public class GamePanel extends JPanel
        implements ActionListener, KeyListener {
    Timer timer = new Timer(16, this);

    public GamePanel() {
        setPreferredSize(new Dimension(700, 520));
        setBackground(new Color(15, 18, 32));
        addKeyListener(this);
        setFocusable(true);
        timer.start();
    }

    public void actionPerformed(ActionEvent e) { update(); repaint(); }
    void update() {}
}