Either way, it's a really cool project! A working processor emulator, even a slow one, kind of makes you realize how deceptively simple lots of old CPUs are.

More like the original CPU/microprocessor. The man behind the Z80 was also the main contributor to Intel's 8080 as well as the 4004, which is arguably the foundation of a general purpose computer (calculator + memory) on an integrated circuit (microprocessor). I wouldn't say so much simple as it is ingenious.