Codex Mortis, a new game inspired by Vampire Survivors, boldly claims to be a product of “100 percent AI-driven” design, encompassing everything from its code and assets to the music.

Developed by Grolaf, also known as Crunchfest, this project took just three months to complete and was crafted entirely through AI tools, utilizing Chat GPT for artwork and a shader developed by Claude Code for animations.

Rather than using a traditional game engine, the developer opted for a “pure TypeScript” approach, explaining that they leveraged PIXI.js for rendering, bitECS for the entity-component-system backend, and utilized Electron to package it as a desktop application. The entire development was styled using Claude Code, particularly versions 4.1 and 4.5.

“In Codex Mortis, Death is your weapon,” the description provocatively states. Players can combine five schools of dark magic, unleash powerful spell synergies, and summon undead armies in this necromantic bullet hell experience. Featuring infinite build possibilities, players can choose to go solo or team up in co-op mode while embracing the dark arts.

The game’s creator mentioned that they began with a prototype to test the concept’s feasibility, which evolved through iterative development.

“Achieving a consistent art style was challenging, but GPT was able to remember my preferred visual elements and maintain that style across various sessions,” the developer shared in response to feedback. “I relied solely on GPT for this, not the image API. I faced difficulties getting character animations to function as intended, so I settled for shader-based wobbling instead.”

“This marks my first attempt at building a project without a conventional engine. Integrating Steam with Electron was not as seamless as with Unity or Unreal. I initially tried Tauri, but it didn’t cooperate well with Steam.”

“An important lesson learned: this approach is significantly less mentally taxing compared to traditional app development; it feels akin to providing an exoskeleton to a construction worker,” they humorously remarked.

Though the game has not yet launched, its Steam discussion forums are active with mixed reactions, including threads titled “Lmao, this looks like ass,” “Garbage AI slop,” and “100% AI generated – don’t buy and don’t support this.” There is one thread questioning the backlash, simply asking, “Why is everyone upset about AI in game development?”

On the r/aigamedev forum, the comments were slightly more positive, although some responses have been removed, leaving their sentiment unclear.

Curious players can test the free demo on Steam, which currently holds a ‘Mixed’ rating. One reviewer commented, “The [free] demo is at least worth the price.”