Fixed memory leak, improved copy constructors

- Changed unit test package structure to match src
- Refactored PositionTest
+ TestToString method in PositionTest

.classpath

@@ -7,11 +7,7 @@
 			<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="con" path="org.eclipse.jdt.junit.JUNIT_CONTAINER/5"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8"/>
 	<classpathentry kind="output" path="bin"/>
 </classpath>

.gitignore

@@ -22,3 +22,4 @@ local.properties
 
 # Annotation Processing
 .apt_generated/
+/engine_infos.ser

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

@@ -20,14 +20,6 @@ public class Bishop extends Piece {
 		return move.isDiagonal() && isFreePath(move);
 	}
 
-	@Override
-	protected boolean isFreePath(Move move) {
-		for (int i = move.pos.x + move.xSign, j = move.pos.y
-				+ move.ySign; i != move.dest.x; i += move.xSign, j += move.ySign)
-			if (board.getBoardArr()[i][j] != null) return false;
-		return checkDestination(move);
-	}
-
 	@Override
 	protected List<Move> getPseudolegalMoves(Position pos) {
 		List<Move> moves = new ArrayList<>();

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

@@ -5,7 +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.Log.MoveNode;
 import dev.kske.chess.board.Piece.Color;
 import dev.kske.chess.board.Piece.Type;
 
@@ -15,11 +15,12 @@ import dev.kske.chess.board.Piece.Type;
  * Created: <strong>01.07.2019</strong><br>
  * Author: <strong>Kai S. K. Engelbart</strong>
  */
-public class Board implements Cloneable {
+public class Board {
 
-	private Piece[][]				boardArr;
+	private Piece[][]						boardArr		= new Piece[8][8];
-	private Map<Color, Position>	kingPos;
+	private Map<Color, Position>			kingPos			= new HashMap<>();
-	private Log						log;
+	private Map<Color, Map<Type, Boolean>>	castlingRights	= new HashMap<>();
+	private Log								log				= new Log();
 
 	private static final Map<Type, int[][]> positionScores;
 
@@ -58,11 +59,44 @@ public class Board implements Cloneable {
 						new int[] { 0, 1, 1, -2, -2, 1, 1, 0 }, new int[] { 0, 0, 0, 0, 0, 0, 0, 0 } });
 	}
 
+	/**
+	 * Initializes the board with the default chess starting position.
+	 */
 	public Board() {
-		boardArr	= new Piece[8][8];
+		initDefaultPositions();
-		kingPos		= new HashMap<>();
+	}
-		log			= new Log();
+
-		initializeDefaultPositions();
+	/**
+	 * Initializes the board with data from a FEN-string.
+	 * 
+	 * @param fen The FEN-string to initialize the board from
+	 */
+	public Board(String fen) {
+		initFromFEN(fen);
+	}
+
+	/**
+	 * Creates a copy of another {@link Board} instance.<br>
+	 * The created object is a deep copy, but does not contain any move history
+	 * apart from the current {@link MoveNode}.
+	 * 
+	 * @param other The {@link Board} instance to copy
+	 */
+	public Board(Board other) {
+		boardArr = new Piece[8][8];
+		for (int i = 0; i < 8; i++)
+			for (int j = 0; j < 8; j++) {
+				if (other.boardArr[i][j] == null) continue;
+				boardArr[i][j]			= (Piece) other.boardArr[i][j].clone();
+				boardArr[i][j].board	= this;
+			}
+
+		kingPos.putAll(other.kingPos);
+		Map<Type, Boolean> whiteCastling = new HashMap<>(other.castlingRights.get(Color.WHITE)),
+				blackCastling = new HashMap<>(other.castlingRights.get(Color.BLACK));
+		castlingRights.put(Color.WHITE, whiteCastling);
+		castlingRights.put(Color.BLACK, blackCastling);
+		log = new Log(other.log, false);
 	}
 
 	/**
@@ -95,7 +129,6 @@ public class Board implements Cloneable {
 	 * Moves a piece across the board without checking if the move is legal.
 	 * 
 	 * @param move The move to execute
-	 * @return The captures piece, or null if the move's destination was empty
 	 */
 	public void move(Move move) {
 		Piece	piece			= getPos(move);
@@ -107,6 +140,11 @@ public class Board implements Cloneable {
 				// TODO: Select promotion
 				setDest(move, new Queen(piece.getColor(), this));
 				break;
+			case EN_PASSANT:
+				setDest(move, piece);
+				setPos(move, null);
+				boardArr[move.dest.x][move.dest.y - move.ySign] = null;
+				break;
 			case CASTLING:
 				// Move the king
 				setDest(move, piece);
@@ -135,26 +173,34 @@ public class Board implements Cloneable {
 		// Increment move counter
 		getDest(move).incMoveCounter();
 
-		// Update the king's position if the moved piece is the king
+		// Update the king's position if the moved piece is the king and castling
+		// availability
 		if (piece.getType() == Type.KING) kingPos.put(piece.getColor(), move.dest);
 
 		// Update log
-		log.add(move, capturePiece);
+		log.add(move, capturePiece, piece.getType() == Type.PAWN);
+
+		updateCastlingRights();
 	}
 
 	/**
 	 * Reverts the last move.
 	 */
 	public void revert() {
-		LoggedMove	loggedMove		= log.getLast();
+		MoveNode	moveNode		= log.getLast();
-		Move		move			= loggedMove.move;
+		Move		move			= moveNode.move;
-		Piece		capturedPiece	= loggedMove.capturedPiece;
+		Piece		capturedPiece	= moveNode.capturedPiece;
 
 		switch (move.type) {
 			case PAWN_PROMOTION:
 				setPos(move, new Pawn(getDest(move).getColor(), this));
 				setDest(move, capturedPiece);
 				break;
+			case EN_PASSANT:
+				setPos(move, getDest(move));
+				setDest(move, null);
+				boardArr[move.dest.x][move.dest.y - move.ySign] = new Pawn(getPos(move).getColor().opposite(), this);
+				break;
 			case CASTLING:
 				// Move the king
 				setPos(move, getDest(move));
@@ -163,8 +209,6 @@ public class Board implements Cloneable {
 				// 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);
 
@@ -188,6 +232,30 @@ public class Board implements Cloneable {
 
 		// Update log
 		log.removeLast();
+
+		updateCastlingRights();
+	}
+
+	private void updateCastlingRights() {
+		// White
+		if (new Position(4, 7).equals(kingPos.get(Color.WHITE))) {
+			final King king = (King) get(kingPos.get(Color.WHITE));
+			castlingRights.get(Color.WHITE).put(Type.KING, king.canCastleKingside());
+			castlingRights.get(Color.WHITE).put(Type.QUEEN, king.canCastleQueenside());
+		} else {
+			castlingRights.get(Color.WHITE).put(Type.KING, false);
+			castlingRights.get(Color.WHITE).put(Type.QUEEN, false);
+		}
+
+		// Black
+		if (new Position(4, 0).equals(kingPos.get(Color.BLACK))) {
+			final King king = (King) get(kingPos.get(Color.BLACK));
+			castlingRights.get(Color.BLACK).put(Type.KING, king.canCastleKingside());
+			castlingRights.get(Color.BLACK).put(Type.QUEEN, king.canCastleQueenside());
+		} else {
+			castlingRights.get(Color.BLACK).put(Type.KING, false);
+			castlingRights.get(Color.BLACK).put(Type.QUEEN, false);
+		}
 	}
 
 	/**
@@ -249,7 +317,8 @@ public class Board implements Cloneable {
 
 	public GameState getGameEventType(Color color) {
 		return checkCheck(color) ? checkCheckmate(color) ? GameState.CHECKMATE : GameState.CHECK
-				: getMoves(color).isEmpty() ? GameState.STALEMATE : GameState.NORMAL;
+				: getMoves(color).isEmpty() || log.getLast().halfmoveClock >= 50 ? GameState.STALEMATE
+						: GameState.NORMAL;
 	}
 
 	/**
@@ -289,7 +358,7 @@ public class Board implements Cloneable {
 	/**
 	 * Initialized the board array with the default chess pieces and positions.
 	 */
-	public void initializeDefaultPositions() {
+	public void initDefaultPositions() {
 		// Initialize pawns
 		for (int i = 0; i < 8; i++) {
 			boardArr[i][1]	= new Pawn(Color.BLACK, this);
@@ -330,56 +399,204 @@ public class Board implements Cloneable {
 		for (int i = 0; i < 8; i++)
 			for (int j = 2; j < 6; j++)
 				boardArr[i][j] = null;
+
+		// Initialize castling rights
+		Map<Type, Boolean> whiteCastling = new HashMap<>(), blackCastling = new HashMap<>();
+		whiteCastling.put(Type.KING, true);
+		whiteCastling.put(Type.QUEEN, true);
+		blackCastling.put(Type.KING, true);
+		blackCastling.put(Type.QUEEN, true);
+		castlingRights.put(Color.WHITE, whiteCastling);
+		castlingRights.put(Color.BLACK, blackCastling);
+
+		log.reset();
 	}
 
 	/**
-	 * @return A new instance of this class with a shallow copy of both
+	 * Initialized the board with a position specified in a FEN-encoded string.
-	 *         {@code kingPos} and {code boardArr}
+	 * 
+	 * @param fen The FEN-encoded string representing target state of the board
 	 */
-	@Override
+	public void initFromFEN(String fen) {
-	public Object clone() {
+		String[] parts = fen.split(" ");
-		Board board = null;
+		log.reset();
-		try {
+
-			board = (Board) super.clone();
+		// Piece placement (from white's perspective)
-		} catch (CloneNotSupportedException ex) {
+		String[] rows = parts[0].split("/");
-			ex.printStackTrace();
+		for (int i = 0; i < 8; i++) {
-		}
+			char[] places = rows[i].toCharArray();
-		board.boardArr = new Piece[8][8];
+			for (int j = 0, k = 0; k < places.length; j++, k++) {
-		for (int i = 0; i < 8; i++)
+				if (Character.isDigit(places[k])) {
-			for (int j = 0; j < 8; j++) {
+					for (int l = j; l < Character.digit(places[k], 10); l++, j++)
-				if (boardArr[i][j] == null) continue;
+						boardArr[j][i] = null;
-				board.boardArr[i][j]		= (Piece) boardArr[i][j].clone();
+					--j;
-				board.boardArr[i][j].board	= board;
+				} else {
+					Color color = Character.isUpperCase(places[k]) ? Color.WHITE : Color.BLACK;
+					switch (Character.toLowerCase(places[k])) {
+						case 'k':
+							boardArr[j][i] = new King(color, this);
+							kingPos.put(color, new Position(j, i));
+							break;
+						case 'q':
+							boardArr[j][i] = new Queen(color, this);
+							break;
+						case 'r':
+							boardArr[j][i] = new Rook(color, this);
+							break;
+						case 'n':
+							boardArr[j][i] = new Knight(color, this);
+							break;
+						case 'b':
+							boardArr[j][i] = new Bishop(color, this);
+							break;
+						case 'p':
+							boardArr[j][i] = new Pawn(color, this);
+							break;
+						default:
+							System.err.printf("Unknown character '%c' in board declaration of FEN string '%s'%n",
+									places[k],
+									fen);
+					}
+				}
 			}
+		}
 
-		board.kingPos = new HashMap<>();
+		// Active color
-		board.kingPos.putAll(kingPos);
+		log.setActiveColor(Color.fromFirstChar(parts[1].charAt(0)));
 
-		board.log = (Log) log.clone();
+		// Castling rights
+		Map<Type, Boolean> whiteCastling = new HashMap<>(), blackCastling = new HashMap<>();
+		for (char c : parts[2].toCharArray())
+			switch (c) {
+				case 'K':
+					whiteCastling.put(Type.KING, true);
+				case 'Q':
+					whiteCastling.put(Type.QUEEN, true);
+				case 'k':
+					blackCastling.put(Type.KING, true);
+				case 'q':
+					blackCastling.put(Type.QUEEN, true);
+				case '-':
+					break;
+				default:
+					System.err
+						.printf("Unknown character '%c' in castling rights declaration of FEN string '%s'", c, fen);
+			}
+		castlingRights.put(Color.WHITE, whiteCastling);
+		castlingRights.put(Color.BLACK, blackCastling);
 
-		return board;
+		// En passant availability
+		if (!parts[3].equals("-")) log.setEnPassant(Position.fromSAN(parts[3]));
+
+		// Halfmove clock
+		log.setHalfmoveClock(Integer.parseInt(parts[4]));
+
+		// Fullmove counter
+		log.setFullmoveCounter(Integer.parseInt(parts[5]));
 	}
 
+	/**
+	 * @return a FEN-encoded string representing the board
+	 */
+	public String toFEN() {
+		StringBuilder sb = new StringBuilder();
+
+		// Piece placement (from white's perspective)
+		for (int i = 0; i < 8; i++) {
+			int emptyCount = 0;
+			for (int j = 0; j < 8; j++) {
+				final Piece piece = boardArr[j][i];
+				if (piece == null) ++emptyCount;
+				else {
+					if (emptyCount != 0) {
+						sb.append(emptyCount);
+						emptyCount = 0;
+					}
+					char p = boardArr[j][i].getType().firstChar();
+					sb.append(piece.getColor() == Color.WHITE ? Character.toUpperCase(p) : p);
+				}
+			}
+			if (emptyCount != 0) sb.append(emptyCount);
+			if (i < 7) sb.append('/');
+		}
+
+		// Active color
+		sb.append(" " + log.getActiveColor().firstChar());
+
+		// Castling Rights
+		sb.append(' ');
+		StringBuilder castlingSb = new StringBuilder();
+		if (castlingRights.get(Color.WHITE).get(Type.KING)) castlingSb.append('K');
+		if (castlingRights.get(Color.WHITE).get(Type.QUEEN)) castlingSb.append('Q');
+		if (castlingRights.get(Color.BLACK).get(Type.KING)) castlingSb.append('k');
+		if (castlingRights.get(Color.BLACK).get(Type.QUEEN)) castlingSb.append('q');
+		if (castlingSb.length() == 0) sb.append("-");
+		sb.append(castlingSb);
+
+		final MoveNode lastMove = log.getLast();
+
+		// En passant availability
+		sb.append(" " + (lastMove == null || lastMove.enPassant == null ? "-" : lastMove.enPassant.toSAN()));
+
+		// Halfmove clock
+		sb.append(" " + String.valueOf(lastMove == null ? 0 : lastMove.halfmoveClock));
+
+		// Fullmove counter
+		sb.append(" " + String.valueOf(lastMove == null ? 1 : lastMove.fullmoveCounter));
+
+		return sb.toString();
+	}
+
+	/**
+	 * @param pos The position from which to return a piece
+	 * @return The piece at the position
+	 */
 	public Piece get(Position pos) {
 		return boardArr[pos.x][pos.y];
 	}
 
+	/**
+	 * Places a piece at a position.
+	 * 
+	 * @param pos   The position to place the piece at
+	 * @param piece The piece to place
+	 */
 	public void set(Position pos, Piece piece) {
 		boardArr[pos.x][pos.y] = piece;
 	}
 
+	/**
+	 * @param move The move from which position to return a piece
+	 * @return The piece at the position of the move
+	 */
 	public Piece getPos(Move move) {
 		return get(move.pos);
 	}
 
+	/**
+	 * @param move The move from which destination to return a piece
+	 * @return The piece at the destination of the move
+	 */
 	public Piece getDest(Move move) {
 		return get(move.dest);
 	}
 
+	/**
+	 * Places a piece at the position of a move.
+	 * 
+	 * @param move  The move at which position to place the piece
+	 * @param piece The piece to place
+	 */
 	public void setPos(Move move, Piece piece) {
 		set(move.pos, piece);
 	}
 
+	/**
+	 * Places a piece at the destination of a move.
+	 * 
+	 * @param move  The move at which destination to place the piece
+	 * @param piece The piece to place
+	 */
 	public void setDest(Move move, Piece piece) {
 		set(move.dest, piece);
 	}
@@ -388,4 +605,9 @@ public class Board implements Cloneable {
 	 * @return The board array
 	 */
 	public Piece[][] getBoardArr() { return boardArr; }
+
+	/**
+	 * @return The move log
+	 */
+	public Log getLog() { return log; }
 }

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

@@ -18,27 +18,40 @@ public class King extends Piece {
 	@Override
 	public boolean isValidMove(Move move) {
 		// Castling
-		if (getMoveCounter() == 0 && move.xDist == 2 && move.yDist == 0) {
+		if (move.xDist == 2 && move.yDist == 0) {
-
+			if (canCastleKingside()) {
-			// 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;
 			}
-
+			if (canCastleQueenside()) {
-			// 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);
 	}
 
+	public boolean canCastleKingside() {
+		if (getMoveCounter() == 0) {
+			int			y		= getColor() == Color.WHITE ? 7 : 0;
+			Position	rookPos	= new Position(7, y);
+			Piece		rook	= board.get(rookPos);
+			return rook != null && rook.getType() == Type.ROOK && rook.getMoveCounter() == 0
+					&& isFreePath(new Move(new Position(4, y), new Position(6, y)));
+		} else return false;
+	}
+
+	public boolean canCastleQueenside() {
+		if (getMoveCounter() == 0) {
+			int			y		= getColor() == Color.WHITE ? 7 : 0;
+			Position	rookPos	= new Position(0, y);
+			Piece		rook	= board.get(rookPos);
+			return rook != null && rook.getType() == Type.ROOK && rook.getMoveCounter() == 0
+					&& isFreePath(new Move(new Position(4, y), new Position(1, y)));
+		} else return false;
+	}
+
 	@Override
 	protected List<Move> getPseudolegalMoves(Position pos) {
 		List<Move> moves = new ArrayList<>();
@@ -50,31 +63,13 @@ public class King extends Piece {
 				}
 
 		// Castling
-		// TODO: Check attacked squares in between
+		// TODO: Condition: cannot castle out of, through or into check
-		// TODO: Castling out of check?
+		if (canCastleKingside()) moves.add(new Move(pos, new Position(6, pos.y), Move.Type.CASTLING));
-		if (getMoveCounter() == 0) {
+		if (canCastleQueenside()) moves.add(new Move(pos, new Position(2, pos.y), Move.Type.CASTLING));
-
-			// 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/Log.java

@@ -3,53 +3,198 @@ package dev.kske.chess.board;
 import java.util.ArrayList;
 import java.util.List;
 
+import dev.kske.chess.board.Piece.Color;
+
 /**
  * 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 {
+public class Log {
 
-	private List<LoggedMove> moves;
+	private MoveNode root, current;
+
+	private Position	enPassant;
+	private Color		activeColor;
+	private int			fullmoveCounter, halfmoveClock;
 
 	public Log() {
-		moves = new ArrayList<>();
+		reset();
 	}
 
-	public void add(Move move, Piece capturedPiece) {
+	/**
-		moves.add(new LoggedMove(move, capturedPiece));
+	 * Creates a (partially deep) copy of another {@link Log} instance which begins
-	}
+	 * with the current {@link MoveNode}.
+	 * 
+	 * @param other          The {@link Log} instance to copy
+	 * @param copyVariations If set to {@code true}, subsequent variations of the
+	 *                       current {@link MoveNode} are copied with the
+	 *                       {@link Log}
+	 */
+	public Log(Log other, boolean copyVariations) {
+		enPassant		= other.enPassant;
+		activeColor		= other.activeColor;
+		fullmoveCounter	= other.fullmoveCounter;
+		halfmoveClock	= other.halfmoveClock;
 
-	public LoggedMove getLast() {
+		// The new root is the current node of the copied instance
-		return moves.get(moves.size() - 1);
+		if (!other.isEmpty()) {
-	}
+			root		= new MoveNode(other.current, copyVariations);
-	
+			root.parent	= null;
-	public void removeLast() {
+			current		= root;
-		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 {
+	/**
+	 * Adds a move to the move history and adjusts the log to the new position.
+	 * 
+	 * @param move          The move to log
+	 * @param capturedPiece The piece captured with the move
+	 * @param pawnMove      {@code true} if the move was made by a pawn
+	 */
+	public void add(Move move, Piece capturedPiece, boolean pawnMove) {
+		enPassant = pawnMove && move.yDist == 2 ? new Position(move.pos.x, move.pos.y + move.ySign) : null;
+		if (activeColor == Color.BLACK) ++fullmoveCounter;
+		if (pawnMove || capturedPiece != null) halfmoveClock = 0;
+		else++halfmoveClock;
+		activeColor = activeColor.opposite();
+		final MoveNode leaf = new MoveNode(move, capturedPiece, enPassant, activeColor, fullmoveCounter, halfmoveClock);
+
+		if (isEmpty()) {
+			root	= leaf;
+			current	= leaf;
+		} else {
+			current.addVariation(leaf);
+			current = leaf;
+		}
+	}
+
+	/**
+	 * Removed the last move from the log and adjusts its state to the previous
+	 * move.
+	 */
+	public void removeLast() {
+		if (!isEmpty() && current.parent != null) {
+			current.parent.variations.remove(current);
+			current			= current.parent;
+			activeColor		= current.activeColor;
+			enPassant		= current.enPassant;
+			fullmoveCounter	= current.fullmoveCounter;
+			halfmoveClock	= current.halfmoveClock;
+		} else reset();
+	}
+
+	public boolean isEmpty() { return root == null; }
+
+	/**
+	 * Reverts the log to its initial state corresponding to the default board
+	 * position.
+	 */
+	public void reset() {
+		root			= null;
+		current			= null;
+		enPassant		= null;
+		activeColor		= Color.WHITE;
+		fullmoveCounter	= 1;
+		halfmoveClock	= 0;
+	}
+
+	/**
+	 * @return The first logged move, or {@code null} if there is none
+	 */
+	public MoveNode getRoot() { return root; }
+
+	/**
+	 * @return the last logged move, or {@code null} if there is none
+	 */
+	public MoveNode getLast() { return current; }
+
+	public Position getEnPassant() { return enPassant; }
+
+	public void setEnPassant(Position enPassant) { this.enPassant = enPassant; }
+
+	public Color getActiveColor() { return activeColor; }
+
+	public void setActiveColor(Color activeColor) { this.activeColor = activeColor; }
+
+	public int getFullmoveCounter() { return fullmoveCounter; }
+
+	public void setFullmoveCounter(int fullmoveCounter) { this.fullmoveCounter = fullmoveCounter; }
+
+	public int getHalfmoveClock() { return halfmoveClock; }
+
+	public void setHalfmoveClock(int halfmoveClock) { this.halfmoveClock = halfmoveClock; }
+
+	public static class MoveNode {
 
 		public final Move		move;
-		public final Piece	capturedPiece;
+		public final Piece		capturedPiece;
+		public final Position	enPassant;
+		public final Color		activeColor;
+		public final int		fullmoveCounter, halfmoveClock;
 
-		public LoggedMove(Move move, Piece capturedPiece) {
+		private MoveNode		parent;
-			this.move		= move;
+		private List<MoveNode>	variations;
-			this.capturedPiece	= capturedPiece;
+
+		/**
+		 * Creates a new {@link MoveNode}.
+		 * 
+		 * @param move            The logged {@link Move}
+		 * @param capturedPiece   The {@link Piece} captures by the logged {@link Move}
+		 * @param enPassant       The en passant {@link Position} valid after the logged
+		 *                        {@link Move}, or {@code null} if there is none
+		 * @param activeColor     The {@link Color} active after the logged {@link Move}
+		 * @param fullmoveCounter
+		 * @param halfmoveClock
+		 */
+		public MoveNode(Move move, Piece capturedPiece, Position enPassant, Color activeColor, int fullmoveCounter,
+				int halfmoveClock) {
+			this.move				= move;
+			this.capturedPiece		= capturedPiece;
+			this.enPassant			= enPassant;
+			this.activeColor		= activeColor;
+			this.fullmoveCounter	= fullmoveCounter;
+			this.halfmoveClock		= halfmoveClock;
 		}
+
+		/**
+		 * Creates a (deep) copy of another {@link MoveNode}.
+		 * 
+		 * @param other          The {@link MoveNode} to copy
+		 * @param copyVariations When this is set to {@code true} a deep copy is
+		 *                       created, which
+		 *                       considers subsequent variations
+		 */
+		public MoveNode(MoveNode other, boolean copyVariations) {
+			this(other.move, other.capturedPiece, other.enPassant, other.activeColor, other.fullmoveCounter,
+					other.halfmoveClock);
+			if (copyVariations && other.variations != null) {
+				if (variations == null) variations = new ArrayList<>();
+				other.variations.forEach(variation -> {
+					MoveNode copy = new MoveNode(variation, true);
+					copy.parent = this;
+					variations.add(copy);
+				});
+			}
+		}
+
+		/**
+		 * Adds another {@link MoveNode} as a child node.
+		 * 
+		 * @param variation The {@link MoveNode} to append to this {@link MoveNode}
+		 */
+		public void addVariation(MoveNode variation) {
+			if (variations == null) variations = new ArrayList<>();
+			if (!variations.contains(variation)) {
+				variations.add(variation);
+				variation.parent = this;
+			}
+		}
+
+		/**
+		 * @return A list of all variations associated with this {@link MoveNode}
+		 */
+		public List<MoveNode> getVariations() { return variations; }
 	}
-}
+}

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

@@ -30,6 +30,15 @@ public class Move {
 		this(new Position(xPos, yPos), new Position(xDest, yDest));
 	}
 
+	public static Move fromSAN(String move) {
+		return new Move(Position.fromSAN(move.substring(0, 2)),
+				Position.fromSAN(move.substring(2)));
+	}
+
+	public String toSAN() {
+		return pos.toSAN() + dest.toSAN();
+	}
+
 	public boolean isHorizontal() { return yDist == 0; }
 
 	public boolean isVertical() { return xDist == 0; }

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

@@ -17,10 +17,10 @@ public class Pawn extends Piece {
 
 	@Override
 	public boolean isValidMove(Move move) {
-		// TODO: en passant
 		boolean	step		= move.isVertical() && move.yDist == 1;
 		boolean	doubleStep	= move.isVertical() && move.yDist == 2;
 		boolean	strafe		= move.isDiagonal() && move.xDist == 1;
+		boolean	enPassant	= false;
 		if (getColor() == Color.WHITE) doubleStep &= move.pos.y == 6;
 		else doubleStep &= move.pos.y == 1;
 
@@ -28,7 +28,14 @@ public class Pawn extends Piece {
 		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);
+		// Mark the move as en passant if necessary
+		if (strafe && move.dest.equals(board.getLog().getEnPassant())) {
+			enPassant	= true;
+			move.type	= Move.Type.EN_PASSANT;
+		}
+
+		return enPassant || (step ^ doubleStep ^ strafe) && move.ySign == (getColor() == Color.WHITE ? -1 : 1)
+				&& isFreePath(move);
 	}
 
 	@Override
@@ -72,10 +79,16 @@ public class Pawn extends Piece {
 			if (isFreePath(move)) moves.add(move);
 		}
 
-		// Mark moves as pawn promotions if necessary
+		// Mark moves as pawn promotion if necessary
 		if (sign == 1 && pos.y == 6 || sign == -1 && pos.y == 1)
 			moves.parallelStream().forEach(m -> m.type = Move.Type.PAWN_PROMOTION);
 
+		// Add en passant move if necessary
+		if (board.getLog().getEnPassant() != null) {
+			Move move = new Move(pos, board.getLog().getEnPassant(), Move.Type.EN_PASSANT);
+			if (move.isDiagonal() && move.xDist == 1) moves.add(move);
+		}
+
 		return moves;
 	}
 

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

@@ -35,8 +35,16 @@ public abstract class Piece implements Cloneable {
 
 	public abstract boolean isValidMove(Move move);
 
+	/**
+	 * Checks, if the squares between the position and the destination of a move are
+	 * free.
+	 * 
+	 * @param move The move to check
+	 */
 	protected boolean isFreePath(Move move) {
-		// Only check destination by default
+		for (int i = move.pos.x + move.xSign, j = move.pos.y + move.ySign; i != move.dest.x
+				|| j != move.dest.y; i += move.xSign, j += move.ySign)
+			if (board.getBoardArr()[i][j] != null) return false;
 		return checkDestination(move);
 	}
 
@@ -77,12 +85,27 @@ public abstract class Piece implements Cloneable {
 	}
 
 	public static enum Type {
-		KING, QUEEN, ROOK, KNIGHT, BISHOP, PAWN
+		KING, QUEEN, ROOK, KNIGHT, BISHOP, PAWN;
+		
+		/**
+		 * @return The first character of this {@link Type} in algebraic notation and lower case
+		 */
+		public char firstChar() {
+			return this == KNIGHT ? 'n' : Character.toLowerCase(this.toString().charAt(0));
+		}
 	}
 
 	public static enum Color {
 		WHITE, BLACK;
 
+		public static Color fromFirstChar(char c) {
+			return Character.toLowerCase(c) == 'w' ? WHITE : BLACK;
+		}
+
+		public char firstChar() {
+			return this == WHITE ? 'w' : 'b';
+		}
+
 		public Color opposite() {
 			return this == WHITE ? BLACK : WHITE;
 		}

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

@@ -15,8 +15,36 @@ public class Position {
 		this.y	= y;
 	}
 
+	public static Position fromSAN(String pos) {
+		return new Position(pos.charAt(0) - 97, 8 - Character.getNumericValue(pos.charAt(1)));
+	}
+
+	public String toSAN() {
+		return String.valueOf((char) (x + 97)) + String.valueOf(8 - y);
+	}
+
 	@Override
 	public String toString() {
 		return String.format("[%d, %d]", x, y);
 	}
+
+	@Override
+	public int hashCode() {
+		final int	prime	= 31;
+		int			result	= 1;
+		result	= prime * result + x;
+		result	= prime * result + y;
+		return result;
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj) return true;
+		if (obj == null) return false;
+		if (getClass() != obj.getClass()) return false;
+		Position other = (Position) obj;
+		if (x != other.x) return false;
+		if (y != other.y) return false;
+		return true;
+	}
 }

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

@@ -20,22 +20,6 @@ public class Queen extends Piece {
 		return ((move.isHorizontal() || move.isVertical()) || move.isDiagonal()) && isFreePath(move);
 	}
 
-	@Override
-	protected boolean isFreePath(Move move) {
-		if (move.isHorizontal()) {
-			for (int i = move.pos.x + move.xSign; i != move.dest.x; i += move.xSign)
-				if (board.getBoardArr()[i][move.pos.y] != null) return false;
-		} else if (move.isVertical()) {
-			for (int i = move.pos.y + move.ySign; i != move.dest.y; i += move.ySign)
-				if (board.getBoardArr()[move.pos.x][i] != null) return false;
-		} else {
-			for (int i = move.pos.x + move.xSign, j = move.pos.y
-					+ move.ySign; i != move.dest.x; i += move.xSign, j += move.ySign)
-				if (board.getBoardArr()[i][j] != null) return false;
-		}
-		return checkDestination(move);
-	}
-
 	@Override
 	protected List<Move> getPseudolegalMoves(Position pos) {
 		List<Move> moves = new ArrayList<>();

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

@@ -20,18 +20,6 @@ public class Rook extends Piece {
 		return (move.isHorizontal() || move.isVertical()) && isFreePath(move);
 	}
 
-	@Override
-	protected boolean isFreePath(Move move) {
-		if (move.isHorizontal()) {
-			for (int i = move.pos.x + move.xSign; i != move.dest.x; i += move.xSign)
-				if (board.getBoardArr()[i][move.pos.y] != null) return false;
-		} else {
-			for (int i = move.pos.y + move.ySign; i != move.dest.y; i += move.ySign)
-				if (board.getBoardArr()[move.pos.x][i] != null) return false;
-		}
-		return checkDestination(move);
-	}
-
 	@Override
 	protected List<Move> getPseudolegalMoves(Position pos) {
 		List<Move> moves = new ArrayList<>();

src/dev/kske/chess/event/Event.java

@@ -0,0 +1,15 @@
+package dev.kske.chess.event;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>Event.java</strong><br>
+ * Created: <strong>7 Aug 2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public interface Event<T> {
+
+	/**
+	 * @return The data associated with the event
+	 */
+	T getData();
+}

src/dev/kske/chess/event/EventBus.java

@@ -0,0 +1,36 @@
+package dev.kske.chess.event;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>EventBus.java</strong><br>
+ * Created: <strong>7 Aug 2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class EventBus {
+
+	private List<Subscribable> subscribers;
+
+	private static EventBus instance;
+
+	public static EventBus getInstance() {
+		if (instance == null) instance = new EventBus();
+		return instance;
+	}
+
+	private EventBus() {
+		subscribers = new ArrayList<>();
+	}
+
+	public void register(Subscribable subscribable) {
+		subscribers.add(subscribable);
+	}
+
+	public void dispatch(Event<?> event) {
+		subscribers.stream().filter(e -> e.supports().contains(event.getClass())).forEach(e -> e.handle(event));
+	}
+
+	public List<Subscribable> getSubscribers() { return subscribers; }
+}

src/dev/kske/chess/event/MoveEvent.java

@@ -0,0 +1,21 @@
+package dev.kske.chess.event;
+
+import dev.kske.chess.board.Move;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>MoveEvent.java</strong><br>
+ * Created: <strong>7 Aug 2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class MoveEvent implements Event<Move> {
+
+	private final Move move;
+
+	public MoveEvent(Move move) {
+		this.move = move;
+	}
+
+	@Override
+	public Move getData() { return move; }
+}

src/dev/kske/chess/event/Subscribable.java

@@ -0,0 +1,24 @@
+package dev.kske.chess.event;
+
+import java.util.Set;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>Subscribable.java</strong><br>
+ * Created: <strong>7 Aug 2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public interface Subscribable {
+
+	/**
+	 * Consumes an event dispatched by an event bus.
+	 * 
+	 * @param event The event dispatched by the event bus, only of supported type
+	 */
+	void handle(Event<?> event);
+
+	/**
+	 * @return A set of classes this class is supposed to handle in events
+	 */
+	Set<Class<?>> supports();
+}

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

@@ -3,13 +3,19 @@ package dev.kske.chess.game;
 import java.util.HashMap;
 import java.util.Map;
 
+import javax.swing.JOptionPane;
+
 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.event.EventBus;
+import dev.kske.chess.event.MoveEvent;
 import dev.kske.chess.game.ai.AIPlayer;
 import dev.kske.chess.ui.BoardComponent;
 import dev.kske.chess.ui.BoardPane;
+import dev.kske.chess.ui.EngineUtil;
+import dev.kske.chess.ui.EngineUtil.EngineInfo;
 import dev.kske.chess.ui.OverlayComponent;
 
 /**
@@ -20,85 +26,119 @@ import dev.kske.chess.ui.OverlayComponent;
  */
 public class Game {
 
-	private Map<Color, Player>	players;
+	private Map<Color, Player>	players	= new HashMap<>();
 	private Board				board;
 	private OverlayComponent	overlayComponent;
 	private BoardComponent		boardComponent;
 
-	public Game(Map<Color, Player> players, BoardPane boardPane) {
+	public Game(BoardPane boardPane, String whiteName, String blackName) {
-		this.players			= players;
+		board				= new Board();
-		this.overlayComponent	= boardPane.getOverlayComponent();
+		init(boardPane, whiteName, blackName);
-		this.boardComponent		= boardPane.getBoardComponent();
+	}
-		this.board				= new Board();
+
+	public Game(BoardPane boardPane, String whiteName, String blackName, String fen) {
+		board = new Board(fen);
+		init(boardPane, whiteName, blackName);
+	}
+
+	private void init(BoardPane boardPane, String whiteName, String blackName) {
+
+		// Initialize / synchronize UI
+		overlayComponent	= boardPane.getOverlayComponent();
+		boardComponent		= boardPane.getBoardComponent();
 		boardComponent.setBoard(board);
 
+		// Initialize players
+		players.put(Color.WHITE, getPlayer(whiteName, Color.WHITE));
+		players.put(Color.BLACK, getPlayer(blackName, Color.BLACK));
+
 		// Initialize the game variable in each player
 		players.values().forEach(player -> player.setGame(this));
 	}
 
-	public static Game createNatural(BoardPane boardPane) {
+	private Player getPlayer(String name, Color color) {
-		Map<Color, Player>	players	= new HashMap<>();
+		switch (name) {
-		OverlayComponent	overlay	= boardPane.getOverlayComponent();
+			case "Natural Player":
-
+				return new NaturalPlayer(color, overlayComponent);
-		players.put(Color.WHITE, new NaturalPlayer(Color.WHITE, overlay));
+			case "AI Player":
-		players.put(Color.BLACK, new NaturalPlayer(Color.BLACK, overlay));
+				return new AIPlayer(color, 4, -10);
-		return new Game(players, boardPane);
+			default:
-	}
+				for (EngineInfo info : EngineUtil.getEngineInfos())
-
+					if (info.name.equals(name)) return new UCIPlayer(color, info.path);
-	public static Game createNaturalVsAI(BoardPane boardPane, int maxDepth, int alphaBeta) {
+				System.err.println("Invalid player name: " + name);
-		Map<Color, Player>	players	= new HashMap<>();
+				return null;
-		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) {
 		if (board.getPos(move).getColor() == player.color && board.attemptMove(move)) {
+
+			// Redraw
+			boardComponent.repaint();
+			overlayComponent.displayArrow(move);
+
+			// Run garbage collection
+			System.gc();
+
 			System.out.printf("%s: %s%n", player.color, move);
+			System.out.println("FEN: " + board.toFEN());
+			EventBus.getInstance().dispatch(new MoveEvent(move));
 			GameState eventType = board.getGameEventType(board.getDest(move).getColor().opposite());
 			switch (eventType) {
 				case CHECKMATE:
 				case STALEMATE:
-					System.out.printf("%s in %s!%n", player.color.opposite(), eventType);
+					String result = String.format("%s in %s!%n", player.color.opposite(), eventType);
+					System.out.print(result);
+					JOptionPane.showMessageDialog(boardComponent, result);
 					break;
 				case CHECK:
 					System.out.printf("%s in check!%n", player.color.opposite());
 				default:
-					boardComponent.repaint();
+					players.get(board.getLog().getActiveColor()).requestMove();
-					players.get(player.color.opposite()).requestMove();
 			}
-			overlayComponent.displayArrow(move);
 		} else player.requestMove();
 	}
 
 	public void start() {
-		players.get(Color.WHITE).requestMove();
+		players.get(board.getLog().getActiveColor()).requestMove();
 	}
 
 	public void reset() {
-		players.forEach((k, v) -> v.cancelMove());
+		players.values().forEach(Player::cancelMove);
-		board.initializeDefaultPositions();
+		board.initDefaultPositions();
 		boardComponent.repaint();
 		overlayComponent.clearDots();
 		overlayComponent.clearArrow();
 	}
 
 	/**
-	 * Removed all connections between the game and the ui.
+	 * Stops the game by disconnecting its players form the UI.
 	 */
-	public void disconnect() {
+	public void stop() {
 		players.values().forEach(Player::disconnect);
 	}
 
+	/**
+	 * Assigns the players their opposite colors.
+	 */
+	public void swapColors() {
+		players.values().forEach(Player::cancelMove);
+		Player	white	= players.get(Color.WHITE);
+		Player	black	= players.get(Color.BLACK);
+		white.setColor(Color.BLACK);
+		black.setColor(Color.WHITE);
+		players.put(Color.WHITE, black);
+		players.put(Color.BLACK, white);
+		players.get(board.getLog().getActiveColor()).requestMove();
+	}
+
+	/**
+	 * @return The board on which this game's moves are made
+	 */
 	public Board getBoard() { return board; }
+
+	/**
+	 * @return The players participating in this game
+	 */
+	public Map<Color, Player> getPlayers() { return players; }
 }

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

@@ -28,6 +28,7 @@ public class NaturalPlayer extends Player implements MouseListener {
 	public NaturalPlayer(Color color, OverlayComponent overlayComponent) {
 		super(color);
 		this.overlayComponent	= overlayComponent;
+		name					= "Player";
 		moveRequested			= false;
 
 		overlayComponent.addMouseListener(this);
@@ -55,7 +56,7 @@ public class NaturalPlayer extends Player implements MouseListener {
 			pos = new Position(evt.getPoint().x / overlayComponent.getTileSize(),
 					evt.getPoint().y / overlayComponent.getTileSize());
 
-			Board board = (Board) NaturalPlayer.this.board.clone();
+			Board board = new Board(this.board);
 			if (board.get(pos) != null && board.get(pos).getColor() == color) {
 				List<Position> positions = board.getMoves(pos)
 					.stream()

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

@@ -11,9 +11,10 @@ import dev.kske.chess.board.Piece.Color;
  */
 public abstract class Player {
 
-	protected Game	game;
+	protected Game		game;
-	protected Board	board;
+	protected Board		board;
-	protected Color	color;
+	protected Color		color;
+	protected String	name;
 
 	public Player(Color color) {
 		this.color = color;
@@ -39,4 +40,8 @@ public abstract class Player {
 	public Color getColor() { return color; }
 
 	public void setColor(Color color) { this.color = color; }
+
+	public String getName() { return name; }
+
+	public void setName(String name) { this.name = name; }
 }

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

@@ -0,0 +1,92 @@
+package dev.kske.chess.game;
+
+import java.io.IOException;
+
+import dev.kske.chess.board.Move;
+import dev.kske.chess.board.Piece.Color;
+import dev.kske.chess.uci.UCIHandle;
+import dev.kske.chess.uci.UCIListener;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>UCIPlayer.java</strong><br>
+ * Created: <strong>18.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class UCIPlayer extends Player implements UCIListener {
+
+	private UCIHandle		handle;
+
+	public UCIPlayer(Color color, String enginePath) {
+		super(color);
+		try {
+			handle = new UCIHandle(enginePath);
+			handle.setListener(this);
+			handle.start();
+		} catch (IOException ex) {
+			ex.printStackTrace();
+		}
+	}
+
+	@Override
+	public void requestMove() {
+		handle.positionFEN(board.toFEN());
+		handle.go();
+	}
+
+	@Override
+	public void cancelMove() {
+		handle.stop();
+	}
+
+	@Override
+	public void disconnect() {
+		handle.quit();
+	}
+
+	@Override
+	public void onIdName(String name) {
+		this.name = name;
+	}
+
+	@Override
+	public void onBestMove(String move) {
+		Move moveObj = Move.fromSAN(move);
+		game.onMove(this, moveObj);
+	}
+
+	@Override
+	public void onBestMove(String move, Move ponderMove) {
+		onBestMove(move);
+	}
+
+	@Override
+	public void onCopyProtectionChecking() {
+		System.out.println("Copy protection checking...");
+	}
+
+	@Override
+	public void onCopyProtectionOk() {
+		System.out.println("Copy protection ok");
+	}
+
+	@Override
+	public void onCopyProtectionError() {
+		System.err.println("Copy protection error!");
+	}
+
+	@Override
+	public void onRegistrationChecking() {
+		System.out.println("Registration checking...");
+	}
+
+	@Override
+	public void onRegistrationOk() {
+		System.out.println("Registration ok");
+	}
+
+	@Override
+	public void onRegistrationError() {
+		System.err.println("Registration error!");
+	}
+}

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

@@ -32,6 +32,7 @@ public class AIPlayer extends Player {
 
 	public AIPlayer(Color color, int maxDepth, int alphaBetaThreshold) {
 		super(color);
+		name					= "AIPlayer";
 		availableProcessors		= Runtime.getRuntime().availableProcessors();
 		this.maxDepth			= maxDepth;
 		this.alphaBetaThreshold	= alphaBetaThreshold;
@@ -49,7 +50,7 @@ public class AIPlayer extends Player {
 			/*
 			 * Get a copy of the board and the available moves.
 			 */
-			Board		board	= (Board) AIPlayer.this.board.clone();
+			Board		board	= new Board(this.board);
 			List<Move>	moves	= board.getMoves(color);
 
 			/*
@@ -63,7 +64,7 @@ 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,
+				processors.add(new MoveProcessor(new Board(board), moves.subList(beginIndex, endIndex), color,
 						maxDepth, alphaBetaThreshold));
 				beginIndex = endIndex;
 			}

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

@@ -24,10 +24,10 @@ public class MoveProcessor implements Callable<ProcessingResult> {
 	private Move bestMove;
 
 	public MoveProcessor(Board board, List<Move> rootMoves, Color color, int maxDepth, int alphaBetaThreshold) {
-		this.board		= board;
+		this.board				= board;
-		this.rootMoves	= rootMoves;
+		this.rootMoves			= rootMoves;
-		this.color		= color;
+		this.color				= color;
-		this.maxDepth	= maxDepth;
+		this.maxDepth			= maxDepth;
 		this.alphaBetaThreshold	= alphaBetaThreshold;
 	}
 
@@ -41,9 +41,9 @@ public class MoveProcessor implements Callable<ProcessingResult> {
 		int bestValue = Integer.MIN_VALUE;
 		for (Move move : moves) {
 			board.move(move);
-			int		teamValue		= board.evaluate(color);
+			int	teamValue	= board.evaluate(color);
-			int		enemyValue		= board.evaluate(color.opposite());
+			int	enemyValue	= board.evaluate(color.opposite());
-			int		valueChange		= teamValue - enemyValue;
+			int	valueChange	= teamValue - enemyValue;
 
 			if (depth < maxDepth && valueChange >= alphaBetaThreshold)
 				valueChange -= miniMax(board, board.getMoves(color.opposite()), color.opposite(), depth + 1);

src/dev/kske/chess/uci/UCIHandle.java

@@ -0,0 +1,143 @@
+package dev.kske.chess.uci;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>UCIHandle.java</strong><br>
+ * Created: <strong>18.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class UCIHandle {
+
+	private final Process		process;
+	private final PrintWriter	out;
+	private final UCIReceiver	receiver;
+
+	public UCIHandle(String enginePath) throws IOException {
+		process		= new ProcessBuilder(enginePath).start();
+		out			= new PrintWriter(process.getOutputStream(), true);
+		receiver	= new UCIReceiver(process.getInputStream());
+	}
+
+	public void start() {
+		new Thread(receiver, "UCI Receiver").start();
+		uci();
+	}
+
+	/**
+	 * Tells the engine to use UCI.
+	 */
+	public void uci() {
+		out.println("uci");
+	}
+
+	/**
+	 * Switches the debug mode of the engine on or off.
+	 * 
+	 * @param debug Enables debugging if set to {@code true}, disables it otherwise
+	 */
+	public void debug(boolean debug) {
+		out.println("debug " + (debug ? "on" : "off"));
+	}
+
+	/**
+	 * Synchronized the engine with the GUI
+	 */
+	public void isready() {
+		out.println("isready");
+	}
+
+	/**
+	 * Signifies a button press to the engine.
+	 * 
+	 * @param name The name of the button
+	 */
+	public void setOption(String name) {
+		out.println("setoption name " + name);
+	}
+
+	/**
+	 * Changes an internal parameter of the engine.
+	 * 
+	 * @param name  The name of the parameter
+	 * @param value The value of the parameter
+	 */
+	public void setOption(String name, String value) {
+		out.printf("setoption name %s value %s%n", name, value);
+	}
+
+	/**
+	 * Registers the engine
+	 * 
+	 * @param name The name the engine should be registered with
+	 * @param code The code the engine should be registered with
+	 */
+	public void register(String name, String code) {
+		out.printf("register %s %s%n", name, code);
+	}
+
+	/**
+	 * Tells the engine to postpone the registration.
+	 */
+	public void registerLater() {
+		out.println("register later");
+	}
+
+	/**
+	 * Tells the engine that the next search will be from a different game.
+	 */
+	public void uciNewGame() {
+		out.println("ucinewgame");
+	}
+
+	// TODO: position
+
+	/**
+	 * Sets up the position in its initial state.
+	 */
+	public void startPosition() {
+		out.println("position startpos");
+	}
+
+	/**
+	 * Sets up the position described in the FEN string.
+	 * 
+	 * @param fen FEN representation of the current board
+	 */
+	public void positionFEN(String fen) {
+		out.println("position fen " + fen);
+	}
+
+	// TODO: go with parameters
+
+	public void go() {
+		out.println("go");
+	}
+
+	/**
+	 * Stops calculation as soon as possible.
+	 */
+	public void stop() {
+		out.println("stop");
+	}
+
+	/**
+	 * Tells the engine that the user has played the expected move.
+	 */
+	public void ponderHit() {
+		out.println("ponderhit");
+	}
+
+	/**
+	 * Quits the engine process as soon as possible.
+	 */
+	public void quit() {
+		out.println("quit");
+	}
+
+	public void setListener(UCIListener listener) {
+		receiver.addListener(listener);
+	}
+}

src/dev/kske/chess/uci/UCIInfo.java

@@ -0,0 +1,198 @@
+package dev.kske.chess.uci;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import dev.kske.chess.board.Move;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>UCIInfo.java</strong><br>
+ * Created: <strong>28.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class UCIInfo {
+
+	private int			depth, seldepth, time, nodes, multipv, currmovenumber, hashfull, nps, tbhits, sbhits, cpuload,
+			cpunr;
+	private List<Move>	pv, refutation, currline;
+	private Move		currmove;
+	private Score		score;
+	private String		displayString;
+
+	/**
+	 * Contains every parameter for the UCI info command. Helpful for parsing
+	 * multi-value parameters.
+	 */
+	private static final List<String> params = Arrays.asList("depth",
+			"seldepth",
+			"time",
+			"nodes",
+			"multipv",
+			"currmove",
+			"currmovenumber",
+			"hashfull",
+			"nps",
+			"tbhits",
+			"sbhits",
+			"cpuload",
+			"string",
+			"score",
+			"pv",
+			"refutation",
+			"currline");
+
+	public UCIInfo(String line) {
+		pv			= new ArrayList<>();
+		refutation	= new ArrayList<>();
+		currline	= new ArrayList<>();
+		String[] tokens = line.split(" ");
+
+		for (int i = 0; i < tokens.length; i++)
+			switch (tokens[i]) {
+				// Single parameter info
+				case "depth":
+					depth = Integer.parseInt(tokens[++i]);
+					break;
+				case "seldepth":
+					seldepth = Integer.parseInt(tokens[++i]);
+					break;
+				case "time":
+					time = Integer.parseInt(tokens[++i]);
+					break;
+				case "nodes":
+					nodes = Integer.parseInt(tokens[++i]);
+					break;
+				case "multipv":
+					multipv = Integer.parseInt(tokens[++i]);
+					break;
+				case "currmove":
+					currmove = Move.fromSAN(tokens[++i]);
+					break;
+				case "currmovenumber":
+					currmovenumber = Integer.parseInt(tokens[++i]);
+					break;
+				case "hashfull":
+					hashfull = Integer.parseInt(tokens[++i]);
+					break;
+				case "nps":
+					nps = Integer.parseInt(tokens[++i]);
+					break;
+				case "tbhits":
+					tbhits = Integer.parseInt(tokens[++i]);
+					break;
+				case "sbhits":
+					sbhits = Integer.parseInt(tokens[++i]);
+					break;
+				case "cpuload":
+					cpuload = Integer.parseInt(tokens[++i]);
+					break;
+				case "string":
+					displayString = tokens[++i];
+					break;
+				case "score":
+					score = new Score(line.substring(line.indexOf("score") + tokens[i].length() + 1));
+					i += score.getLength() + 1;
+					break;
+				case "pv":
+					while (++i < tokens.length && !params.contains(tokens[i]))
+						pv.add(Move.fromSAN(tokens[i]));
+					break;
+				case "refutation":
+					while (++i < tokens.length && !params.contains(tokens[i]))
+						refutation.add(Move.fromSAN(tokens[i]));
+					break;
+				// TODO: currline
+				case "currline":
+					while (++i < tokens.length && !params.contains(tokens[i]))
+						;
+					System.err.println("The parameter 'currline' for command 'info' is not yet implemented");
+					break;
+				default:
+					System.err.printf("Unknown parameter '%s' for command 'info' found!%n", tokens[i]);
+			}
+	}
+
+	public int getDepth() { return depth; }
+
+	public int getSeldepth() { return seldepth; }
+
+	public int getTime() { return time; }
+
+	public int getNodes() { return nodes; }
+
+	public int getMultipv() { return multipv; }
+
+	public int getCurrmovenumber() { return currmovenumber; }
+
+	public int getHashfull() { return hashfull; }
+
+	public int getNps() { return nps; }
+
+	public int getTbhits() { return tbhits; }
+
+	public int getSbhits() { return sbhits; }
+
+	public int getCpuload() { return cpuload; }
+
+	public int getCpunr() { return cpunr; }
+
+	public List<Move> getPv() { return pv; }
+
+	public List<Move> getRefutation() { return refutation; }
+
+	public List<Move> getCurrline() { return currline; }
+
+	public Move getCurrmove() { return currmove; }
+
+	public Score getScore() { return score; }
+
+	public String getDisplayString() { return displayString; }
+
+	public static class Score {
+
+		private int		cp, mate;
+		private boolean	lowerbound, upperbound;
+		private int		length;
+
+		public Score(String line) {
+			String[]	tokens	= line.split(" ");
+			int			i		= 0;
+			for (; i < tokens.length; i++) {
+				if (params.contains(tokens[i])) break;
+				switch (tokens[i]) {
+					case "cp":
+						cp = Integer.parseInt(tokens[++i]);
+						break;
+					case "mate":
+						mate = Integer.parseInt(tokens[++i]);
+						break;
+					case "lowerbound":
+						lowerbound = true;
+						break;
+					case "upperbound":
+						upperbound = true;
+						break;
+					default:
+						System.err.printf("Unknown parameter '%s' for command 'score' found!%n", tokens[i]);
+				}
+			}
+			length = i + 1;
+		}
+
+		public int getCp() { return cp; }
+
+		public int getMate() { return mate; }
+
+		public boolean isLowerbound() { return lowerbound; }
+
+		public boolean isUpperbound() { return upperbound; }
+
+		/**
+		 * @return The number of tokens this 'score' command contains (including
+		 *         itself).
+		 */
+		public int getLength() { return length; }
+	}
+}

src/dev/kske/chess/uci/UCIListener.java

@@ -0,0 +1,94 @@
+package dev.kske.chess.uci;
+
+import dev.kske.chess.board.Move;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>UCIListener.java</strong><br>
+ * Created: <strong>19.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public interface UCIListener {
+
+	/**
+	 * Identifies the name of the engine.
+	 * 
+	 * @param name The name of the engine
+	 */
+	default void onIdName(String name) {}
+
+	/**
+	 * Identifies the author of the engine.
+	 * 
+	 * @param author The name of the engine's author
+	 */
+	default void onIdAuthor(String author) {}
+
+	/**
+	 * The engine is ready in UCI mode.
+	 */
+	default void onUCIOk() {}
+
+	/**
+	 * The engine has processed all inputs and is ready for new commands.
+	 */
+	default void onReadyOk() {}
+
+	/**
+	 * The engine has stopped searching and has found the best move.
+	 * 
+	 * @param move The best moves the engine has found
+	 */
+	default void onBestMove(String move) {}
+
+	/**
+	 * The engine has stopped searching and has found the best move.
+	 * 
+	 * @param move       The best move the engine has found
+	 * @param ponderMove The move the engine likes to ponder on
+	 */
+	default void onBestMove(String move, Move ponderMove) {}
+
+	/**
+	 * The engine will check the copy protection now.
+	 */
+	default void onCopyProtectionChecking() {}
+	/**
+	 * The engine has successfully checked the copy protection.
+	 */
+	default void onCopyProtectionOk() {}
+
+	/**
+	 * The engine has encountered an error during copy protection checking.
+	 */
+	default void onCopyProtectionError() {}
+
+	/**
+	 * The engine will check the registration now.
+	 */
+	default void onRegistrationChecking() {}
+
+	/**
+	 * The engine has successfully checked the registration.
+	 */
+	default void onRegistrationOk() {}
+
+	/**
+	 * The engine has encountered an error during registration checking.
+	 */
+	default void onRegistrationError() {}
+
+	/**
+	 * The engine sends information to the GUI.
+	 * 
+	 * @param info Contains all pieces of information to be sent
+	 */
+	default void onInfo(UCIInfo info) {}
+
+	/**
+	 * Tells the GUI which parameters can be changed in the engine.
+	 * 
+	 * @param option Option object describing the parameter
+	 */
+	default void onOption(UCIOption option) {}
+}

src/dev/kske/chess/uci/UCIOption.java

@@ -0,0 +1,68 @@
+package dev.kske.chess.uci;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.StringJoiner;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>UCIOption.java</strong><br>
+ * Created: <strong>22.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class UCIOption {
+
+	private String			name, defaultVal, minVal, maxVal;
+	private GUIType			type;
+	private List<String>	varList;
+
+	public UCIOption(String line) {
+		varList = new ArrayList<>();
+		String[] tokens = line.split(" ");
+
+		for (int i = 0; i < tokens.length; i++)
+			switch (tokens[i]) {
+				case "name":
+					StringJoiner nameJoiner = new StringJoiner(" ");
+					while (!Arrays.asList("type", "default", "min", "max", "var").contains(tokens[i + 1]))
+						nameJoiner.add(tokens[++i]);
+					name = nameJoiner.toString();
+					break;
+				case "type":
+					type = GUIType.valueOf(tokens[++i].toUpperCase());
+					break;
+				case "default":
+					// Default string may be empty
+					defaultVal = i == tokens.length - 1 ? "" : tokens[++i];
+					break;
+				case "min":
+					minVal = tokens[++i];
+					break;
+				case "max":
+					maxVal = tokens[++i];
+					break;
+				case "var":
+					varList.add(tokens[++i]);
+					break;
+				default:
+					System.err.printf("Unknown parameter '%s' for command 'option' found!%n", tokens[i]);
+			}
+	}
+
+	public String getName() { return name; }
+
+	public String getDefaultVal() { return defaultVal; }
+
+	public String getMinVal() { return minVal; }
+
+	public String getMaxVal() { return maxVal; }
+
+	public GUIType getType() { return type; }
+
+	public List<String> getVarList() { return varList; }
+
+	public static enum GUIType {
+		CHECK, SPIN, COMBO, BUTTON, STRING
+	}
+}

src/dev/kske/chess/uci/UCIReceiver.java

@@ -0,0 +1,143 @@
+package dev.kske.chess.uci;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.List;
+
+import dev.kske.chess.board.Move;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>UCIReceiver.java</strong><br>
+ * Created: <strong>19.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class UCIReceiver implements Runnable {
+
+	private final BufferedReader in;
+
+	private List<UCIListener> listeners;
+
+	public UCIReceiver(InputStream in) {
+		this.in		= new BufferedReader(new InputStreamReader(in));
+		listeners	= new ArrayList<>();
+	}
+
+	@Override
+	public void run() {
+		String line;
+		while (!Thread.currentThread().isInterrupted())
+			try {
+				if ((line = in.readLine()) != null && !line.isEmpty()) parse(line);
+			} catch (IndexOutOfBoundsException ex) {
+				System.err.println("Too few arguments were provided!");
+				ex.printStackTrace();
+			} catch (IOException ex) {
+				ex.printStackTrace();
+			}
+	}
+
+	private void parse(String line) {
+		int		spaceIndex	= line.indexOf(' ');
+		String	command		= spaceIndex == -1 ? line : line.substring(0, spaceIndex);
+		switch (command) {
+			case "id":
+				parseId(line.substring(command.length() + 1));
+				break;
+			case "uciok":
+				listeners.forEach(UCIListener::onUCIOk);
+				break;
+			case "readyok":
+				listeners.forEach(UCIListener::onReadyOk);
+				break;
+			case "bestmove":
+				parseBestMove(line.substring(command.length() + 1));
+				break;
+			case "copyprotection":
+				parseCopyProtection(line.substring(command.length() + 1));
+				break;
+			case "registration":
+				parseRegistration(line.substring(command.length() + 1));
+				break;
+			case "info":
+				parseInfo(line.substring(command.length() + 1));
+				break;
+			case "option":
+				parseOption(line.substring(command.length() + 1));
+				break;
+			default:
+				System.err.printf("Unknown command '%s' found!%n", command);
+		}
+	}
+
+	private void parseId(String line) {
+		String	param	= line.substring(0, line.indexOf(' '));
+		String	arg		= line.substring(param.length() + 1);
+		switch (param) {
+			case "name":
+				listeners.forEach(l -> l.onIdName(arg));
+				break;
+			case "author":
+				listeners.forEach(l -> l.onIdAuthor(arg));
+				break;
+			default:
+				System.err.printf("Unknown parameter '%s' for command 'id' found!%n", param);
+		}
+	}
+
+	private void parseBestMove(String line) {
+		String[]	tokens	= line.split(" ");
+		String		move	= tokens[0];
+
+		// Ponder move
+		if (tokens.length == 3) listeners.forEach(l -> l.onBestMove(move, Move.fromSAN(tokens[2])));
+		else listeners.forEach(l -> l.onBestMove(move));
+	}
+
+	private void parseCopyProtection(String line) {
+		switch (line) {
+			case "checking":
+				listeners.forEach(UCIListener::onCopyProtectionChecking);
+				break;
+			case "ok":
+				listeners.forEach(UCIListener::onCopyProtectionOk);
+				break;
+			case "error":
+				listeners.forEach(UCIListener::onCopyProtectionError);
+				break;
+			default:
+				System.err.printf("Unknown parameter '%s' for command 'copyprotection' found!%n", line);
+		}
+	}
+
+	private void parseRegistration(String line) {
+		switch (line) {
+			case "checking":
+				listeners.forEach(UCIListener::onRegistrationChecking);
+				break;
+			case "ok":
+				listeners.forEach(UCIListener::onRegistrationOk);
+				break;
+			case "error":
+				listeners.forEach(UCIListener::onRegistrationError);
+				break;
+			default:
+				System.err.printf("Unknown parameter '%s' for command 'registration' found!%n", line);
+		}
+	}
+
+	private void parseInfo(String line) {
+		listeners.forEach(l -> l.onInfo(new UCIInfo(line)));
+	}
+
+	private void parseOption(String line) {
+		listeners.forEach(l -> l.onOption(new UCIOption((line))));
+	}
+
+	public void addListener(UCIListener listener) {
+		listeners.add(listener);
+	}
+}

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

@@ -78,5 +78,4 @@ public class AIConfigDialog extends JDialog {
 	public boolean isStartGame() { return startGame; }
 
 	public void setStartGame(boolean startGame) { this.startGame = startGame; }
-
 }

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

@@ -1,8 +1,6 @@
 package dev.kske.chess.ui;
 
 import java.awt.Dimension;
-import java.awt.event.ComponentAdapter;
-import java.awt.event.ComponentEvent;
 
 import javax.swing.JLayeredPane;
 
@@ -24,23 +22,13 @@ public class BoardPane extends JLayeredPane {
 	public BoardPane() {
 		boardComponent		= new BoardComponent(this);
 		overlayComponent	= new OverlayComponent(this);
+		setLayer(overlayComponent, 1);
+		setLayout(null);
 
-		add(boardComponent, Integer.valueOf(1));
+		add(boardComponent);
-		add(overlayComponent, Integer.valueOf(2));
+		add(overlayComponent);
 
-		/*
+		tileSize = 60;
-		 * Add a component listener for adjusting the tile size on resizing.
-		 * The size of the board is assumed to be 8x8, as well as the both the board and
-		 * the tiles being square.
-		 */
-		addComponentListener(new ComponentAdapter() {
-
-			@Override
-			public void componentResized(ComponentEvent e) {
-				tileSize = getWidth() / 8;
-				TextureUtil.scalePieceTextures(tileSize);
-			}
-		});
 		setSize(getPreferredSize());
 	}
 

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

@@ -0,0 +1,98 @@
+package dev.kske.chess.ui;
+
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.List;
+
+import dev.kske.chess.uci.UCIHandle;
+import dev.kske.chess.uci.UCIListener;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>MenuBar.java</strong><br>
+ * Created: <strong>23.07.2019</strong><br>
+ * Author: <strong>Leon Hofmeister</strong>
+ */
+public class EngineUtil {
+
+	private static volatile List<EngineInfo> engineInfos;
+
+	private static final String engineInfoFile = "engine_infos.ser";
+
+	static {
+		loadEngineInfos();
+	}
+
+	private EngineUtil() {}
+
+	public static void addEngine(String enginePath) {
+		try {
+			EngineInfo	info	= new EngineInfo(enginePath);
+			UCIHandle	handle	= new UCIHandle(enginePath);
+			handle.setListener(new UCIListener() {
+
+				@Override
+				public void onIdName(String name) {
+					info.name = name;
+				}
+
+				@Override
+				public void onIdAuthor(String author) {
+					info.author = author;
+				}
+
+				@Override
+				public void onUCIOk() {
+					engineInfos.add(info);
+					handle.quit();
+					saveEngineInfos();
+				}
+			});
+			handle.start();
+		} catch (IOException ex) {
+			ex.printStackTrace();
+		}
+	}
+
+	@SuppressWarnings("unchecked")
+	private static void loadEngineInfos() {
+		try (ObjectInputStream in = new ObjectInputStream(new FileInputStream(engineInfoFile))) {
+			Object obj = in.readObject();
+			if (obj instanceof ArrayList<?>) engineInfos = (ArrayList<EngineInfo>) obj;
+			else throw new IOException("Serialized object has the wrong class.");
+		} catch (ClassNotFoundException | IOException ex) {
+			engineInfos = new ArrayList<>();
+		}
+	}
+
+	private static void saveEngineInfos() {
+		try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(engineInfoFile))) {
+			out.writeObject(engineInfos);
+		} catch (IOException ex) {
+			ex.printStackTrace();
+		}
+	}
+
+	public static class EngineInfo implements Serializable {
+
+		private static final long serialVersionUID = -474177108900833005L;
+
+		public String path, name, author;
+
+		public EngineInfo(String path) {
+			this.path = path;
+		}
+
+		@Override
+		public String toString() {
+			return name + " by " + author + " at " + path;
+		}
+	}
+
+	public static List<EngineInfo> getEngineInfos() { return engineInfos; }
+}

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

@@ -0,0 +1,55 @@
+package dev.kske.chess.ui;
+
+import java.awt.datatransfer.DataFlavor;
+import java.awt.datatransfer.UnsupportedFlavorException;
+import java.awt.dnd.DnDConstants;
+import java.awt.dnd.DropTargetAdapter;
+import java.awt.dnd.DropTargetDropEvent;
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.List;
+
+import dev.kske.chess.game.Game;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>FENDropTarget.java</strong><br>
+ * Created: <strong>13 Aug 2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class FENDropTarget extends DropTargetAdapter {
+
+	private MainWindow mainWindow;
+
+	public FENDropTarget(MainWindow mainWindow) {
+		this.mainWindow = mainWindow;
+	}
+
+	@SuppressWarnings("unchecked")
+	@Override
+	public void drop(DropTargetDropEvent evt) {
+		try {
+			evt.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
+			((List<File>) evt.getTransferable().getTransferData(DataFlavor.javaFileListFlavor)).forEach(file -> {
+				try (BufferedReader br = new BufferedReader(new FileReader(file))) {
+					final GamePane	gamePane	= mainWindow.addGamePane();
+					final String	fen			= br.readLine();
+					GameConfigurationDialog.show((whiteName, blackName) -> {
+						final Game game = new Game(gamePane.getBoardPane(), whiteName, blackName, fen);
+						gamePane.setGame(game);
+						game.start();
+					});
+					evt.dropComplete(true);
+				} catch (IOException e) {
+					e.printStackTrace();
+					evt.rejectDrop();
+				}
+			});
+		} catch (UnsupportedFlavorException | IOException ex) {
+			ex.printStackTrace();
+			evt.rejectDrop();
+		}
+	}
+}

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

@@ -0,0 +1,76 @@
+package dev.kske.chess.ui;
+
+import java.awt.Font;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.function.BiConsumer;
+
+import javax.swing.DefaultComboBoxModel;
+import javax.swing.JButton;
+import javax.swing.JComboBox;
+import javax.swing.JDialog;
+import javax.swing.JLabel;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>GameConfigurationDialog.java</strong><br>
+ * Created: <strong>24.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class GameConfigurationDialog {
+
+	private GameConfigurationDialog() {}
+
+	public static void show(BiConsumer<String, String> action) {
+		new JDialog() {
+
+			private static final long serialVersionUID = -5768339760489440385L;
+
+			{
+				setTitle("Game Configuration");
+				setBounds(100, 100, 281, 142);
+				setModal(true);
+				setLocationRelativeTo(null);
+				getContentPane().setLayout(null);
+
+				List<String> options = new ArrayList<>(Arrays.asList("Natural Player", "AI Player"));
+				EngineUtil.getEngineInfos().forEach(info -> options.add(info.name));
+
+				JLabel lblWhite = new JLabel("White:");
+				lblWhite.setFont(new Font("Tahoma", Font.PLAIN, 14));
+				lblWhite.setBounds(10, 11, 49, 14);
+				getContentPane().add(lblWhite);
+
+				JComboBox<Object> cbWhite = new JComboBox<>();
+				cbWhite.setModel(new DefaultComboBoxModel<Object>(options.toArray()));
+				cbWhite.setBounds(98, 9, 159, 22);
+				getContentPane().add(cbWhite);
+
+				JLabel lblBlack = new JLabel("Black:");
+				lblBlack.setFont(new Font("Tahoma", Font.PLAIN, 14));
+				lblBlack.setBounds(10, 38, 49, 14);
+				getContentPane().add(lblBlack);
+
+				JComboBox<Object> cbBlack = new JComboBox<>();
+				cbBlack.setModel(new DefaultComboBoxModel<Object>(options.toArray()));
+				cbBlack.setBounds(98, 36, 159, 22);
+				getContentPane().add(cbBlack);
+
+				JButton btnStart = new JButton("Start");
+				btnStart.addActionListener((evt) -> {
+					dispose();
+					action.accept(options.get(cbWhite.getSelectedIndex()), options.get(cbBlack.getSelectedIndex()));
+				});
+				btnStart.setBounds(20, 73, 89, 23);
+				getContentPane().add(btnStart);
+
+				JButton btnCancel = new JButton("Cancel");
+				btnCancel.addActionListener((evt) -> dispose());
+				btnCancel.setBounds(157, 73, 89, 23);
+				getContentPane().add(btnCancel);
+
+			}
+		}.setVisible(true);
+	}
+}

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

@@ -0,0 +1,126 @@
+package dev.kske.chess.ui;
+
+import java.awt.GridBagConstraints;
+import java.awt.GridBagLayout;
+import java.awt.GridLayout;
+
+import javax.swing.JButton;
+import javax.swing.JComponent;
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+
+import dev.kske.chess.board.Piece.Color;
+import dev.kske.chess.game.Game;
+import dev.kske.chess.game.NaturalPlayer;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>GamePane.java</strong><br>
+ * Created: <strong>23.08.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class GamePane extends JComponent {
+
+	private static final long serialVersionUID = 4349772338239617477L;
+
+	private JButton		btnRestart, btnSwapColors;
+	private BoardPane	boardPane;
+	private LogPanel	logPanel;
+	private Game		game;
+	private Color		activeColor;
+
+	public GamePane() {
+		activeColor = Color.WHITE;
+
+		GridBagLayout gridBagLayout = new GridBagLayout();
+		gridBagLayout.columnWidths	= new int[] { 450, 1, 0 };
+		gridBagLayout.rowHeights	= new int[] { 33, 267, 1, 0 };
+		gridBagLayout.columnWeights	= new double[] { 0.0, 0.0, Double.MIN_VALUE };
+		gridBagLayout.rowWeights	= new double[] { 0.0, 0.0, 0.0, Double.MIN_VALUE };
+		setLayout(gridBagLayout);
+
+		JPanel toolPanel = new JPanel();
+		btnRestart = new JButton("Restart");
+		btnRestart.addActionListener((evt) -> { if (game != null) game.reset(); game.start(); });
+
+		btnSwapColors = new JButton("Play as black");
+		btnSwapColors.addActionListener((evt) -> {
+			game.swapColors();
+			btnSwapColors.setText("Play as " + activeColor.toString().toLowerCase());
+			activeColor = activeColor.opposite();
+		});
+
+		toolPanel.add(btnRestart);
+		toolPanel.add(btnSwapColors);
+
+		GridBagConstraints gbc_toolPanel = new GridBagConstraints();
+		gbc_toolPanel.anchor	= GridBagConstraints.NORTH;
+		gbc_toolPanel.fill		= GridBagConstraints.HORIZONTAL;
+		gbc_toolPanel.gridx		= 0;
+		gbc_toolPanel.gridy		= 0;
+		add(toolPanel, gbc_toolPanel);
+		boardPane = new BoardPane();
+		GridBagConstraints gbc_boardPane = new GridBagConstraints();
+		gbc_boardPane.fill	= GridBagConstraints.BOTH;
+		gbc_boardPane.gridx	= 0;
+		gbc_boardPane.gridy	= 1;
+		add(boardPane, gbc_boardPane);
+
+		JPanel				numberPanel		= new JPanel(new GridLayout(8, 1));
+		GridBagConstraints	gbc_numberPanel	= new GridBagConstraints();
+		gbc_numberPanel.anchor	= GridBagConstraints.WEST;
+		gbc_numberPanel.fill	= GridBagConstraints.VERTICAL;
+		gbc_numberPanel.gridx	= 1;
+		gbc_numberPanel.gridy	= 1;
+		add(numberPanel, gbc_numberPanel);
+
+		JPanel				letterPanel		= new JPanel(new GridLayout(1, 8));
+		GridBagConstraints	gbc_letterPanel	= new GridBagConstraints();
+		gbc_letterPanel.anchor	= GridBagConstraints.NORTH;
+		gbc_letterPanel.fill	= GridBagConstraints.HORIZONTAL;
+		gbc_letterPanel.gridx	= 0;
+		gbc_letterPanel.gridy	= 2;
+		add(letterPanel, gbc_letterPanel);
+
+		// Initialize board coordinates
+		for (int i = 0; i < 8; i++) {
+			numberPanel.add(new JLabel(String.valueOf(8 - i)));
+			JLabel letterLabel = new JLabel(String.valueOf((char) (65 + i)));
+			letterLabel.setHorizontalAlignment(JLabel.CENTER);
+			letterPanel.add(letterLabel);
+		}
+
+		// Initialize LogPanel
+		logPanel = new LogPanel();
+		GridBagConstraints gbc_logPanel = new GridBagConstraints();
+		gbc_logPanel.anchor	= GridBagConstraints.EAST;
+		gbc_logPanel.fill	= GridBagConstraints.VERTICAL;
+		gbc_logPanel.gridx	= 2;
+		gbc_logPanel.gridy	= 1;
+		add(logPanel, gbc_logPanel);
+	}
+
+	/**
+	 * @return The {@link BoardPane} instance associated with this game pane
+	 */
+	public BoardPane getBoardPane() { return boardPane; }
+
+	/**
+	 * @return The {@link Game} instance associated with this game pane
+	 */
+	public Game getGame() { return game; }
+
+	/**
+	 * Assigns a new {@link Game} instance to this game pane. If exactly one of the
+	 * players is natural, color swapping functionality is enabled.
+	 * 
+	 * @param game The {@link Game} to assign to this game pane.
+	 */
+	public void setGame(Game game) {
+		if (this.game != null) this.game.stop();
+		this.game = game;
+		btnSwapColors.setEnabled(game.getPlayers().get(Color.WHITE) instanceof NaturalPlayer
+				^ game.getPlayers().get(Color.BLACK) instanceof NaturalPlayer);
+		logPanel.setLog(game.getBoard().getLog());
+	}
+}

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

@@ -0,0 +1,76 @@
+package dev.kske.chess.ui;
+
+import java.awt.BorderLayout;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import javax.swing.JPanel;
+import javax.swing.JScrollPane;
+import javax.swing.JTable;
+import javax.swing.border.EmptyBorder;
+import javax.swing.table.DefaultTableModel;
+
+import dev.kske.chess.board.Log;
+import dev.kske.chess.board.Log.MoveNode;
+import dev.kske.chess.event.Event;
+import dev.kske.chess.event.EventBus;
+import dev.kske.chess.event.MoveEvent;
+import dev.kske.chess.event.Subscribable;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>LogPanel.java</strong><br>
+ * Created: <strong>17.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class LogPanel extends JPanel implements Subscribable {
+
+	private static final long serialVersionUID = 1932671698254197119L;
+
+	private JTable	mtable;
+
+	private Log log;
+
+	/**
+	 * Create the frame.
+	 */
+	public LogPanel() {
+		setBorder(new EmptyBorder(5, 5, 5, 5));
+		setLayout(new BorderLayout(0, 0));
+
+		mtable = new JTable();
+		mtable.setEnabled(false);
+		add(new JScrollPane(mtable), BorderLayout.CENTER);
+
+		EventBus.getInstance().register(this);
+	}
+
+	@Override
+	public Set<Class<?>> supports() {
+		return new HashSet<>(Arrays.asList(MoveEvent.class));
+	}
+
+	@Override
+	public void handle(Event<?> event) {
+		if (log == null) return;
+
+		// TODO: Display log with variations
+		final List<MoveNode>	moves	= /* log.getLoggedMoves() */ new ArrayList<>();
+		String[][]				data	= new String[moves.size() / 2 + moves.size() % 2][2];
+		for (int i = 0; i < data.length; i++) {
+			data[i][0] = moves.get(i * 2).move.toSAN();
+			if (i * 2 + 1 < moves.size()) data[i][1] = moves.get(i * 2 + 1).move.toSAN();
+		}
+		mtable.setModel(new DefaultTableModel(data, new String[] { "White", "Black" }));
+	}
+
+	public Log getLog() { return log; }
+
+	public void setLog(Log log) {
+		this.log = log;
+		handle(null);
+	}
+}

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

@@ -1,14 +1,11 @@
 package dev.kske.chess.ui;
 
-import java.awt.BorderLayout;
 import java.awt.EventQueue;
 import java.awt.Toolkit;
+import java.awt.dnd.DropTarget;
 
-import javax.swing.JButton;
 import javax.swing.JFrame;
-import javax.swing.JPanel;
+import javax.swing.JTabbedPane;
-
-import dev.kske.chess.game.Game;
 
 /**
  * Project: <strong>Chess</strong><br>
@@ -16,25 +13,21 @@ import dev.kske.chess.game.Game;
  * Created: <strong>01.07.2019</strong><br>
  * Author: <strong>Kai S. K. Engelbart</strong>
  */
-public class MainWindow {
+public class MainWindow extends JFrame {
 
-	private JFrame		mframe;
+	private static final long serialVersionUID = -3100939302567978977L;
-	private BoardPane	boardPane;
+
-	private Game		game;
+	private JTabbedPane tabbedPane;
 
 	/**
 	 * Launch the application.
 	 */
 	public static void main(String[] args) {
-		EventQueue.invokeLater(new Runnable() {
+		EventQueue.invokeLater(() -> {
-
+			try {
-			public void run() {
+				new MainWindow();
-				try {
+			} catch (Exception ex) {
-					MainWindow window = new MainWindow();
+				ex.printStackTrace();
-					window.mframe.setVisible(true);
-				} catch (Exception e) {
-					e.printStackTrace();
-				}
 			}
 		});
 	}
@@ -43,6 +36,7 @@ public class MainWindow {
 	 * Create the application.
 	 */
 	public MainWindow() {
+		super("Chess by Kai S. K. Engelbart");
 		initialize();
 	}
 
@@ -50,31 +44,48 @@ public class MainWindow {
 	 * Initialize the contents of the frame.
 	 */
 	private void initialize() {
-		mframe = new JFrame();
+		// Configure frame
-		mframe.setResizable(false);
+		setResizable(false);
-		mframe.setBounds(100, 100, 494, 565);
+		setBounds(100, 100, 494, 565);
-		mframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+		setIconImage(Toolkit.getDefaultToolkit().getImage(getClass().getResource("/pieces/queen_white.png")));
 
-		mframe.setIconImage(Toolkit.getDefaultToolkit().getImage(getClass().getResource("/pieces/king_white.png")));
+		// Add frame content
+		tabbedPane = new JTabbedPane();
+		getContentPane().add(tabbedPane);
 
-		boardPane = new BoardPane();
+		setJMenuBar(new MenuBar(this));
-		mframe.getContentPane().add(boardPane, BorderLayout.CENTER);
+		new DropTarget(this, new FENDropTarget(this));
 
-		mframe.setJMenuBar(new MenuBar(this));
+		// Update position and dimensions
-
+		pack();
-		JPanel toolPanel = new JPanel();
+		setLocationRelativeTo(null);
-		mframe.getContentPane().add(toolPanel, BorderLayout.NORTH);
+		setVisible(true);
-
-		JButton btnRestart = new JButton("Restart");
-		btnRestart.addActionListener((evt) -> { if (game != null) game.reset(); game.start(); });
-		toolPanel.add(btnRestart);
-		mframe.pack();
-		mframe.setLocationRelativeTo(null);
 	}
 
-	public BoardPane getBoardPane() { return boardPane; }
+	/**
+	 * @return The currently selected {@link GamePane} component
+	 */
+	public GamePane getSelectedGamePane() { return (GamePane) tabbedPane.getSelectedComponent(); }
 
-	public Game getGame() { return game; }
+	/**
+	 * Creates a new {@link GamePane}, adds it to the tabbed pane and opens it.
+	 * 
+	 * @return The new {@link GamePane}
+	 */
+	public GamePane addGamePane() {
+		GamePane gamePane = new GamePane();
+		tabbedPane.add("Game " + (tabbedPane.getComponentCount() + 1), gamePane);
+		tabbedPane.setSelectedIndex(tabbedPane.getComponentCount() - 1);
+		return gamePane;
+	}
 
-	public void setGame(Game game) { this.game = game; }
+	/**
+	 * Removes a {@link GamePane} form the tabbed pane.
+	 * 
+	 * @param index The index of the {@link GamePane} to remove
+	 */
+	public void removeGamePane(int index) {
+		tabbedPane.remove(index);
+	}
 }

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

@@ -1,8 +1,12 @@
 package dev.kske.chess.ui;
 
+import java.awt.Toolkit;
+import java.awt.datatransfer.StringSelection;
+
 import javax.swing.JMenu;
 import javax.swing.JMenuBar;
 import javax.swing.JMenuItem;
+import javax.swing.JOptionPane;
 
 import dev.kske.chess.game.Game;
 
@@ -16,49 +20,74 @@ public class MenuBar extends JMenuBar {
 
 	private static final long serialVersionUID = -7221583703531248228L;
 
-	private final MainWindow	mainWindow;
+	private final MainWindow mainWindow;
-	private final BoardPane		boardPane;
 
 	public MenuBar(MainWindow mainWindow) {
-		this.mainWindow	= mainWindow;
+		this.mainWindow = mainWindow;
-		boardPane		= mainWindow.getBoardPane();
 
 		initGameMenu();
+		initEngineMenu();
+		initToolsMenu();
 	}
 
 	private void initGameMenu() {
-		JMenu gameMenu = new JMenu("Game");
+		JMenu		gameMenu		= new JMenu("Game");
+		JMenuItem	newGameMenuItem	= new JMenuItem("New Game");
+		newGameMenuItem.addActionListener((evt) -> {
+			GameConfigurationDialog.show((whiteName, blackName) -> {
+				GamePane	gamePane	= mainWindow.addGamePane();
+				Game		game		= new Game(gamePane.getBoardPane(), whiteName, blackName);
+				gamePane.setGame(game);
+				game.start();
+			});
+		});
+		gameMenu.add(newGameMenuItem);
+		add(gameMenu);
+		newGameMenuItem.doClick();
+	}
 
-		JMenuItem	naturalMenuItem	= new JMenuItem("Game against natural opponent");
+	private void initEngineMenu() {
-		JMenuItem	aiMenuItem		= new JMenuItem("Game against artificial opponent");
+		JMenu engineMenu = new JMenu("Engine");
-		JMenuItem	aiVsAiMenuItem	= new JMenuItem("Watch AI vs. AI");
 
-		naturalMenuItem.addActionListener((evt) -> startGame(Game.createNatural(boardPane)));
+		JMenuItem addEngineMenuItem = new JMenuItem("Add engine");
-
+		addEngineMenuItem.addActionListener((evt) -> {
-		aiMenuItem.addActionListener((evt) -> {
+			String enginePath = JOptionPane.showInputDialog(getParent(),
-			AIConfigDialog dialog = new AIConfigDialog();
+					"Enter the path to a UCI-compatible chess engine:",
-			dialog.setVisible(true);
+					"Engine selection",
-			if (dialog.isStartGame())
+					JOptionPane.QUESTION_MESSAGE);
-				startGame(Game.createNaturalVsAI(boardPane, dialog.getMaxDepth(), dialog.getAlphaBetaThreshold()));
+			if (enginePath != null) EngineUtil.addEngine(enginePath);
 		});
 
-		aiVsAiMenuItem.addActionListener((evt) -> startGame(Game.createAIVsAI(boardPane, 4, 3, -10, -10)));
+		JMenuItem showInfoMenuItem = new JMenuItem("Show engine info");
 
-		gameMenu.add(naturalMenuItem);
+		engineMenu.add(addEngineMenuItem);
-		gameMenu.add(aiMenuItem);
+		engineMenu.add(showInfoMenuItem);
-		gameMenu.add(aiVsAiMenuItem);
+		add(engineMenu);
-
-		add(gameMenu);
-
-		// Start a game
-		naturalMenuItem.doClick();
 	}
 
-	private void startGame(Game game) {
+	private void initToolsMenu() {
-		mainWindow.setGame(game);
+		JMenu toolsMenu = new JMenu("Tools");
 
-		// Update board and board component
+		JMenuItem exportFENMenuItem = new JMenuItem("Export board to FEN");
-		game.reset();
+		exportFENMenuItem.addActionListener((evt) -> {
-		game.start();
+			final String fen = mainWindow.getSelectedGamePane().getGame().getBoard().toFEN();
+			Toolkit.getDefaultToolkit().getSystemClipboard().setContents(new StringSelection(fen), null);
+			JOptionPane.showMessageDialog(mainWindow, String.format("FEN-string copied to clipboard!%n%s", fen));
+		});
+		toolsMenu.add(exportFENMenuItem);
+
+		JMenuItem loadFromFENMenuItem = new JMenuItem("Load board from FEN");
+		loadFromFENMenuItem.addActionListener((evt) -> {
+			final GamePane	gamePane	= mainWindow.addGamePane();
+			final String	fen			= JOptionPane.showInputDialog("Enter a FEN string: ");
+			GameConfigurationDialog.show((whiteName, blackName) -> {
+				final Game game = new Game(gamePane.getBoardPane(), whiteName, blackName, fen);
+				gamePane.setGame(game);
+				game.start();
+			});
+		});
+		toolsMenu.add(loadFromFENMenuItem);
+
+		add(toolsMenu);
 	}
 }

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

@@ -1,5 +1,6 @@
 package dev.kske.chess.ui;
 
+import java.awt.BasicStroke;
 import java.awt.Color;
 import java.awt.Graphics;
 import java.awt.Graphics2D;
@@ -32,8 +33,8 @@ public class OverlayComponent extends JComponent {
 
 	public OverlayComponent(BoardPane boardPane) {
 		this.boardPane = boardPane;
-		setSize(boardPane.getPreferredSize());
 		dots = new ArrayList<>();
+		setSize(boardPane.getPreferredSize());
 	}
 
 	@Override
@@ -42,6 +43,26 @@ public class OverlayComponent extends JComponent {
 
 		final int tileSize = getTileSize();
 
+		// Draw an arrow representing the last move and mark its position and
+		// destination
+		if (arrow != null) {
+			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 g2d = (Graphics2D) g;
+			g2d.setStroke(new BasicStroke(3));
+
+			g2d.setColor(Color.yellow);
+			g2d.drawRect(arrow.pos.x * tileSize, arrow.pos.y * tileSize, tileSize, tileSize);
+			g2d.drawRect(arrow.dest.x * tileSize, arrow.dest.y * tileSize, tileSize, tileSize);
+
+			Shape arrowShape = createArrowShape(pos, dest);
+			g.setColor(new Color(255, 0, 0, 127));
+			g2d.fill(arrowShape);
+			g2d.setColor(Color.black);
+			g2d.draw(arrowShape);
+		}
+
 		// Draw possible moves if a piece was selected
 		if (!dots.isEmpty()) {
 			g.setColor(Color.green);
@@ -52,13 +73,6 @@ 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) {

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

@@ -19,11 +19,9 @@ import dev.kske.chess.board.Piece;
  */
 public class TextureUtil {
 
-	private static Map<String, Image> textures, scaledTextures;
+	private static Map<String, Image> textures = new HashMap<>(), scaledTextures = new HashMap<>();
 
 	static {
-		textures = new HashMap<>();
-		scaledTextures	= new HashMap<>();
 		loadPieceTextures();
 		scaledTextures.putAll(textures);
 	}

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

@@ -1,4 +1,4 @@
-package dev.kske.chess.test;
+package dev.kske.chess.board;
 
 import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertNotSame;
@@ -6,9 +6,7 @@ import static org.junit.Assert.assertNotSame;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import dev.kske.chess.board.Board;
 import dev.kske.chess.board.Piece.Color;
-import dev.kske.chess.board.Queen;
 
 /**
  * Project: <strong>Chess</strong><br>
@@ -33,11 +31,13 @@ class BoardTest {
 	 */
 	@Test
 	void testClone() {
-		Board clone = (Board) board.clone();
+		Board clone = new Board(board);
 		assertNotSame(clone, board);
 		assertNotSame(clone.getBoardArr(), board.getBoardArr());
 
 		clone.getBoardArr()[0][0] = new Queen(Color.BLACK, clone);
+		clone.move(new Move(1, 1, 1, 2));
 		assertNotEquals(clone.getBoardArr()[0][0], board.getBoardArr()[0][0]);
+		assertNotEquals(clone.getLog().getActiveColor(), board.getLog().getActiveColor());
 	}
 }

test/dev/kske/chess/board/LogTest.java

@@ -0,0 +1,165 @@
+package dev.kske.chess.board;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
+
+import org.junit.jupiter.api.Test;
+
+import dev.kske.chess.board.Piece.Color;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>LogTest.java</strong><br>
+ * Created: <strong>13 Sep 2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+class LogTest {
+
+	Log log = new Log();
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#Log()}.
+	 */
+	@Test
+	void testLog() {
+		assertTrue(log.isEmpty());
+		assertNull(log.getLast());
+		assertNull(log.getRoot());
+		assertEquals(log.getActiveColor(), Color.WHITE);
+		assertNull(log.getEnPassant());
+		assertEquals(log.getFullmoveCounter(), 1);
+		assertEquals(log.getHalfmoveClock(), 0);
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#clone()}.
+	 */
+	@Test
+	void testClone() {
+		Log other = new Log(log, false);
+		log.setActiveColor(Color.WHITE);
+		other.setActiveColor(Color.BLACK);
+		assertNotEquals(log.getActiveColor(), other.getActiveColor());
+		log.add(Move.fromSAN("a2a4"), null, true);
+		log.add(Move.fromSAN("a4a5"), null, true);
+		other.add(Move.fromSAN("a2a4"), null, true);
+		other.add(Move.fromSAN("a4a5"), null, true);
+		assertNotEquals(log.getRoot(), other.getRoot());
+		assertNotEquals(log.getRoot().getVariations(), other.getRoot().getVariations());
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#add(dev.kske.chess.board.Move, dev.kske.chess.board.Piece, boolean)}.
+	 */
+	@Test
+	void testAdd() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#removeLast()}.
+	 */
+	@Test
+	void testRemoveLast() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#isEmpty()}.
+	 */
+	@Test
+	void testIsEmpty() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#reset()}.
+	 */
+	@Test
+	void testReset() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#getRoot()}.
+	 */
+	@Test
+	void testGetRoot() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#getLast()}.
+	 */
+	@Test
+	void testGetLast() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#getEnPassant()}.
+	 */
+	@Test
+	void testGetEnPassant() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#setEnPassant(dev.kske.chess.board.Position)}.
+	 */
+	@Test
+	void testSetEnPassant() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#getActiveColor()}.
+	 */
+	@Test
+	void testGetActiveColor() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#setActiveColor(dev.kske.chess.board.Piece.Color)}.
+	 */
+	@Test
+	void testSetActiveColor() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#getFullmoveCounter()}.
+	 */
+	@Test
+	void testGetFullmoveCounter() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#setFullmoveCounter(int)}.
+	 */
+	@Test
+	void testSetFullmoveCounter() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#getHalfmoveClock()}.
+	 */
+	@Test
+	void testGetHalfmoveClock() {
+		fail("Not yet implemented");
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Log#setHalfmoveClock(int)}.
+	 */
+	@Test
+	void testSetHalfmoveClock() {
+		fail("Not yet implemented");
+	}
+}

test/dev/kske/chess/board/PositionTest.java

@@ -0,0 +1,47 @@
+package dev.kske.chess.board;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>PositionTest.java</strong><br>
+ * Created: <strong>24.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+class PositionTest {
+
+	final int	n			= 4;
+	Position[]	positions	= new Position[] { new Position(0, 0), new Position(7, 7), new Position(0, 7), new Position(7, 0) };
+	String[]	sans		= new String[] { "a8", "h1", "a1", "h8" };
+	String[]	strings		= new String[] { "[0, 0]", "[7, 7]", "[0, 7]", "[7, 0]" };
+
+	/**
+	 * Test method for
+	 * {@link dev.kske.chess.board.Position#fromSAN(java.lang.String)}.
+	 */
+	@Test
+	void testFromSAN() {
+		for (int i = 0; i < n; i++)
+			assertEquals(positions[i], Position.fromSAN(sans[i]));
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Position#toSAN()}.
+	 */
+	@Test
+	void testToSAN() {
+		for (int i = 0; i < n; i++)
+			assertEquals(sans[i], positions[i].toSAN());
+	}
+
+	/**
+	 * Test method for {@link dev.kske.chess.board.Position#toString()}.
+	 */
+	@Test
+	void testToString() {
+		for (int i = 0; i < n; i++)
+			assertEquals(strings[i], positions[i].toString());
+	}
+}