New Vampire Survivors-a-like Codex Mortis is perhaps one of the first games to proudly declare that everything, from its assets and code to the music, is “100 percent AI-driven”.

Developer Grolaf, aka Crunchfest, admits the game – which has taken three months to make – is created entirely with AI, with artwork created in Chat GPT, and animations created using “a shader written by Claude Code”.

No game engine was used – “it’s pure TypeScript”, apparently – with the developer explaining “I use PIXI.js for rendering, bitECS for the entity-component-system backend, and Electron to wrap it as a desktop app. The whole thing was vibe-coded with Claude Code (mostly Opus 4.1 and 4.5).” You can see it in action in the video below.

“In Codex Mortis, Death is your weapon,” the blurb teases (thanks, PC Gamer). “Mix five schools of dark magic, unleash devastating spell synergies, and raise undead armies in this necromantic bullet hell. Infinite builds, solo or co-op – embrace the forbidden and dominate. 100% AI-driven development.”

The developer said they started with a prototype “just to see if this was even feasible”, and iterated from there.

“Maintaining a consistent art style was tricky, but GPT managed to remember what visual style I liked and kept it consistent across different sessions,” he told one commenter. “I just used regular GPT, not the image API. I also couldn’t get character animations to work properly, so I went with shader-based wobbling instead.

“First time building something without an engine. Integrating Steam with Electron wasn’t as smooth as it is with Unity or Unreal. I tried Tauri first but it doesn’t play nice with Steam at all.

“And the most important takeaway: compared to traditional app development, this is way less mentally draining – kind of like giving an exoskeleton to a construction worker lol.”

While the game is yet to release, its Steam discussion forums are full with threads entitled “Lmao, this looks like ass”, “Garbage AI slop”, “Dangerous slippery slope”, and “100% AI generated – don’t buy and don’t support this”.

There’s only one thread that I could find that was ambivalent about its development, which simply asks: “Why everyone is butthurt about IA [sic] in game development?”

Commenters over on r/aigamedev were a little less hostile, although several responses have been deleted, so make of that what you will.

Those intrigued can try out the free Steam demo, although that’s currently sitting on a ‘Mixed’ rating, with one reviewer writing “The [free] demo is, at least, worth the price”.