private void createWindow() {
        JFrame frame = new JFrame();
        frame.setSize(new Dimension(WIDTH*BUTTON_SIZE, HEIGHT*BUTTON_SIZE));
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        for (int x = 0; x < WIDTH; x++) {
            for (int y = 0; y < HEIGHT; y++) {
                frame.add(board.getButton(x, y));
            }
        }

        frame.setLayout(new GridLayout(HEIGHT, WIDTH));
        frame.setVisible(true);
    }