Retro Game Mechanics Explained is a YouTube channel that goes over some of the most highly technical explanations of retro games and systems i've ever seen. In the video i've linked above he talks about the Game Genie which I never really thought about but the explanation of how it works makes sense and it's such an elegant solution to the problem I tip my hat to the developers of it. Bit of a warning though, it's highly technical and discusses some pretty low level computer concepts such as registers and op codes.

Enjoy!