Update 1/9/2013: Fully updated for Cocos2D 2.1-beta4 (original post by Ray Wenderlich, update by Brian Broom). This tutorial helps get you started with Box2D with Cocos2D by showing you how to create a simple app that shows a ball that you can bounce around the screen by rotating your iPhone with the accelerometer. This tutorial is based on an excellent example by Kyle from iPhoneDev.net, but upda