I'm curious, what is modding Sonic 1 SMS like? Are you using a disassembly, or a hex editor? Asking because I might get into Sonic ROM Hacking
There is a feature-complete editor out there for use called STH1ED I think is what its called? You do need some hex tweaks. Once I come back to this I will probably switch to the Sonic 2 8-bit engine, we'll see.