How to use Codex to build a browser GBA emulator
The emulator rendered gameplay in the browser and responded to action buttons, but average runtime performance remained slow at around 11 FPS.
news.ycombinator.com
Prompt to try
Editorial adaptation, not the source author’s exact prompt. Replace bracketed inputs and review tool permissions first.
Build a browser-based [console] emulator in [time limit]. Decompose and prioritize the work, assign [number] agents to core emulation and one to testing and UI, and use continuous review and merges to align changes. Demonstrate gameplay and button responses, then report measured runtime performance and remaining limitations.
Reach people exploring AI agents
See placements →What happened
The emulator rendered gameplay in the browser and responded to action buttons, but average runtime performance remained slow at around 11 FPS.
Reported by chakmanli on Hacker NewsHow the agent did it
- Set a hard 48-hour development constraint.
- Use a seed prompt to delegate decomposition and prioritization.
- Run four core coding agents and one testing and UI agent.
Where a person stepped in
The author used a continuous review and merge loop to align work and reported observed gameplay, input behavior and runtime limitations.
A person approved each step before the agent continued.
A developer set a 48-hour limit for building a web Game Boy Advance emulator with Codex. They began without deep knowledge of the hardware specification and used one seed prompt to let the agent drive task decomposition, sequencing, and prioritization. The seed prompt itself is not included in the supplied post.
The author ran four Codex coding agents in parallel on core emulator work and a fifth focused on testing and interface features. A continuous review and merge loop kept the separate streams aligned. This combination of delegated planning, parallel implementation, and repeated integration is the reported workflow; the source does not give individual worker assignments or the underlying emulator design.
At the time of the post, the emulator rendered gameplay in a browser and responded to action buttons. Runtime performance remained slow, averaging around 11 FPS. The author suggested that longer agent runs and a dedicated performance agent might improve hot paths, but did not report having completed that additional work. A project repository was supplied with the post. Who it's for: developers exploring an emulator prototype who can coordinate concurrent changes and accept a working interactive result with substantial performance limitations.
Prompt
Suggested prompt (written by Agents In Use, not the author's)
Source: Hacker News · chakmanli
Frequently asked questions
How were the five agents assigned?
Four Codex coding agents worked in parallel on core emulator tasks. One additional Codex agent focused on testing and UI features, with a continuous review and merge loop.
What worked at the time of the post?
Gameplay rendered in the browser and responded to action buttons. The author reported slow runtime performance at around 11 FPS on average; further performance work was only proposed.
More details
Remaining steps
- Continuously review and merge the parallel work.
- Run browser gameplay and assess input response and performance.
About this account
Codex drove task breakdown and prioritization, with five agents handling core emulator work, testing and UI features in parallel.
Platform: Hacker News. Attribution: https://news.ycombinator.com/item?id=47147633. Prompt: Suggested (written by Agents In Use, not the author's). Sourced by the Agents In Use pipeline.
Credit: chakmanli on Hacker News
Source published 25 Feb 2026
Source checked 14 Oct 2026
Tools and topics
Codex · Browser
GBA emulator · Parallel agents · Browser games
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.