With Inverse Universe, we went back to the drawing board and came out with flying colors! You learned the difference between CCDrawingPrimitives and CCDrawNode. We also extended the CCDrawNode class to create each and every one of our game's elements. We implemented circle-to-circle collision detection and finally understood how tilt controls or the accelerometer work in Cocos2d-x. As a good game design principle, you also learned how to add progression to a game that is not level-based, while still keeping it open-ended.

In our next chapter, we'll get acquainted with an extremely lively friend, a friend that you can keep applying forces to, and a friend that can take any shape and size that you'd like—yes it's none other than our great friend Box2D!