在一个450*350的窗体上在下面放置两个按钮“Start”和“Close”,连续点击“Start”按钮会在窗体上显示多个彩色的小球，分别有红、绿、蓝三种颜色，小球不停的跳跃，碰到窗体的边缘则反弹。单击“Close”按钮则关闭整个程序-in a 450* 350 on the Form placed in the following two button "Start" and "Clos e ", consecutive click on the&quo