编写一程序画一水平线和圆，并使该圆在该直线上匀速滚动（从屏幕左边滚到屏幕右边）。提示：用sleep（n）函数或定时器实现。 -Write a program to draw a horizontal line and a circle, the circle and make uniform rolling on the line (from the left side of the screen rolled right of the screen). Tip: (n) function