Benchmarking frontier models by porting Prince of Persia from 6502 assembly to C#

Analyzing Frontier Model Progress with My Favourite Game: Prince of Persia

The author fed the original 6502 assembly source of Prince of Persia (Apple II, 1989) to frontier models and asked them to port it to C#. Claude Opus 4.6 produced a tile-grid engine that didn't play like the real game. OpenAI Codex fixed rendering details but left the broken architecture. Claude Opus 5, given DOSBox screenshots, diagnosed the architecture problem, rebuilt the engine, and read real animation frames and all 15 levels directly from the DOS game files. Claude Opus 5.5 ported the community-reverse-engineered room-drawing routine and reduced pixel differences on level 1 from 8,429 to 2. The post does not disclose Opus 5.5's exact release date or per-call cost.

Why it matters: A first-person experiment that stress-tests three Claude generations against the same 6502 assembly source, with failure modes specific enough to learn from. Not a product launch or industry event, so it stays in the good-quality band, but the signal-to-noise ratio is excellen...