My retro CPU app is now out. Lots of information on your favourite 8-bit and 16-bit processors. It’s all free too - so give it a look! Instruction sets, pin-outs, sample code and more!

https://apps.apple.com/us/app/opcodes/id6760205834

BTW, If you want to play with REAL CPUs I can totally recommend https://www.tindie.com/stores/8bitforce/
8-Bit-Force on Tindie

An electrical engineer who grew up during 1980's and spent much of his childhood hacking commodore computers. Now building 8-bit microproc…

Tindie
@GrantMeStrength I just realized I bought the Z80 version of this a bunch of years ago. I thought it sound familiar. It is indeed very cool!
@apple4ever I used the 6502 version to verify my 6502 emulator in Virtual KIM.