Got through first 5 minutes and I already see that myself and the author have very different opinions on what constitutes "good code": 1) having data structure

Got through first 5 minutes and I already see that myself and the author have very different opinions on what constitutes "good code": 1) having data structure and its methods isolated in a module is not a bad thing. Modules provide an obvious boundary between pieces of code, so when calling some code from another module you know that you should care only about inputs and outputs and not about the particular implementation of the transformation. But when you have the same pieces of code mashed together in one module – that boundary is blurred, now compiler does not tell you that they don't interact via some shared state not named explicitly. 2) defining an interface to do a type switch. Really? Even if that interface is not exported, this still leads to more fragile code. When you rely on interface compiler will yell at you if you miss a method. But when you add a new type and forget to update one of those type switches – it will blow up in your face at run time. This is less relevant for NES emulator, since it was designed long ago and unlikely to get new entities that need to be accounted for, but doing this for no good reason can establish a habit that will bite you later in other projects.