I set a hard 48-hour constraint to see how far I could get building a web Game Boy Advance emulator with Codex.

I started without deeply knowing the hardware spec. I used one seed prompt, then let Codex drive task decomposition, sequencing, and prioritization.

I ran 4 Codex coding agents in parallel on core emulator work, plus 1 Codex agent focused on testing and UI features. I used a continuous review and merge loop to keep all streams aligned.

Current result: I can render gameplay in the browser, and the game responds to action buttons. Runtime performance is still slow at around 11 FPS on average.

My current view is that performance can likely improve by running the agents longer and adding a dedicated performance-focused Codex agent to target hot paths.

If there is interest, I can share the Codex worker template, task format, and workflow.

Project repo: https://github.com/s0s0s0/Browser_GBA_Emulator