I learn a lot doing https://skilldrick.github.io/easy6502/ https://skilldrick.github.io/easy6502/ and hope there are other on that level for z80, x86 and arm.

I learn a lot doing https://skilldrick.github.io/easy6502/ https://skilldrick.github.io/easy6502/ and hope there are other on that level for z80, x86 and arm. May be 6502 is just simplifier. But dealing with basic memory, asm, machine code, cpu and flags are so intuitive when you got a javascript emulator using canvas.