Fixed input listening bug in NaturalPlayer

+ disconnect methods in Game and Player
+ NaturalPlayer removes its MouseListener from OverlayComponent after
the disconnect method is called

.classpath

@@ -1,12 +1,17 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <classpath>
 	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="src" path="res"/>
+	<classpathentry kind="src" output="bin_test" path="test">
+		<attributes>
+			<attribute name="test" value="true"/>
+		</attributes>
+	</classpathentry>
 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER">
 		<attributes>
 			<attribute name="module" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry kind="lib" path="res"/>
 	<classpathentry kind="con" path="org.eclipse.jdt.junit.JUNIT_CONTAINER/5"/>
 	<classpathentry kind="output" path="bin"/>
 </classpath>

.gitignore

@@ -1,5 +1,6 @@
 .metadata
 bin/
+/bin_test/
 tmp/
 *.tmp
 *.bak
@@ -20,4 +21,4 @@ local.properties
 .recommenders/
 
 # Annotation Processing
-.apt_generated/
+.apt_generated/

src/dev/kske/chess/board/Board.java

@@ -5,6 +5,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import dev.kske.chess.board.Log.LoggedMove;
 import dev.kske.chess.board.Piece.Color;
 import dev.kske.chess.board.Piece.Type;
 
@@ -18,10 +19,49 @@ public class Board implements Cloneable {
 
 	private Piece[][]				boardArr;
 	private Map<Color, Position>	kingPos;
+	private Log						log;
+
+	private static final Map<Type, int[][]> positionScores;
+
+	static {
+		positionScores = new HashMap<>();
+		positionScores.put(Type.KING,
+				new int[][] { new int[] { -3, -4, -4, -5, -5, -4, -4, -3 },
+						new int[] { -3, -4, -4, -5, -4, -4, -4, -3 }, new int[] { -3, -4, -4, -5, -4, -4, -4, -3 },
+						new int[] { -3, -4, -4, -5, -4, -4, -4, -3 }, new int[] { -2, -3, -3, -2, -2, -2, -2, -1 },
+						new int[] { -1, -2, -2, -2, -2, -2, -2, -1 }, new int[] { 2, 2, 0, 0, 0, 0, 2, 2 },
+						new int[] { 2, 3, 1, 0, 0, 1, 3, 2 } });
+		positionScores.put(Type.QUEEN,
+				new int[][] { new int[] { -2, -1, -1, -1, -1, -1, -1, -2 }, new int[] { -1, 0, 0, 0, 0, 0, 0, -1 },
+						new int[] { -1, 0, 1, 1, 1, 1, 0, -1 }, new int[] { -1, 0, 1, 1, 1, 1, 0, -1 },
+						new int[] { 0, 0, 1, 1, 1, 1, 0, -1 }, new int[] { -1, 1, 1, 1, 1, 1, 0, -1 },
+						new int[] { -1, 0, 1, 0, 0, 0, 0, -1 }, new int[] { -2, -1, -1, -1, -1, -1, -1, -2 } });
+		positionScores.put(Type.ROOK,
+				new int[][] { new int[] { 0, 0, 0, 0, 0, 0, 0, 0 }, new int[] { 1, 1, 1, 1, 1, 1, 1, 1 },
+						new int[] { -1, 0, 0, 0, 0, 0, 0, -1 }, new int[] { -1, 0, 0, 0, 0, 0, 0, -1 },
+						new int[] { -1, 0, 0, 0, 0, 0, 0, -1 }, new int[] { -1, 0, 0, 0, 0, 0, 0, -1 },
+						new int[] { -1, 0, 0, 0, 0, 0, 0, -1 }, new int[] { 0, 0, 0, 1, 1, 0, 0, 0 } });
+		positionScores.put(Type.KNIGHT,
+				new int[][] { new int[] { -5, -4, -3, -3, -3, -3, -4, -5 }, new int[] { -4, -2, 0, 0, 0, 0, -2, -4 },
+						new int[] { -3, 0, 1, 2, 2, 1, 0, -3 }, new int[] { -3, 1, 2, 2, 2, 2, 1, -3 },
+						new int[] { -3, 0, 2, 2, 2, 2, 0, -1 }, new int[] { -3, 1, 1, 2, 2, 1, 1, -3 },
+						new int[] { -4, -2, 0, 1, 1, 0, -2, -4 }, new int[] { -5, -4, -3, -3, -3, -3, -4, -5 } });
+		positionScores.put(Type.BISHOP,
+				new int[][] { new int[] { -2, -1, -1, -1, -1, -1, -1, 2 }, new int[] { -1, 0, 0, 0, 0, 0, 0, -1 },
+						new int[] { -1, 0, 1, 1, 1, 1, 0, -1 }, new int[] { -1, 1, 1, 1, 1, 1, 1, -1 },
+						new int[] { -1, 0, 1, 1, 1, 1, 0, -1 }, new int[] { -1, 1, 1, 1, 1, 1, 1, -1 },
+						new int[] { -1, 1, 0, 0, 0, 0, 1, -1 }, new int[] { -2, -1, -1, -1, -1, -1, -1, -2 } });
+		positionScores.put(Type.PAWN,
+				new int[][] { new int[] { 0, 0, 0, 0, 0, 0, 0, 0 }, new int[] { 5, 5, 5, 5, 5, 5, 5, 5 },
+						new int[] { 1, 1, 2, 3, 3, 2, 1, 1 }, new int[] { 0, 0, 1, 3, 3, 1, 0, 0 },
+						new int[] { 0, 0, 0, 2, 2, 0, 0, 0 }, new int[] { 0, 0, -1, 0, 0, -1, 0, 0 },
+						new int[] { 0, 1, 1, -2, -2, 1, 1, 0 }, new int[] { 0, 0, 0, 0, 0, 0, 0, 0 } });
+	}
 
 	public Board() {
-		boardArr			= new Piece[8][8];
-		kingPos				= new HashMap<>();
+		boardArr	= new Piece[8][8];
+		kingPos		= new HashMap<>();
+		log			= new Log();
 		initializeDefaultPositions();
 	}
 
@@ -35,12 +75,15 @@ public class Board implements Cloneable {
 		Piece piece = getPos(move);
 		if (piece == null || !piece.isValidMove(move)) return false;
 		else {
+			// Set type after validation
+			if (move.type == Move.Type.UNKNOWN) move.type = Move.Type.NORMAL;
+
 			// Move piece
-			Piece capturePiece = move(move);
+			move(move);
 
 			// Revert move if it caused a check for its team
 			if (checkCheck(piece.getColor())) {
-				revert(move, capturePiece);
+				revert();
 				return false;
 			}
 
@@ -54,31 +97,97 @@ public class Board implements Cloneable {
 	 * @param move The move to execute
 	 * @return The captures piece, or null if the move's destination was empty
 	 */
-	public Piece move(Move move) {
+	public void move(Move move) {
 		Piece	piece			= getPos(move);
 		Piece	capturePiece	= getDest(move);
-		setDest(move, piece);
-		setPos(move, null);
+
+		switch (move.type) {
+			case PAWN_PROMOTION:
+				setPos(move, null);
+				// TODO: Select promotion
+				setDest(move, new Queen(piece.getColor(), this));
+				break;
+			case CASTLING:
+				// Move the king
+				setDest(move, piece);
+				setPos(move, null);
+
+				// Move the rook
+				Move rookMove = move.dest.x == 6 ? new Move(7, move.pos.y, 5, move.pos.y) // Kingside
+						: new Move(0, move.pos.y, 3, move.pos.y); // Queenside
+
+				// Move the rook
+				setDest(rookMove, getPos(rookMove));
+				setPos(rookMove, null);
+
+				getDest(rookMove).incMoveCounter();
+				break;
+			case UNKNOWN:
+				System.err.printf("Move of unknown type %s found!%n", move);
+			case NORMAL:
+				setDest(move, piece);
+				setPos(move, null);
+				break;
+			default:
+				System.err.printf("Move %s of unimplemented type found!%n", move);
+		}
+
+		// Increment move counter
+		getDest(move).incMoveCounter();
 
 		// Update the king's position if the moved piece is the king
 		if (piece.getType() == Type.KING) kingPos.put(piece.getColor(), move.dest);
 
-		return capturePiece;
+		// Update log
+		log.add(move, capturePiece);
 	}
 
 	/**
-	 * Reverts a move.
-	 * 
-	 * @param move          The move to revert
-	 * @param capturedPiece The piece that has been captured when the move has been
-	 *                      applied
+	 * Reverts the last move.
 	 */
-	public void revert(Move move, Piece capturedPiece) {
-		setPos(move, getDest(move));
-		setDest(move, capturedPiece);
+	public void revert() {
+		LoggedMove	loggedMove		= log.getLast();
+		Move		move			= loggedMove.move;
+		Piece		capturedPiece	= loggedMove.capturedPiece;
+
+		switch (move.type) {
+			case PAWN_PROMOTION:
+				setPos(move, new Pawn(getDest(move).getColor(), this));
+				setDest(move, capturedPiece);
+				break;
+			case CASTLING:
+				// Move the king
+				setPos(move, getDest(move));
+				setDest(move, null);
+
+				// Move the rook
+				Move rookMove = move.dest.x == 6 ? new Move(5, move.pos.y, 7, move.pos.y) // Kingside
+						: new Move(3, move.pos.y, 0, move.pos.y); // Queenside
+
+				// Move the rook
+				setDest(rookMove, getPos(rookMove));
+				setPos(rookMove, null);
+
+				getDest(rookMove).decMoveCounter();
+				break;
+			case UNKNOWN:
+				System.err.printf("Move of unknown type %s found!%n", move);
+			case NORMAL:
+				setPos(move, getDest(move));
+				setDest(move, capturedPiece);
+				break;
+			default:
+				System.err.printf("Move %s of unimplemented type found!%n", move);
+		}
+
+		// Decrement move counter
+		getPos(move).decMoveCounter();
 
 		// Update the king's position if the moved piece is the king
 		if (getPos(move).getType() == Type.KING) kingPos.put(getPos(move).getColor(), move.pos);
+
+		// Update log
+		log.removeLast();
 	}
 
 	/**
@@ -129,9 +238,9 @@ public class Board implements Cloneable {
 		if (!getMoves(kingPos.get(color)).isEmpty()) return false;
 		else {
 			for (Move move : getMoves(color)) {
-				Piece	capturePiece	= move(move);
-				boolean	check			= checkCheck(color);
-				revert(move, capturePiece);
+				move(move);
+				boolean check = checkCheck(color);
+				revert();
 				if (!check) return false;
 			}
 			return true;
@@ -139,8 +248,7 @@ public class Board implements Cloneable {
 	}
 
 	public GameState getGameEventType(Color color) {
-		return checkCheck(color)
-				? checkCheckmate(color) ? GameState.CHECKMATE : GameState.CHECK
+		return checkCheck(color) ? checkCheckmate(color) ? GameState.CHECKMATE : GameState.CHECK
 				: getMoves(color).isEmpty() ? GameState.STALEMATE : GameState.NORMAL;
 	}
 
@@ -154,22 +262,26 @@ public class Board implements Cloneable {
 		int score = 0;
 		for (int i = 0; i < 8; i++)
 			for (int j = 0; j < 8; j++)
-				if (boardArr[i][j] != null && boardArr[i][j].getColor() == color) switch (boardArr[i][j].getType()) {
-					case QUEEN:
-						score += 8;
-						break;
-					case ROOK:
-						score += 5;
-						break;
-					case KNIGHT:
-						score += 3;
-						break;
-					case BISHOP:
-						score += 3;
-						break;
-					case PAWN:
-						score += 1;
-						break;
+				if (boardArr[i][j] != null && boardArr[i][j].getColor() == color) {
+					switch (boardArr[i][j].getType()) {
+						case QUEEN:
+							score += 90;
+							break;
+						case ROOK:
+							score += 50;
+							break;
+						case KNIGHT:
+							score += 30;
+							break;
+						case BISHOP:
+							score += 30;
+							break;
+						case PAWN:
+							score += 10;
+							break;
+					}
+					if (positionScores.containsKey(boardArr[i][j].getType()))
+						score += positionScores.get(boardArr[i][j].getType())[i][color == Color.WHITE ? j : 7 - j];
 				}
 		return score;
 	}
@@ -240,9 +352,11 @@ public class Board implements Cloneable {
 				board.boardArr[i][j].board	= board;
 			}
 
-		board.kingPos	= new HashMap<>();
+		board.kingPos = new HashMap<>();
 		board.kingPos.putAll(kingPos);
 
+		board.log = (Log) log.clone();
+
 		return board;
 	}
 

src/dev/kske/chess/board/King.java

@@ -17,7 +17,26 @@ public class King extends Piece {
 
 	@Override
 	public boolean isValidMove(Move move) {
-		return move.xDist <= 1 && move.yDist <= 1 && isFreePath(move);
+		// Castling
+		if (getMoveCounter() == 0 && move.xDist == 2 && move.yDist == 0) {
+
+			// Kingside
+			if (board.getBoardArr()[7][move.pos.y] != null && board.getBoardArr()[7][move.pos.y].getType() == Type.ROOK
+					&& isFreePath(new Move(new Position(5, move.pos.y), new Position(7, move.pos.y)))) {
+				move.type = Move.Type.CASTLING;
+				return true;
+			}
+
+			// Queenside
+			if (board.getBoardArr()[0][move.pos.y] != null && board.getBoardArr()[0][move.pos.y].getType() == Type.ROOK
+					&& isFreePath(new Move(new Position(1, move.pos.y), new Position(4, move.pos.y)))) {
+				move.type = Move.Type.CASTLING;
+				return true;
+			}
+
+		}
+
+		return move.xDist <= 1 && move.yDist <= 1 && checkDestination(move);
 	}
 
 	@Override
@@ -29,9 +48,33 @@ public class King extends Piece {
 					Move move = new Move(pos, new Position(i, j));
 					if (board.getDest(move) == null || board.getDest(move).getColor() != getColor()) moves.add(move);
 				}
+
+		// Castling
+		// TODO: Check attacked squares in between
+		// TODO: Castling out of check?
+		if (getMoveCounter() == 0) {
+
+			// Kingside
+			if (board.getBoardArr()[7][pos.y] != null && board.getBoardArr()[7][pos.y].getType() == Type.ROOK
+					&& isFreePath(new Move(new Position(5, pos.y), new Position(7, pos.y))))
+				moves.add(new Move(pos, new Position(6, pos.y), Move.Type.CASTLING));
+
+			// Queenside
+			if (board.getBoardArr()[0][pos.y] != null && board.getBoardArr()[0][pos.y].getType() == Type.ROOK
+					&& isFreePath(new Move(new Position(1, pos.y), new Position(4, pos.y))))
+				moves.add(new Move(pos, new Position(2, pos.y), Move.Type.CASTLING));
+		}
+
 		return moves;
 	}
 
+	@Override
+	protected boolean isFreePath(Move move) {
+		for (int i = move.pos.x, j = move.pos.y; i != move.dest.x || j != move.dest.y; i += move.xSign, j += move.ySign)
+			if (board.getBoardArr()[i][j] != null) return false;
+		return true;
+	}
+
 	@Override
 	public Type getType() { return Type.KING; }
 }

src/dev/kske/chess/board/Knight.java

@@ -17,7 +17,8 @@ public class Knight extends Piece {
 
 	@Override
 	public boolean isValidMove(Move move) {
-		return Math.abs(move.xDist - move.yDist) == 1 && (move.xDist == 1 || move.yDist == 1) && isFreePath(move);
+		return Math.abs(move.xDist - move.yDist) == 1
+				&& (move.xDist == 1 && move.yDist == 2 || move.xDist == 2 && move.yDist == 1) && checkDestination(move);
 	}
 
 	private void checkAndInsertMove(List<Move> moves, Position pos, int offsetX, int offsetY) {

src/dev/kske/chess/board/Log.java

@@ -0,0 +1,55 @@
+package dev.kske.chess.board;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>Log.java</strong><br>
+ * Created: <strong>09.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class Log implements Cloneable {
+
+	private List<LoggedMove> moves;
+
+	public Log() {
+		moves = new ArrayList<>();
+	}
+
+	public void add(Move move, Piece capturedPiece) {
+		moves.add(new LoggedMove(move, capturedPiece));
+	}
+
+	public LoggedMove getLast() {
+		return moves.get(moves.size() - 1);
+	}
+	
+	public void removeLast() {
+		if (!moves.isEmpty()) moves.remove(moves.size() - 1);
+	}
+
+	@Override
+	public Object clone() {
+		Log log = null;
+		try {
+			log = (Log) super.clone();
+		} catch (CloneNotSupportedException e) {
+			e.printStackTrace();
+		}
+		log.moves = new ArrayList<>();
+		log.moves.addAll(this.moves);
+		return log;
+	}
+
+	public static class LoggedMove {
+
+		public final Move		move;
+		public final Piece	capturedPiece;
+
+		public LoggedMove(Move move, Piece capturedPiece) {
+			this.move		= move;
+			this.capturedPiece	= capturedPiece;
+		}
+	}
+}

src/dev/kske/chess/board/Move.java

@@ -10,16 +10,22 @@ public class Move {
 
 	public final Position	pos, dest;
 	public final int		xDist, yDist, xSign, ySign;
+	public Type				type;
 
-	public Move(Position pos, Position dest) {
+	public Move(Position pos, Position dest, Type type) {
 		this.pos	= pos;
 		this.dest	= dest;
+		this.type	= type;
 		xDist		= Math.abs(dest.x - pos.x);
 		yDist		= Math.abs(dest.y - pos.y);
 		xSign		= (int) Math.signum(dest.x - pos.x);
 		ySign		= (int) Math.signum(dest.y - pos.y);
 	}
 
+	public Move(Position pos, Position dest) {
+		this(pos, dest, Type.NORMAL);
+	}
+
 	public Move(int xPos, int yPos, int xDest, int yDest) {
 		this(new Position(xPos, yPos), new Position(xDest, yDest));
 	}
@@ -34,4 +40,8 @@ public class Move {
 	public String toString() {
 		return String.format("%s -> %s", pos, dest);
 	}
+
+	public static enum Type {
+		NORMAL, PAWN_PROMOTION, CASTLING, EN_PASSANT, UNKNOWN
+	}
 }

src/dev/kske/chess/board/Pawn.java

@@ -17,12 +17,17 @@ public class Pawn extends Piece {
 
 	@Override
 	public boolean isValidMove(Move move) {
-		// TODO: en passant, pawn promotion
+		// TODO: en passant
 		boolean	step		= move.isVertical() && move.yDist == 1;
 		boolean	doubleStep	= move.isVertical() && move.yDist == 2;
 		boolean	strafe		= move.isDiagonal() && move.xDist == 1;
 		if (getColor() == Color.WHITE) doubleStep &= move.pos.y == 6;
 		else doubleStep &= move.pos.y == 1;
+
+		// Mark move as pawn promotion if necessary
+		if (move.ySign == 1 && move.pos.y == 6 || move.ySign == -1 && move.pos.y == 1)
+			move.type = Move.Type.PAWN_PROMOTION;
+
 		return (step ^ doubleStep ^ strafe) && move.ySign == (getColor() == Color.WHITE ? -1 : 1) && isFreePath(move);
 	}
 
@@ -43,8 +48,6 @@ public class Pawn extends Piece {
 
 		int sign = getColor() == Color.WHITE ? -1 : 1;
 
-		if (sign == -1 && pos.y == 1 || sign == 1 && pos.y == 7) return moves;
-
 		// Strafe left
 		if (pos.x > 0) {
 			Move move = new Move(pos, new Position(pos.x - 1, pos.y + sign));
@@ -68,6 +71,11 @@ public class Pawn extends Piece {
 			Move move = new Move(pos, new Position(pos.x, pos.y + 2 * sign));
 			if (isFreePath(move)) moves.add(move);
 		}
+
+		// Mark moves as pawn promotions if necessary
+		if (sign == 1 && pos.y == 6 || sign == -1 && pos.y == 1)
+			moves.parallelStream().forEach(m -> m.type = Move.Type.PAWN_PROMOTION);
+
 		return moves;
 	}
 

src/dev/kske/chess/board/Piece.java

@@ -11,8 +11,9 @@ import java.util.List;
  */
 public abstract class Piece implements Cloneable {
 
-	protected Color	color;
-	protected Board	board;
+	private final Color	color;
+	protected Board		board;
+	private int			moveCounter;
 
 	public Piece(Color color, Board board) {
 		this.color	= color;
@@ -22,11 +23,10 @@ public abstract class Piece implements Cloneable {
 	public List<Move> getMoves(Position pos) {
 		List<Move> moves = getPseudolegalMoves(pos);
 		for (Iterator<Move> iterator = moves.iterator(); iterator.hasNext();) {
-			Move	move			= iterator.next();
-			Piece	capturePiece	= board.move(move);
-			if (board.checkCheck(getColor()))
-				iterator.remove();
-			board.revert(move, capturePiece);
+			Move move = iterator.next();
+			board.move(move);
+			if (board.checkCheck(getColor())) iterator.remove();
+			board.revert();
 		}
 		return moves;
 	}
@@ -66,8 +66,18 @@ public abstract class Piece implements Cloneable {
 
 	public Color getColor() { return color; }
 
+	public int getMoveCounter() { return moveCounter; }
+
+	public void incMoveCounter() {
+		++moveCounter;
+	}
+
+	public void decMoveCounter() {
+		--moveCounter;
+	}
+
 	public static enum Type {
-		KING, QUEEN, ROOK, KNIGHT, BISHOP, PAWN;
+		KING, QUEEN, ROOK, KNIGHT, BISHOP, PAWN
 	}
 
 	public static enum Color {

src/dev/kske/chess/game/Game.java

@@ -1,12 +1,16 @@
 package dev.kske.chess.game;
 
+import java.util.HashMap;
 import java.util.Map;
 
 import dev.kske.chess.board.Board;
 import dev.kske.chess.board.GameState;
 import dev.kske.chess.board.Move;
 import dev.kske.chess.board.Piece.Color;
+import dev.kske.chess.game.ai.AIPlayer;
 import dev.kske.chess.ui.BoardComponent;
+import dev.kske.chess.ui.BoardPane;
+import dev.kske.chess.ui.OverlayComponent;
 
 /**
  * Project: <strong>Chess</strong><br>
@@ -18,19 +22,44 @@ public class Game {
 
 	private Map<Color, Player>	players;
 	private Board				board;
+	private OverlayComponent	overlayComponent;
 	private BoardComponent		boardComponent;
 
-	public Game(Map<Color, Player> players, BoardComponent boardComponent) {
-		this.players		= players;
-		this.boardComponent	= boardComponent;
-		this.board			= boardComponent.getBoard();
+	public Game(Map<Color, Player> players, BoardPane boardPane) {
+		this.players			= players;
+		this.overlayComponent	= boardPane.getOverlayComponent();
+		this.boardComponent		= boardPane.getBoardComponent();
+		this.board				= new Board();
+		boardComponent.setBoard(board);
 
 		// Initialize the game variable in each player
 		players.values().forEach(player -> player.setGame(this));
 	}
 
-	public void start() {
-		players.get(Color.WHITE).requestMove();
+	public static Game createNatural(BoardPane boardPane) {
+		Map<Color, Player>	players	= new HashMap<>();
+		OverlayComponent	overlay	= boardPane.getOverlayComponent();
+
+		players.put(Color.WHITE, new NaturalPlayer(Color.WHITE, overlay));
+		players.put(Color.BLACK, new NaturalPlayer(Color.BLACK, overlay));
+		return new Game(players, boardPane);
+	}
+
+	public static Game createNaturalVsAI(BoardPane boardPane, int maxDepth, int alphaBeta) {
+		Map<Color, Player>	players	= new HashMap<>();
+		OverlayComponent	overlay	= boardPane.getOverlayComponent();
+
+		players.put(Color.WHITE, new NaturalPlayer(Color.WHITE, overlay));
+		players.put(Color.BLACK, new AIPlayer(Color.BLACK, maxDepth, alphaBeta));
+		return new Game(players, boardPane);
+	}
+
+	public static Game createAIVsAI(BoardPane boardPane, int maxDepthW, int maxDepthB, int alphaBetaW, int alphaBetaB) {
+		Map<Color, Player> players = new HashMap<>();
+
+		players.put(Color.WHITE, new AIPlayer(Color.WHITE, maxDepthW, alphaBetaW));
+		players.put(Color.BLACK, new AIPlayer(Color.BLACK, maxDepthB, alphaBetaB));
+		return new Game(players, boardPane);
 	}
 
 	public void onMove(Player player, Move move) {
@@ -47,8 +76,29 @@ public class Game {
 				default:
 					boardComponent.repaint();
 					players.get(player.color.opposite()).requestMove();
-
 			}
+			overlayComponent.displayArrow(move);
 		} else player.requestMove();
 	}
+
+	public void start() {
+		players.get(Color.WHITE).requestMove();
+	}
+
+	public void reset() {
+		players.forEach((k, v) -> v.cancelMove());
+		board.initializeDefaultPositions();
+		boardComponent.repaint();
+		overlayComponent.clearDots();
+		overlayComponent.clearArrow();
+	}
+
+	/**
+	 * Removed all connections between the game and the ui.
+	 */
+	public void disconnect() {
+		players.values().forEach(Player::disconnect);
+	}
+
+	public Board getBoard() { return board; }
 }

src/dev/kske/chess/game/NaturalPlayer.java

@@ -1,12 +1,13 @@
 package dev.kske.chess.game;
 
-import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
+import java.awt.event.MouseListener;
 import java.util.List;
 import java.util.stream.Collectors;
 
 import dev.kske.chess.board.Board;
 import dev.kske.chess.board.Move;
+import dev.kske.chess.board.Move.Type;
 import dev.kske.chess.board.Piece.Color;
 import dev.kske.chess.board.Position;
 import dev.kske.chess.ui.OverlayComponent;
@@ -17,47 +18,71 @@ import dev.kske.chess.ui.OverlayComponent;
  * Created: <strong>06.07.2019</strong><br>
  * Author: <strong>Kai S. K. Engelbart</strong>
  */
-public class NaturalPlayer extends Player {
+public class NaturalPlayer extends Player implements MouseListener {
 
-	private boolean moveRequested;
+	private final OverlayComponent overlayComponent;
 
-	public NaturalPlayer(Board board, Color color, OverlayComponent overlayComponent) {
-		super(board, color);
-		moveRequested = false;
-		overlayComponent.addMouseListener(new MouseAdapter() {
+	private boolean		moveRequested;
+	private Position	pos;
 
-			private Position pos;
+	public NaturalPlayer(Color color, OverlayComponent overlayComponent) {
+		super(color);
+		this.overlayComponent	= overlayComponent;
+		moveRequested			= false;
 
-			@Override
-			public void mousePressed(MouseEvent evt) {
-				if (!moveRequested) return;
-				if (pos == null) {
-					pos = new Position(evt.getPoint().x / overlayComponent.getTileSize(),
-							evt.getPoint().y / overlayComponent.getTileSize());
-
-					Board board = (Board) NaturalPlayer.this.board.clone();
-					if (board.get(pos) != null && board.get(pos).getColor() == color) {
-						List<Position> positions = board.getMoves(pos)
-							.stream()
-							.map(move -> move.dest)
-							.collect(Collectors.toList());
-						overlayComponent.displayDots(positions);
-					} else pos = null;
-				} else {
-					Position dest = new Position(evt.getPoint().x / overlayComponent.getTileSize(),
-							evt.getPoint().y / overlayComponent.getTileSize());
-
-					overlayComponent.clearDots();
-					moveRequested = false;
-					game.onMove(NaturalPlayer.this, new Move(pos, dest));
-					pos = null;
-				}
-			}
-		});
+		overlayComponent.addMouseListener(this);
 	}
 
 	@Override
 	public void requestMove() {
 		moveRequested = true;
 	}
+
+	@Override
+	public void cancelMove() {
+		moveRequested = false;
+	}
+
+	@Override
+	public void disconnect() {
+		overlayComponent.removeMouseListener(this);
+	}
+
+	@Override
+	public void mousePressed(MouseEvent evt) {
+		if (!moveRequested) return;
+		if (pos == null) {
+			pos = new Position(evt.getPoint().x / overlayComponent.getTileSize(),
+					evt.getPoint().y / overlayComponent.getTileSize());
+
+			Board board = (Board) NaturalPlayer.this.board.clone();
+			if (board.get(pos) != null && board.get(pos).getColor() == color) {
+				List<Position> positions = board.getMoves(pos)
+					.stream()
+					.map(move -> move.dest)
+					.collect(Collectors.toList());
+				overlayComponent.displayDots(positions);
+			} else pos = null;
+		} else {
+			Position dest = new Position(evt.getPoint().x / overlayComponent.getTileSize(),
+					evt.getPoint().y / overlayComponent.getTileSize());
+
+			overlayComponent.clearDots();
+			moveRequested = false;
+			game.onMove(NaturalPlayer.this, new Move(pos, dest, Type.UNKNOWN));
+			pos = null;
+		}
+	}
+
+	@Override
+	public void mouseClicked(MouseEvent e) {}
+
+	@Override
+	public void mouseReleased(MouseEvent e) {}
+
+	@Override
+	public void mouseEntered(MouseEvent e) {}
+
+	@Override
+	public void mouseExited(MouseEvent e) {}
 }

src/dev/kske/chess/game/Player.java

@@ -15,16 +15,22 @@ public abstract class Player {
 	protected Board	board;
 	protected Color	color;
 
-	public Player(Board board, Color color) {
-		this.board	= board;
-		this.color	= color;
+	public Player(Color color) {
+		this.color = color;
 	}
 
 	public abstract void requestMove();
 
+	public abstract void cancelMove();
+
+	public abstract void disconnect();
+
 	public Game getGame() { return game; }
 
-	public void setGame(Game game) { this.game = game; }
+	public void setGame(Game game) {
+		this.game	= game;
+		board		= game.getBoard();
+	}
 
 	public Board getBoard() { return board; }
 

src/dev/kske/chess/game/ai/AIPlayer.java

@@ -6,6 +6,7 @@ import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
 
 import javax.swing.SwingUtilities;
 
@@ -24,15 +25,22 @@ public class AIPlayer extends Player {
 
 	private int	availableProcessors;
 	private int	maxDepth;
+	private int	alphaBetaThreshold;
 
-	public AIPlayer(Board board, Color color, int maxDepth) {
-		super(board, color);
-		availableProcessors	= Runtime.getRuntime().availableProcessors();
-		this.maxDepth		= maxDepth;
+	private volatile boolean			exitRequested;
+	private volatile ExecutorService	executor;
+
+	public AIPlayer(Color color, int maxDepth, int alphaBetaThreshold) {
+		super(color);
+		availableProcessors		= Runtime.getRuntime().availableProcessors();
+		this.maxDepth			= maxDepth;
+		this.alphaBetaThreshold	= alphaBetaThreshold;
+		exitRequested			= false;
 	}
 
 	@Override
 	public void requestMove() {
+		exitRequested = false;
 		/*
 		 * Define some processing threads, split the available moves between them and
 		 * retrieve the result after their execution.
@@ -41,8 +49,8 @@ public class AIPlayer extends Player {
 			/*
 			 * Get a copy of the board and the available moves.
 			 */
-			Board				board		= (Board) AIPlayer.this.board.clone();
-			List<Move>			moves		= board.getMoves(color);
+			Board		board	= (Board) AIPlayer.this.board.clone();
+			List<Move>	moves	= board.getMoves(color);
 
 			/*
 			 * Define move processors and split the available moves between them.
@@ -55,16 +63,16 @@ public class AIPlayer extends Player {
 			for (int i = 0; i < numThreads; i++) {
 				if (rem-- > 0) ++endIndex;
 				endIndex += step;
-				processors.add(
-						new MoveProcessor((Board) board.clone(), moves.subList(beginIndex, endIndex), color, maxDepth));
+				processors.add(new MoveProcessor((Board) board.clone(), moves.subList(beginIndex, endIndex), color,
+						maxDepth, alphaBetaThreshold));
 				beginIndex = endIndex;
 			}
 
 			/*
 			 * Execute processors, get the best result and pass it back to the Game class
 			 */
-			ExecutorService			executor	= Executors.newFixedThreadPool(numThreads);
-			List<ProcessingResult>	results		= new ArrayList<>(numThreads);
+			executor = Executors.newFixedThreadPool(numThreads);
+			List<ProcessingResult> results = new ArrayList<>(numThreads);
 			try {
 				List<Future<ProcessingResult>> futures = executor.invokeAll(processors);
 				for (Future<ProcessingResult> f : futures)
@@ -74,7 +82,23 @@ public class AIPlayer extends Player {
 				ex.printStackTrace();
 			}
 			results.sort((r1, r2) -> Integer.compare(r2.score, r1.score));
-			SwingUtilities.invokeLater(() -> game.onMove(this, results.get(0).move));
+			if (!exitRequested) SwingUtilities.invokeLater(() -> game.onMove(this, results.get(0).move));
 		}, "AIPlayer calculation setup").start();
 	}
+
+	@Override
+	public void cancelMove() {
+		exitRequested = true;
+		if (executor != null) {
+			executor.shutdownNow();
+			try {
+				executor.awaitTermination(500, TimeUnit.MILLISECONDS);
+			} catch (InterruptedException e) {
+				e.printStackTrace();
+			}
+		}
+	}
+
+	@Override
+	public void disconnect() {}
 }

src/dev/kske/chess/game/ai/MoveProcessor.java

@@ -5,7 +5,6 @@ import java.util.concurrent.Callable;
 
 import dev.kske.chess.board.Board;
 import dev.kske.chess.board.Move;
-import dev.kske.chess.board.Piece;
 import dev.kske.chess.board.Piece.Color;
 
 /**
@@ -17,17 +16,19 @@ import dev.kske.chess.board.Piece.Color;
 public class MoveProcessor implements Callable<ProcessingResult> {
 
 	private final Board			board;
-	private final List<Move>	rootMoves;;
+	private final List<Move>	rootMoves;
 	private final Color			color;
 	private final int			maxDepth;
+	private final int			alphaBetaThreshold;
 
 	private Move bestMove;
 
-	public MoveProcessor(Board board, List<Move> rootMoves, Color color, int maxDepth) {
+	public MoveProcessor(Board board, List<Move> rootMoves, Color color, int maxDepth, int alphaBetaThreshold) {
 		this.board		= board;
 		this.rootMoves	= rootMoves;
 		this.color		= color;
 		this.maxDepth	= maxDepth;
+		this.alphaBetaThreshold	= alphaBetaThreshold;
 	}
 
 	@Override
@@ -39,12 +40,12 @@ public class MoveProcessor implements Callable<ProcessingResult> {
 	private int miniMax(Board board, List<Move> moves, Color color, int depth) {
 		int bestValue = Integer.MIN_VALUE;
 		for (Move move : moves) {
-			Piece	capturePiece	= board.move(move);
+			board.move(move);
 			int		teamValue		= board.evaluate(color);
 			int		enemyValue		= board.evaluate(color.opposite());
 			int		valueChange		= teamValue - enemyValue;
 
-			if (depth < maxDepth && valueChange >= 0)
+			if (depth < maxDepth && valueChange >= alphaBetaThreshold)
 				valueChange -= miniMax(board, board.getMoves(color.opposite()), color.opposite(), depth + 1);
 
 			if (valueChange > bestValue) {
@@ -52,7 +53,7 @@ public class MoveProcessor implements Callable<ProcessingResult> {
 				if (depth == 0) bestMove = move;
 			}
 
-			board.revert(move, capturePiece);
+			board.revert();
 		}
 		return bestValue;
 	}

src/dev/kske/chess/ui/AIConfigDialog.java

@@ -0,0 +1,82 @@
+package dev.kske.chess.ui;
+
+import java.awt.Dimension;
+
+import javax.swing.JButton;
+import javax.swing.JDialog;
+import javax.swing.JLabel;
+import javax.swing.JSpinner;
+import javax.swing.SpinnerNumberModel;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>AIConfigDialog.java</strong><br>
+ * Created: <strong>16.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class AIConfigDialog extends JDialog {
+
+	private static final long serialVersionUID = -8047984368152479992L;
+
+	private int		maxDepth;
+	private int		alphaBetaThreshold;
+	private boolean	startGame	= false;
+
+	public AIConfigDialog() {
+		setSize(new Dimension(337, 212));
+		setModal(true);
+		setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
+		setTitle("AI Configuration");
+		getContentPane().setLayout(null);
+
+		JSpinner spAlphaBetaThreshold = new JSpinner();
+		spAlphaBetaThreshold.setBounds(222, 68, 95, 28);
+		getContentPane().add(spAlphaBetaThreshold);
+		spAlphaBetaThreshold.setModel(new SpinnerNumberModel(-10, -100, 100, 5));
+
+		JSpinner spMaxDepth = new JSpinner();
+		spMaxDepth.setBounds(222, 6, 95, 28);
+		getContentPane().add(spMaxDepth);
+		spMaxDepth.setModel(new SpinnerNumberModel(4, 1, 10, 1));
+
+		JLabel lblAlphabetaThreshold = new JLabel("Alpha-Beta Threshold:");
+		lblAlphabetaThreshold.setBounds(16, 68, 194, 28);
+		getContentPane().add(lblAlphabetaThreshold);
+
+		JButton btnOk = new JButton("OK");
+		btnOk.setBounds(16, 137, 84, 28);
+		getContentPane().add(btnOk);
+		btnOk.addActionListener((evt) -> {
+			maxDepth			= ((Integer) spMaxDepth.getValue()).intValue();
+			alphaBetaThreshold	= ((Integer) spAlphaBetaThreshold.getValue()).intValue();
+			startGame			= true;
+			dispose();
+		});
+		btnOk.setToolTipText("Start the game");
+
+		JButton btnCancel = new JButton("Cancel");
+		btnCancel.setBounds(222, 137, 95, 28);
+		getContentPane().add(btnCancel);
+		btnCancel.addActionListener((evt) -> dispose());
+		btnCancel.setToolTipText("Cancel the game start");
+
+		JLabel lblMaximalRecursionDepth = new JLabel("Maximal Recursion Depth:");
+		lblMaximalRecursionDepth.setBounds(16, 12, 194, 16);
+		getContentPane().add(lblMaximalRecursionDepth);
+
+		setLocationRelativeTo(null);
+	}
+
+	public int getMaxDepth() { return maxDepth; }
+
+	public void setMaxDepth(int maxDepth) { this.maxDepth = maxDepth; }
+
+	public int getAlphaBetaThreshold() { return alphaBetaThreshold; }
+
+	public void setAlphaBetaThreshold(int alphaBetaThreshold) { this.alphaBetaThreshold = alphaBetaThreshold; }
+
+	public boolean isStartGame() { return startGame; }
+
+	public void setStartGame(boolean startGame) { this.startGame = startGame; }
+
+}

src/dev/kske/chess/ui/GameModeDialog.java

@@ -1,72 +0,0 @@
-package dev.kske.chess.ui;
-
-import java.awt.FlowLayout;
-import java.util.HashMap;
-import java.util.Map;
-
-import javax.swing.JButton;
-import javax.swing.JDialog;
-
-import dev.kske.chess.board.Board;
-import dev.kske.chess.board.Piece.Color;
-import dev.kske.chess.game.Game;
-import dev.kske.chess.game.NaturalPlayer;
-import dev.kske.chess.game.Player;
-import dev.kske.chess.game.ai.AIPlayer;
-
-/**
- * Project: <strong>Chess</strong><br>
- * File: <strong>GameModeDialog.java</strong><br>
- * Created: <strong>06.07.2019</strong><br>
- * Author: <strong>Kai S. K. Engelbart</strong>
- */
-public class GameModeDialog extends JDialog {
-
-	private static final long serialVersionUID = 5470026233924735607L;
-
-	/**
-	 * Create the dialog.
-	 */
-	public GameModeDialog(BoardPane boardPane) {
-		super();
-		setModal(true);
-		setTitle("Game Mode Selection");
-		setBounds(100, 100, 231, 133);
-		setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
-		getContentPane().setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));
-
-		final BoardComponent	boardComponent		= boardPane.getBoardComponent();
-		final OverlayComponent	overlayComponent	= boardPane.getOverlayComponent();
-		final Board				board				= boardComponent.getBoard();
-
-		JButton btnNatural = new JButton("Game against natural opponent");
-		btnNatural.addActionListener((evt) -> {
-			Map<Color, Player> players = new HashMap<>();
-			players.put(Color.WHITE, new NaturalPlayer(board, Color.WHITE, overlayComponent));
-			players.put(Color.BLACK, new NaturalPlayer(board, Color.BLACK, overlayComponent));
-			new Game(players, boardComponent).start();
-			dispose();
-		});
-		getContentPane().add(btnNatural);
-
-		JButton btnAI = new JButton("Game against AI");
-		btnAI.addActionListener((evt) -> {
-			Map<Color, Player> players = new HashMap<>();
-			players.put(Color.WHITE, new NaturalPlayer(board, Color.WHITE, overlayComponent));
-			players.put(Color.BLACK, new AIPlayer(board, Color.BLACK, 4));
-			new Game(players, boardComponent).start();
-			dispose();
-		});
-		getContentPane().add(btnAI);
-
-		JButton btnAI2 = new JButton("AI against AI");
-		btnAI2.addActionListener((evt) -> {
-			Map<Color, Player> players = new HashMap<>();
-			players.put(Color.WHITE, new AIPlayer(board, Color.WHITE, 4));
-			players.put(Color.BLACK, new AIPlayer(board, Color.BLACK, 3));
-			new Game(players, boardComponent).start();
-			dispose();
-		});
-		getContentPane().add(btnAI2);
-	}
-}

src/dev/kske/chess/ui/MainWindow.java

@@ -2,13 +2,13 @@ package dev.kske.chess.ui;
 
 import java.awt.BorderLayout;
 import java.awt.EventQueue;
+import java.awt.Toolkit;
 
 import javax.swing.JButton;
 import javax.swing.JFrame;
 import javax.swing.JPanel;
 
-import dev.kske.chess.board.Board;
-
+import dev.kske.chess.game.Game;
 
 /**
  * Project: <strong>Chess</strong><br>
@@ -18,7 +18,9 @@ import dev.kske.chess.board.Board;
  */
 public class MainWindow {
 
-	private JFrame mframe;
+	private JFrame		mframe;
+	private BoardPane	boardPane;
+	private Game		game;
 
 	/**
 	 * Launch the application.
@@ -53,19 +55,26 @@ public class MainWindow {
 		mframe.setBounds(100, 100, 494, 565);
 		mframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
-		BoardPane boardPane = new BoardPane();
-		boardPane.getBoardComponent().setBoard(new Board());
+		mframe.setIconImage(Toolkit.getDefaultToolkit().getImage(getClass().getResource("/pieces/king_white.png")));
+
+		boardPane = new BoardPane();
 		mframe.getContentPane().add(boardPane, BorderLayout.CENTER);
 
+		mframe.setJMenuBar(new MenuBar(this));
+
 		JPanel toolPanel = new JPanel();
 		mframe.getContentPane().add(toolPanel, BorderLayout.NORTH);
 
 		JButton btnRestart = new JButton("Restart");
-		btnRestart.addActionListener((evt) -> System.err.println("Resetting not implemented!"));
+		btnRestart.addActionListener((evt) -> { if (game != null) game.reset(); game.start(); });
 		toolPanel.add(btnRestart);
 		mframe.pack();
-
-		// Display dialog for game mode selection
-		new GameModeDialog(boardPane).setVisible(true);
+		mframe.setLocationRelativeTo(null);
 	}
+
+	public BoardPane getBoardPane() { return boardPane; }
+
+	public Game getGame() { return game; }
+
+	public void setGame(Game game) { this.game = game; }
 }

src/dev/kske/chess/ui/MenuBar.java

@@ -0,0 +1,64 @@
+package dev.kske.chess.ui;
+
+import javax.swing.JMenu;
+import javax.swing.JMenuBar;
+import javax.swing.JMenuItem;
+
+import dev.kske.chess.game.Game;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>MenuBar.java</strong><br>
+ * Created: <strong>16.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class MenuBar extends JMenuBar {
+
+	private static final long serialVersionUID = -7221583703531248228L;
+
+	private final MainWindow	mainWindow;
+	private final BoardPane		boardPane;
+
+	public MenuBar(MainWindow mainWindow) {
+		this.mainWindow	= mainWindow;
+		boardPane		= mainWindow.getBoardPane();
+
+		initGameMenu();
+	}
+
+	private void initGameMenu() {
+		JMenu gameMenu = new JMenu("Game");
+
+		JMenuItem	naturalMenuItem	= new JMenuItem("Game against natural opponent");
+		JMenuItem	aiMenuItem		= new JMenuItem("Game against artificial opponent");
+		JMenuItem	aiVsAiMenuItem	= new JMenuItem("Watch AI vs. AI");
+
+		naturalMenuItem.addActionListener((evt) -> startGame(Game.createNatural(boardPane)));
+
+		aiMenuItem.addActionListener((evt) -> {
+			AIConfigDialog dialog = new AIConfigDialog();
+			dialog.setVisible(true);
+			if (dialog.isStartGame())
+				startGame(Game.createNaturalVsAI(boardPane, dialog.getMaxDepth(), dialog.getAlphaBetaThreshold()));
+		});
+
+		aiVsAiMenuItem.addActionListener((evt) -> startGame(Game.createAIVsAI(boardPane, 4, 3, -10, -10)));
+
+		gameMenu.add(naturalMenuItem);
+		gameMenu.add(aiMenuItem);
+		gameMenu.add(aiVsAiMenuItem);
+
+		add(gameMenu);
+
+		// Start a game
+		naturalMenuItem.doClick();
+	}
+
+	private void startGame(Game game) {
+		mainWindow.setGame(game);
+
+		// Update board and board component
+		game.reset();
+		game.start();
+	}
+}

src/dev/kske/chess/ui/OverlayComponent.java

@@ -2,11 +2,17 @@ package dev.kske.chess.ui;
 
 import java.awt.Color;
 import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.awt.Point;
+import java.awt.Polygon;
+import java.awt.Shape;
+import java.awt.geom.AffineTransform;
 import java.util.ArrayList;
 import java.util.List;
 
 import javax.swing.JComponent;
 
+import dev.kske.chess.board.Move;
 import dev.kske.chess.board.Position;
 
 /**
@@ -22,11 +28,12 @@ public class OverlayComponent extends JComponent {
 	private final BoardPane boardPane;
 
 	private List<Position>	dots;
+	private Move			arrow;
 
 	public OverlayComponent(BoardPane boardPane) {
 		this.boardPane = boardPane;
 		setSize(boardPane.getPreferredSize());
-		dots			= new ArrayList<>();
+		dots = new ArrayList<>();
 	}
 
 	@Override
@@ -34,7 +41,7 @@ public class OverlayComponent extends JComponent {
 		super.paintComponent(g);
 
 		final int tileSize = getTileSize();
-		
+
 		// Draw possible moves if a piece was selected
 		if (!dots.isEmpty()) {
 			g.setColor(Color.green);
@@ -45,6 +52,43 @@ public class OverlayComponent extends JComponent {
 						radius,
 						radius);
 		}
+
+		if (arrow != null) {
+			g.setColor(new Color(255, 0, 0, 127));
+			Point	pos		= new Point(arrow.pos.x * tileSize + tileSize / 2, arrow.pos.y * tileSize + tileSize / 2);
+			Point	dest	= new Point(arrow.dest.x * tileSize + tileSize / 2, arrow.dest.y * tileSize + tileSize / 2);
+			((Graphics2D) g).fill(createArrowShape(pos, dest));
+		}
+	}
+
+	private Shape createArrowShape(Point pos, Point dest) {
+		Polygon arrowPolygon = new Polygon();
+		arrowPolygon.addPoint(-6, 1);
+		arrowPolygon.addPoint(3, 1);
+		arrowPolygon.addPoint(3, 3);
+		arrowPolygon.addPoint(6, 0);
+		arrowPolygon.addPoint(3, -3);
+		arrowPolygon.addPoint(3, -1);
+		arrowPolygon.addPoint(-6, -1);
+
+		Point midPoint = midpoint(pos, dest);
+
+		double	rotate		= Math.atan2(dest.y - pos.y, dest.x - pos.x);
+		double	ptDistance	= pos.distance(dest);
+		double	scale		= ptDistance / 12.0;							// 12 because it's the length of the arrow
+																			// polygon.
+
+		AffineTransform transform = new AffineTransform();
+
+		transform.translate(midPoint.x, midPoint.y);
+		transform.rotate(rotate);
+		transform.scale(scale, 5);
+
+		return transform.createTransformedShape(arrowPolygon);
+	}
+
+	private Point midpoint(Point p1, Point p2) {
+		return new Point((int) ((p1.x + p2.x) / 2.0), (int) ((p1.y + p2.y) / 2.0));
 	}
 
 	public void displayDots(List<Position> dots) {
@@ -58,5 +102,15 @@ public class OverlayComponent extends JComponent {
 		repaint();
 	}
 
+	public void displayArrow(Move arrow) {
+		this.arrow = arrow;
+		repaint();
+	}
+
+	public void clearArrow() {
+		arrow = null;
+		repaint();
+	}
+
 	public int getTileSize() { return boardPane.getTileSize(); }
 }

src/dev/kske/chess/ui/TextureUtil.java

@@ -2,8 +2,8 @@ package dev.kske.chess.ui;
 
 import java.awt.Image;
 import java.awt.image.BufferedImage;
-import java.io.File;
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -19,11 +19,13 @@ import dev.kske.chess.board.Piece;
  */
 public class TextureUtil {
 
-	private static Map<String, Image> textures;
+	private static Map<String, Image> textures, scaledTextures;
 
 	static {
 		textures = new HashMap<>();
+		scaledTextures	= new HashMap<>();
 		loadPieceTextures();
+		scaledTextures.putAll(textures);
 	}
 
 	private TextureUtil() {}
@@ -36,26 +38,28 @@ public class TextureUtil {
 	 */
 	public static Image getPieceTexture(Piece piece) {
 		String key = piece.getType().toString().toLowerCase() + "_" + piece.getColor().toString().toLowerCase();
-		return textures.get(key);
+		return scaledTextures.get(key);
 	}
 
 	/**
 	 * Scales all piece textures to fit the current tile size
 	 */
 	public static void scalePieceTextures(int scale) {
-		textures.replaceAll((key, img) -> img.getScaledInstance(scale, scale, Image.SCALE_SMOOTH));
+		scaledTextures.clear();
+		textures
+			.forEach((key, img) -> scaledTextures.put(key, img.getScaledInstance(scale, scale, Image.SCALE_SMOOTH)));
 	}
 
 	/**
-	 * Loads an image from a file.
+	 * Loads an image from a file in the resource folder.
 	 * 
-	 * @param file The image file
+	 * @param fileName The name of the image resource
 	 * @return The loaded image
 	 */
-	private static Image loadImage(File file) {
+	private static Image loadImage(String fileName) {
 		BufferedImage in = null;
 		try {
-			in = ImageIO.read(file);
+			in = ImageIO.read(TextureUtil.class.getResourceAsStream(fileName));
 		} catch (IOException e) {
 			e.printStackTrace();
 		}
@@ -67,10 +71,20 @@ public class TextureUtil {
 	 * The filenames without extensions are used as keys in the map textures.
 	 */
 	private static void loadPieceTextures() {
-		File	dir		= new File("res/pieces");
-		File[]	files	= dir.listFiles((File parentDir, String name) -> name.toLowerCase().endsWith(".png"));
-		for (File file : files)
-			textures.put(file.getName().replaceFirst("[.][^.]+$", ""), TextureUtil.loadImage(file));
+		Arrays
+			.asList("king_white",
+					"king_black",
+					"queen_white",
+					"queen_black",
+					"rook_white",
+					"rook_black",
+					"knight_white",
+					"knight_black",
+					"bishop_white",
+					"bishop_black",
+					"pawn_white",
+					"pawn_black")
+			.forEach(name -> textures.put(name, loadImage("/pieces/" + name + ".png")));
 	}
 
 }

test/dev/kske/chess/test/BoardTest.java

@@ -12,11 +12,11 @@ import dev.kske.chess.board.Queen;
 
 /**
  * Project: <strong>Chess</strong><br>
- * File: <strong>BoardCloneTest.java</strong><br>
+ * File: <strong>BoardTest.java</strong><br>
  * Created: <strong>08.07.2019</strong><br>
  * Author: <strong>Kai S. K. Engelbart</strong>
  */
-class BoardCloneTest {
+class BoardTest {
 
 	Board board;
 
@@ -40,5 +40,4 @@ class BoardCloneTest {
 		clone.getBoardArr()[0][0] = new Queen(Color.BLACK, clone);
 		assertNotEquals(clone.getBoardArr()[0][0], board.getBoardArr()[0][0]);
 	}
-
 }