通过定时器0来定时显示时间，用按钮来模拟外来脉冲计算小车行驶路程。以及图标的识别-Show time and distance traveled and the car. As well as the icon of the identification

一个按钮，鼠标靠近时，自己变换图标，点击时是另外一个图标-A button, the mouse is near the transform icon, when clicked, the other an icon