在窗口中显示一个球，该球以与水平成45度夹角作直线运动，当遇到边界时，反弹回来，仍与水平成45度角继续运动。-In the window of a ball, the ball with the level of 45 degrees angle for linear motion, when faced with the border, the rebound came back, still with the level of 45-degree angle to continue to campaign.