb.append(s"${rank + 1} ")
-      for file <- 0 until 8 do
-        val sq          = Square(File.values(file), Rank.values(rank))
-        val isLightSq   = (file + rank) % 2 != 0
-        val bgColor     = if isLightSq then AnsiLightSquare else AnsiDarkSquare
-        val cellContent = board.pieceAt(sq) match
+    val rows = (0 until 8).reverse.map { rank =>
+      val cells = (0 until 8).map { file =>
+        val sq        = Square(File.values(file), Rank.values(rank))
+        val isLightSq = (file + rank) % 2 != 0
+        val bgColor   = if isLightSq then AnsiLightSquare else AnsiDarkSquare
+        board.pieceAt(sq) match
           case Some(piece) =>
             val fgColor = if piece.color == Color.White then AnsiWhitePiece else AnsiBlackPiece
             s"$bgColor$fgColor ${piece.unicode} $AnsiReset"
           case None =>
             s"$bgColor   $AnsiReset"
-        sb.append(cellContent)
-      sb.append(s" ${rank + 1}\n")
-    sb.append("  a  b  c  d  e  f  g  h\n")
-    sb.toString
+      }.mkString
+      s"${rank + 1} $cells ${rank + 1}"
+    }.mkString("\n")
+    s"  a  b  c  d  e  f  g  h\n$rows\n  a  b  c  d  e  f  g  h\n"