2d platformer game built with Codex (zero code)
Hi HN! On Sunday I spent a couple of hours building a short 2d platformer ("Prince of Persia" style). What's interesting is how I built it. I went for a zero-code approach, and built the whole thing using OpenAI Codex CLI and agent skills (with the progressive disclosure paradigm). You can play the game here: https://acatovic.github.io/gothicvania-codex-demo/ You can see the full code, agent skills and a complete writeup here: https://github.com/acatovic/gothicvania-codex-demo Some takeaways: * This was one of the most enjoyable experiences ever! *…
In plain words
A 2D platformer game in the style of Prince of Persia, created without writing code by using OpenAI Codex CLI and agent skills. The developer built the entire game in a couple of hours using a zero-code approach with progressive disclosure paradigm and automated implement-evaluate loops. Players can try the game online, and the full source code and documentation are available on GitHub for those interested in how it was constructed.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Hi HN! On Sunday I spent a couple of hours building a short 2d platformer ("Prince of Persia" style). What's interesting is how I built it. I went for a zero-code approach, and built the whole thing using OpenAI Codex CLI and agent skills (with the progressive disclosure paradigm). You can play the game here: https://acatovic.github.io/gothicvania-codex-demo/ You can see the full code, agent skills and a complete writeup here: https://github.com/acatovic/gothicvania-codex-demo Some takeaways: * This was one of the most enjoyable experiences ever! * Applying harness engineering with progressive disclosure is incredibly powerful - I treated my SKILL.md as simply a ToC (a "skills map") and took it from there * Implement -> Evaluate loops are key - I used Playwright and an evaluation checklist and the agent built and corrected automagically * I used PROGRESS.md as a memory/log mechanism for the agent, and a way to minimize context noise * The game dev agent was steered by the DESIGN-DOCUMENT.md, stipulating game objectives, layout and mechanics * I used progressive prompting - I built up the game piece wise - starting with basic player mechanics, then adding tiles, NPCs, interactions, sounds, menus - one prompt at a time Zero code written by me. Never even looked at the game engine (Phaser) API - just gave the skills a link to the documentation. The future is here! Credits to ansimuz (gothicvania assets) and Pascal Belisle (music). *NOTE:* The assets were *NOT* created by AI. Backgrounds and probably tiles you could generate with AI, but sprites are not quite there yet (I tried a number of different models). Something to explore fully in the future. Enjoy and let me know what you think!
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