I'm sure this chapter has been somewhat enlightening whatever your background is. It gave me a headache writing it! We covered a lot of ground and learned various ways to look at things. For example, we tried an ad hoc collision response algorithm that worked great for a ball bouncing off a rectangle. This technique is perfect for any kind of pong or breakout game. Then we looked more closely at the mathematics of reflection and derived the correct way to do it in general. This is the point of physics modeling in games—and you just learned how to do it.