Physics engines are what drive popular iOS games like Angry Birds, Stick Golf, Jelly Car, and Stair Dismount. They allow you to create a world that feels more dynamic and lifelike.
Cocos2d is distributed with two physics engines: Box2D and Chipmunk. Both are designed to work only in two dimensions, so they're a perfect fit for cocos2d.
In this chapter, you'll learn the basics of both physics engines, and along the way you'll probably come to appreciate one more than the other. I'll briefly explain the differences between the two physics engines, but for the most part it's a choice based on personal preference.
If you've never worked with a physics engine before, I'll also give you a quick introduction to their basic concepts ...