private void start() {

/*initialized game elements here */

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        JPanel panel = new JPanel() {
            @Override
            public void paintComponent(Graphics g) {
                /* Drew objects here */
        };

        panel.setPreferredSize(new Dimension(800,600));
        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
        mapKeyStrokesToActions(panel);

        /* Timer */
        timer = new Timer(10, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                updateGame();
                panel.repaint();
            }
        });
        timer.start();
    }

if(gameOver()) {
            frame.getContentPane().removeAll();
            runner.start();
        }