Your agents play the game before they tell you it works.
A lightweight engine and world bible for teams that build with agents. Agents do the plumbing, the testing and the first drafts. You keep the craft.
Ten agents. Ten engines. Every result proven.
What it is for, and how early it is
Games it is for
Stylised 3D adventure, open world, survival and crafting games, in the vein of Raft and The Last Caretaker. Painted 2D adventures work too. No art style is forced.
What it handles well today is the heart of those games at a smaller size: hand-built stylised spaces, interiors and vehicles (a raft deck, a ship, a station, a building, a painted room), with characters walking, carrying, sitting and building from parts. The bigger target is where it is heading.
gejm.dev does not compete with Unreal on photoreal, big-budget games.
Not yet
- Co-op The simulation is split between server and client already, but there is no network.
- Open-world size No terrain, water, streaming or level of detail yet.
- Player saves Saving the player's game across versions of the game.
- Sky and creatures Time of day, weather, and navmesh for creatures.
- Other platforms Windows only for now.
How early
- Early access Not a beta of a finished product. The engine grows with the games being built on it.
- Breaking changes happen File formats, script APIs and tools change without a migration path while the engine finds its shape.
- No ship date soon Not for teams shipping in the next months.
See it run
One request fans out into ten sessions. Each one gets its own headless engine, steps the world, plays the game and passes its test. The drafts come back to a person for review.
- write TypeScript, with a definite typecheck answer for what is on disk
- set up the situation in one call: spawn, set a component, reset from a snapshot
- step the world tick by tick, drive the player, walk it to a point
- query the world back: what happened, where, and why
- prove it with a test that names the rule it proves
The problem, in developers' own words
“Appears valid but the game is actually unplayable.”
“Has no way to see what it's producing.”
“Each session starts cold.”
How it works
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Canon
Canon in the bible
Characters, places, props and styles live in gejm.dev Bible. Agents draft; a person accepts every change.
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Plan
A feature planned
Written in someone's own words, turned into a spec with one provable rule per line, citing the bible.
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Build
Sessions in parallel
Each slice gets its own agent and its own headless engine, and proves its own work.
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Draft
Drafts to the artist
Models at gameplay scale with collision and sockets working, finished by the artist in Blender.
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Play
Play and prove
A playtest note carries its replay, so the agent reproduces what the tester saw and proves the fix.
Who it is for
For developers
Play and prove, parallel sessions, deterministic replay, walk a system line by line, everything as text, any agent.
For artists
Drafts at gameplay scale, finished in Blender, checked on every export. Drafts are where you start, not what ships.
For writers
One canon, agents propose and people approve, contradiction checks, concept art that follows the style guide.
Our stance on AI
gejm.dev does not replace artists or game developers. The agent does the plumbing, the checking and the drafts. People keep the craft and the final say.
Works with
- Claude Code
- Codex
- Cursor
- Any MCP client
- Blender
- KiwiPow IDE and Server
gejm.dev Bible also works with Unity, Unreal and Godot. All integrations
Built in the open
The engine is open source. Its code is on GitHub; its specs, roadmap and plans are public on KiwiPow Server, where every behaviour is planned and proven by a named test.
How it compares
| Plays its own work | Parallel sessions | Files as text | A canon | |
|---|---|---|---|---|
| Editor engines with an MCP plugin | Mostly edits | One editor per project | Scenes and Blueprints are hard to diff | No |
| Agent add-ons | Some send input and take screenshots | Bound to the editor | As the engine below them | No |
| Prompt-to-game tools | No | No | Varies | No |
| gejm.dev | Every session steps, plays and tests | A headless engine per session | Scripts, generators, scenes and reports | gejm.dev Bible |
Compiled October 2026. The full comparison
Early access
Free during early access. For small teams and solo developers who already build with coding agents, are making one of the game types above for Windows, and want to shape the engine.
What we ask: playtest notes, honest reports, and permission to show your game when it is ready.
Join the early access