Imagesource: https://github.com/iaddis/

For the following you need time. A lot of time. And you also really need to be very attached to the few-thousand-transistor-cpu-architectures-of-80s CPUs to really dig into this topic.

The short version: Icer Addis aka Sardu introduced MetalNES, a transistor-level NES simulator, a few days ago.

Despite current gigahertz bolides, the thing is so snore-slow that you don't even have to think about wanting to play a game of any sorts. The whole project has rather the purpose to rebuild the overall architecture of the NES (however without MMU) on transistor level and has real educational value.

If you have the time I just mentioned (congratulations! 🙇‍♂️) and if you are attracted to the 6502 and the NES architecture, this project is pure gold.

Unfortunately it is currently only available on the Mac.