Show HN: 2d platformer game built with Codex (zero code) https://ift.tt/jJpkIgN

Show HN: 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://ift.tt/trXI2TW 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! February 16, 2026 at 03:34AM