实现两个同心圆，其中A园大小固定，另外一个B园默认与A园同大，程序开始不会不断缩小，当缩小到直径为0的时候自动放大，当放大到与A园等大的时候，继续缩小，如此循环。按下确定键控制暂停与开始。-Achievement of the two concentric circles, where A garden size is fixed, the other a B and A garden park with a large default, the program will not start shrinking, when reduced to a diameter of 0 when the automatic zoom when you zoom in to a big park with A , to continue to shrink, and so on. Press the OK button to pause and control the start.