I think if you're new to emulation it's generally a good idea to start with something even simpler - the chip-8 system http://www.emulator101.com/introduction-

I think if you're new to emulation it's generally a good idea to start with something even simpler - the chip-8 system http://www.emulator101.com/introduction-to-chip-8.html http://www.emulator101.com/introduction-to-chip-8.html An average programmer can probably get an emulator for that running in a weekend, and there are lots of guides and documetnation out there for the opcodes and similar. NES / Gameboy / GameGear / similar are probably well-documented, but they will be harder at least because the processors have more opcodes you have to care about.