public class Game extends Panel {

  private static class TargetListener
      extends MouseAdapter
  {
    public void mouseEntered(MouseEvent e) {
      oldBG = e.getComponent().getBackground();
      e.getComponent().setBackground(newBG);
    }
    public void mouseExited(MouseEvent e) {
      e.getComponent().setBackground(oldBG);
    }
  }
}