Congrats on getting this far. If this book were a game, we'd probably have earned an achievement for this chapter alone. As we saw, working with a low-level API such as Metal can be a bit daunting. We first reviewed what it means when developers and engineers mention lower and upper level frameworks and code. On the CPU side, we saw that the lowest level is the machine's code with Swift and Objective-C in the middle, and above C/C++ and Assembly code. Next, we spoke about the GPU side and where the visual graphics APIs we've gone over in the past chapters stand in the hierarchy. We then got an understanding of the history of lower-level graphics APIs such as OpenGL ES, how the graphic pipeline generally works under the hood, and how to make basic shaders. Finally, we reviewed why Metal is faster during the render cycle than OpenGL, the general structure behind Metal, and some of the code/objects used to manually set up the render loop. This chapter merely scratched the surface on this topic, so if you are up to the challenge, it's highly recommended to continue reading documentation on how Metal can make your games stand out from the rest.

At this point, you should now have all that it takes to make a game on the iOS platform. The last essential lesson for iOS game development is learning how to test, publish, and update your published game in the app store. In the next chapter, let's learn how to get that game on the Apple app store.