UFO示例可以通过键盘方向键使飞碟在一个位图背景图像上飞行。如果读者引导飞碟到达游戏屏幕的边缘，那么它将会停止-UFO example direction through the keyboard keys to make a flying saucer in the background bitmap images on the flight. If readers guide the trap to reach the edge of the game screen, then it wil