https://www.pygame.org/docs/ref/rect.html#pygame.Rect
https://blog.csdn.net/YZXnuaa/article/details/79011795
pygame.Rect.clip:
crops a rectangle inside another
https://www.pygame.org/docs/ref/rect.html#pygame.Rect.clip
原文：https://www.cnblogs.com/thebreakofdawn/p/9169135.html