static final long serialVersionUID = 250408;

    static final int PIECE = 1;

    static final int QUEEN = 2;

    final Piece white_super_sun = new Piece(new ImgComponent("images/white_super_sun.png").getImage(), "white", QUEEN,

            50);

    final Piece black_super_sun = new Piece(new ImgComponent("images/black_super_sun.png").getImage(), "black", QUEEN,

            50);

    void initBoard() {

        for (int i = 1; i < 8; i += 2)

            add(new ImgComponent("images/black_sun.png").getImage(), i, "black", PIECE);

        for (int i = 8; i < 15; i += 2)

            add(new ImgComponent("images/black_sun.png").getImage(), i, "black", PIECE);

        for (int i = 17; i <= 23; i += 2)

            add(new ImgComponent("images/black_sun.png").getImage(), i, "black", PIECE);

        for (int i = 40; i < 47; i += 2)

            add(new ImgComponent("images/white_sun.png").getImage(), i, "white", PIECE);

        for (int i = 49; i <= 55; i += 2)

            add(new ImgComponent("images/white_sun.png").getImage(), i, "white", PIECE);

        for (int i = 56; i < 63; i += 2)

            add(new ImgComponent("images/white_sun.png").getImage(), i, "white", PIECE);

    }

    /**

     * The init method initializes a complete checkers board with figures and a

     * history.

     */

    public void init() {

        super.init();

        initBoard();

        board_pieces = getPieces();

        repaint();

    }

    public CheckersBoard(int w, int h) {

        super(w, h);

    }

    void add(Image img, int i, String c, int t) {

        int v = 0;

        switch (t) {

        case PIECE:

            v = 10;

        }

        setPiece(i, new Piece(img, c, t, v));

    }

    /**

     * Checks, wether this move is possible or not.

     */

    public boolean validMove(int t, int o) {

        int steps;

        int rows;

        if (t == o)

            return false;

        if (isSamePiece(t, o))

            return false;

        if (getType(o) == EMPTY)

            return false;

        /*

         * 00 01 02 03 04 05 06 07

         * 08 09 10 11 12 13 14 15

         * 16 17 18 19 20 21 22 23

         * 24 25 26 27 28 29 30 31

         * 32 33 34 35 36 37 38 39

         * 40 41 42 43 44 45 46 47

         * 48 49 50 51 52 53 54 55

         * 56 57 58 59 60 61 62 63

         */

        steps = Math.abs(t - o);

        rows = Math.abs(t / 8 - o / 8);

        switch (getType(o)) {

        case PIECE:

            if (steps % 7 == 0) {

                if (steps == 7 && rows == 1 && isEmpty(t)) {

                    if (isBlack(o) && (t > o))

                        return true;

                    if (isWhite(o) && (t < o))

                        return true;

                }

                if (steps == 14 && rows == 2 && isEmpty(t)) {

                    if (isBlack(o) && (t > o) && isEnemy(o + 7, o))

                        return true;

                    if (isWhite(o) && (t < o) && isEnemy(o - 7, o))

                        return true;

                }

            }

            if (steps % 9 == 0) {

                if (steps == 9 && rows == 1 && isEmpty(t)) {

                    if (isBlack(o) && (t > o))

                        return true;

                    if (isWhite(o) && (t < o))

                        return true;

                }

                if (steps == 18 && rows == 2 && isEmpty(t)) {

                    if (isBlack(o) && (t > o) && isEnemy(o + 9, o))

                        return true;

                    if (isWhite(o) && (t < o) && isEnemy(o - 9, o))

                        return true;

                }

            }

            break;

        case QUEEN:

            if (steps % 7 == 0 && isEmpty(t)) {

                if (steps == 7 && rows == 1)

                    return true;

                if (steps == 14 && rows == 2)

                    return true;

                if (steps == 21 && rows == 3)

                    return true;

                if (steps == 28 && rows == 4)

                    return true;

                if (steps == 35 && rows == 5)

                    return true;

                if (steps == 42 && rows == 6)

                    return true;

                if (steps == 49 && rows == 7)

                    return true;

            }

            if (steps % 9 == 0 && isEmpty(t)) {

                if (steps == 9 && rows == 1)

                    return true;

                if (steps == 18 && rows == 2)

                    return true;

                if (steps == 27 && rows == 3)

                    return true;

                if (steps == 36 && rows == 4)

                    return true;

                if (steps == 45 && rows == 5)

                    return true;

                if (steps == 54 && rows == 6)

                    return true;

                if (steps == 63 && rows == 7)

                    return true;

            }

            break;

        }

        return false;

    }

    /**

     * pop: undo the push operation.

     */

    public void undo() {

        History h1 = null;

        History h2 = null;

        int size = stack.size();

        int pos;

        if (size < 2)

            return;

        h1 = stack.elementAt(size - 1);

        h2 = stack.elementAt(size - 2);

        setPiece(h1.pos(), h1.piece());

        setPiece(h2.pos(), h2.piece());

        if (getType(h2.pos()) != EMPTY) {

            pos = 2 * h2.pos() - h1.pos();

            if (pos >= 0 && pos < 64)

                setPiece(pos, new Piece(null, null, EMPTY, 0));

        }

        stack.setSize(size - 2);

        /* Reset the current player */

        setBlacksTurn(h2.turn());

    }

    /**

     * simulates a "valid" move or returns false. all changes are relative to

     * pieces and will not be painted.

     */

    public boolean simulateMove(int t, int o) {

        int rows = Math.abs(t / 8 - o / 8);

        int pos;

        if (!validMove(t, o)) {

            return false;

        }

        if (rows == 2 && getType(o) == PIECE) {

            pos = (t - o) / 2 + o;

            push(getPiece(pos), pos, getPiece(o), o);

            setPiece(pos, new Piece(null, null, EMPTY, 0));

        } else

            push(getPiece(t), t, getPiece(o), o);

        setPiece(t, new Piece(getPiece(o)));

        setPiece(o, new Piece(null, null, EMPTY, 0));

        return true;

    }

    /**

     * performs a "valid" move or returns false. all changes are relative to

     * board_pieces and will be painted.

     */

    public boolean doMove(int t, int o) {

        int steps = Math.abs(t - o);

        int rows = Math.abs(t / 8 - o / 8);

        int pos;

        if (!validMove(t, o)) {

            return false;

        }

        if (rows == 2 && getType(o) == PIECE) {

            pos = (t - o) / 2 + o;

            push(getPiece(pos), pos, getPiece(o), o);

            setPiece(pos, new Piece(null, null, EMPTY, 0));

        } else if (rows >= 2 && getType(o) == QUEEN) {

            if (steps % 7 == 0) {

                if (t > o)

                    for (pos = o + 7; pos <= t - 7; pos += 7) {

                        if (isEnemy(pos, o)) {

                            push(getPiece(pos), pos, getPiece(o), o);

                            setPiece(pos, new Piece(null, null, EMPTY, 0));

                        }

                    }

                else {

                    for (pos = o - 7; pos >= t + 7; pos -= 7) {

                        if (isEnemy(pos, o)) {

                            push(getPiece(pos), pos, getPiece(o), o);

                            setPiece(pos, new Piece(null, null, EMPTY, 0));

                        }

                    }

                }

            }

            if (steps % 9 == 0) {

                if (t > o)

                    for (pos = o + 9; pos <= t - 9; pos += 9) {

                        if (isEnemy(pos, o)) {

                            push(getPiece(pos), pos, getPiece(o), o);

                            setPiece(pos, new Piece(null, null, EMPTY, 0));

                        }

                    }

                else {

                    for (pos = o - 9; pos >= t + 9; pos -= 9) {

                        if (isEnemy(pos, o)) {

                            push(getPiece(pos), pos, getPiece(o), o);

                            setPiece(pos, new Piece(null, null, EMPTY, 0));

                        }

                    }

                }

            }

        }

        if (t <= 7 && getType(o) == PIECE)

            setPiece(t, new Piece(white_super_sun));

        else if (t >= 56 && getType(o) == PIECE)

            setPiece(t, new Piece(black_super_sun));

        else

            setPiece(t, new Piece(getPiece(o)));

        setPiece(o, new Piece(null, null, EMPTY, 0));

        board_pieces = getPieces();

        repaint();

        moveNr = stack.size();

        return true;

    }