We start our game from the Cocos2D + Box2D template, so it has all the libraries we need. To prepare for this project, we still go through the same motions from the template, namely removing HelloWorldLayer.h/.mm, and changing the references in the IntroLayer.mm to our menu class. There are a couple of additional classes in the template, GLES-Render and PhysicsSprite. We will deal with them later. We also need to switch the supported orientation to portrait only, as we did in the previous chapter. (Don't forget to also remove the background rotation line in the IntroLayer.mm file.)
With a Box2D project, it is important to note that all our implementation classes will need names that end in .mm instead of .m. This tells the compiler that we will be using a mixture of Objective-C and C++. You must do this with Box2D, because Box2D is written in C++. So where do we start?