Code is organized by chapter, denoted by the listing name. As the book progresses, we use more and more of the gameobjects library.

Games can be modified by copying their source code. The copy command will create a Python file in your local directory which you can edit. For example, to copy and play the "snake" game run: $ python3 ...

Since there is no official source code available for Super Mario Bros, ... he wrapped the game’s ROM data into py65emu, a Python library emulating the 6502, the CPU that drives the NES.