It feels like generative AI is everywhere in game development—a Google survey estimated 87% of game developers are using it in some capacity—but generative AI is really everywhere in Codex Mortis, a Vampire Survivors-esque game the developer has called "the world's first fully playable game created 100% through AI" in a press release. Reminds me a bit of those labels on certain sodas that assure you they contain absolutely no real fruit juice.
The game's developer, under the username Crunchfest3, posted about the development process on the AI game dev subreddit. The dev claimed that they forewent the use of a game engine, and that everything was slapped together with AI tools in just three months (though it was slightly more complicated than just typing an idea for a game into a text field).
"It's pure TypeScript. I use PIXI.js for rendering, bitECS for the entity-component-system backend, and Electron to wrap it as a desktop app," Crunchfest3 wrote. "The whole thing was vibe-coded with Claude Code (mostly Opus 4.1 and 4.5)." The art, meanwhile, was generated by ChatGPT, and the game's animations "are a shader written by Claude Code."
The game is only available in demo form at the moment on its Steam page. It takes a deliberately provocative posture, with its AI-generated cinematic trailer showing a robed sorcerer vaporizing a demon labeled "AI antis."
The game itself certainly looks like AI made it, too: it's a bullet heaven in the vein of Vampire Survivors with a muddy, indistinct art style as the only element that visually distinguishes it from its inspirations. Still, it appears to be an honest-to-God videogame with many of its genre's trappings, which is interpretable as a milestone for the technology as a coding tool.
The game's claim to be a world's first is hard to verify. Hobby coder David Friedman's Doomscroll is a browser game that was generated using ChatGPT, and I'm sure there are plenty of other games out there with similar ambitions to use generative AI for all it's worth in the game development process. Perhaps Codex Mortis is unique in that it's releasing on Steam, potentially as a paid product, but still, I'm not sure "vibe-coded" is necessarily a distinction to be proud of.
