some weeks ago I made a Gameboy emulator from zero in rust and then exported it to wasm
https://holy-lake-f6df.sdreyesg.workers.dev/
took me 3 hours with Opus. Opus knew the whole ISA, clock, bus quirks, etc. from their training without any external docs
Yes, this project was made in around 15 hours of Codex.
Likely because all of the external docs were already in its training set.