I’ve spent a few months building this. It’s basically a visual env for the Intel 4004 because I wanted to see what's actually happening in the buses and registers without 'black boxes'.
It has a transpiler called QuadBasic to go from high-level syntaxs to native MCS-4 machine code. Just a personal project from a senior dev to tribute the 1971 pioneers. Happy to answer any tech questions if you find it interesting.