In December, I set out to write an NES #emulator from scratch, working on it an hour a day every day, recording every minute. (It's not quite the same as #AdventOfCode but it's close.) I've built the CPU, PPU, and a handful of mappers. I added MMC3 without IRQ yesterday, and the end of the session's time lapse shows the first area of Full Quiet.
I don't seek pedantic accuracy needed to console-verify a tool-assisted speedrun or troubleshoot an ill-behaved game engine, nor broad support for mappers I've never used in a game. I do plan to investigate extending the NES platform to accommodate 16:9 TVs, like the PC Engine does.