And the simple front with the fractal complexity below it also make this more fun and educational: You can start off easy while still getting good results, and

And the simple front with the fractal complexity below it also make this more fun and educational: You can start off easy while still getting good results, and go arbitrarily deep in perfecting your emulator, choosing from an apparently still unexhausted variety of interesting problems to solve. Your links are a good example, I love reading about the complex implementation details in emulators of superficially simple hardware.