Skills, tools and a shared knowledge base that let any AI coding agent mod almost any PC game you own.
The agent finds the game, works out the engine and the route, reads the real code, builds the mod, makes art, 3D and sound
with fal, tests it in the running game, cuts the video, and writes down what it learned for the next agent.
Coming next: the mod hub. Publish your mods, remix other people's, and make new ones.
Install
Pick your agent. Each gets the same skills (Agent Skills format), the fal MCP server, and the um CLI.
| Agent | Install |
|---|---|
| Claude Code | /plugin marketplace add rehan-remade/universal-modder/plugin install universal-modder@universal-modder |
| Codex | codex plugin marketplace add rehan-remade/universal-moddercodex plugin add universal-modder@universal-modder |
| Gemini CLI | gemini extensions install https://github.com/rehan-remade/universal-modder |
| VS Code / Copilot | Enable chat.plugins.enabled, run Chat: Install Plugin From Source, and enter this repo's URL |
| Cursor | Cursor Marketplace, or clone (Cursor reads AGENTS.md and .cursor/mcp.json) |
| OpenCode | Clone and run opencode inside it (opencode.json adds the skills and the fal MCP server) |
| Skills only
(any agent) | npx skills add https://github.com/rehan-remade/universal-modder |
| Anything else | git clone https://github.com/rehan-remade/universal-modder and start your agent inside it |
Inside a clone, each agent finds the skills where it looks for them: .agents/skills (Codex, Gemini CLI,
Copilot, Cursor, OpenCode) and .claude/skills (Claude Code) are copies of skills/. Instructions are in
AGENTS.md, which CLAUDE.md and GEMINI.md point to. MCP config is in .mcp.json, .codex/config.toml,
.cursor/mcp.json, .vscode/mcp.json and opencode.json (which also points OpenCode at skills/).
The um CLI. Plugin installs and clones put it on PATH. Anywhere else:
uv tool install git+https://github.com/rehan-remade/universal-modder # or: pipx install git+...um fal (for images without a key, um comfy uses a local ComfyUI server):
export FAL_KEY=...uv is recommended. Blender is needed for 3D → sprite renders.
Windows games are driven natively or from WSL.
Try it
Mod Terraria: add a homing missile launcher and a tactical nuke that craters the world. Make the sprites with fal.
Make a new civilization for Age of Empires II with a unique unit rendered from 3D.
Put real Minecraft inside GTA V story mode. Minecraft's camera should follow GTA's, and its TNT should blow up GTA cars.
Port the Warthog from my Halo install into Minecraft, with a gunner on the turret.
What engine is C:\Games\Foo, and has anyone modded it before?
The agent starts with the mod-any-game skill and runs the same loop every time:
- search the knowledge base;
- recon, then pick a route;
- set up a safe lab (saves backed up);
- read the actual code;
- build one working slice;
- generate assets;
- verify in the real game;
- record;
- package;
- write a field note for the next agent.
A knowledge base that AIs write for AIs
knowledge/ holds field notes: how specific games were actually modded, decompiled and
reverse-engineered. Each note gives:
- the exact versions that worked;
- the route, and why;
- what the engine really does;
- how it was verified;
- the gotchas (symptom → cause → fix).
um kb search "grand theft auto" # before you start: prior art (works outside the repo too)
um kb new --game "Hades II" --title "A new boon god" --from-scan hades --agent "Codex (gpt-6)"
um kb check knowledge/games/hades-ii/a-new-boon-god.md
um kb pr knowledge/games/hades-ii/a-new-boon-god.md --yes # after your human says OK: branch, push, PRknowledge/INDEX.md. Every game is welcome. Contribution rules, for humans and
AIs, are in CONTRIBUTING.md: no game files, no decompiled dumps, no cheating other
players, and an honest status and verification.
A few notes from the community:
- Portalcraft: real Minecraft inside Portal 2
- Halo 3 weapons, Covenant, vehicles and maps ported into Minecraft
- Bloons TD 6 inside Minecraft, with the game's rules as a headless sim
- A CS2-style conversion of Elden Ring offline, as a native Rust DLL
What's inside
Skills (skills/, Agent Skills format)
| Skill | What it does |
|---|---|
mod-any-game | The whole loop, hard safety rules, and 12 engine playbooks: Unity, Unreal, .NET/XNA (Terraria, Stardew, Celeste), Godot, Source 1/2, Bethesda, Minecraft, AoE2/Genie, RE Engine/FromSoft/GTA/Cyberpunk/BG3, native C++, indie engines (GameMaker, RPG Maker, Ren'Py, Paradox, Doom, HTML5, LÖVE, Java), retro decomps |
game-recon | Prior field notes, engine and version, managed or native, anti-cheat, loaders, save folders, community route → MODDING_PLAN.md |
reverse-engineering | ILSpy / Cpp2IL / Vineflower / Ghidra and IDA over MCP / Cheat Engine / Frida / RenderDoc; reverse-engineer a file format and prove it with a round trip |
fal-assets | Sprites with real transparency, consistent variants, pixel art, seamless textures, PBR maps, image-to-3D, auto-rigging, SFX, music, voice, cutscene video |
asset-pipeline | Art → engine-exact frames: cutout, nearest-neighbour fit, palettes, sheets, team-colour masks, 3D → 8/16-heading sprites |
game-automation | Launch, screenshot (GPU-safe), click/type safely, windowed mode, crash-reporter cleanup, in-game agent bridges |
showcase-video | Record the window with only the game's audio, pick moments, cut a styled video from an EDL |
mashup-mods | Game inside a game: content ports, passthrough mods (worked example: Minecraft × GTA V), decomps as libraries, reimplementations |
publish-mod | Lint, package per platform, credits, the post |
share-field-notes | Search the knowledge base, write your own note, open the PR |
The um CLI (Python). Every command has --help with examples.
| Command | What it does | |
|---|---|---|
 | um scan | Find Steam/Epic/Xbox installs; fingerprint engine and version, .NET vs native, anti-cheat, installed loaders, save folders, ranked routes |
 | um fal | sprite, image, edit, rmbg, pixelate, upscale, texture, pbr, model3d, rig, sfx, music, voice, video, run, search, schema, price. Plain REST, with a manifest of every generation |
 | um comfy | status, image (--sprite cuts it out), run (any workflow saved with Export (API)). Images from a local ComfyUI server, no API key |
 | um sprite | cutout, fit, pixelate, palette, sheet, slice, frames, team-mask, seamless, preview |
 | um render3d | GLB → sprite frames from the game's camera (aoe2, iso8, trueiso, topdown, side, turntable) with Blender |
 | um win | shot, record (gfxcapture + process-loopback audio), drive (input that only reaches the game), ps, kill, launch, reg |
 | um video | contact sheets, compile (EDL → titled, beat-cut video with music), mux, beats, first-frame |
 | um backup | Snapshot, diff and restore save folders |
 | um publish check | Blocks shipping game files, decompiled code and leaked keys |
 | um kb | The knowledge base: search, show, new, check, index, sync, pr |
Two no-build Windows tools ship inside the package (um/ps1/): WinDrive input and ProcLoopback game-only
audio, both PowerShell with embedded C#.
Built with it
- examples/terraria-tmodloader: Fal Arsenal for tModLoader.
- examples/aoe2-de-civ: San Franciscans for Age of Empires II DE.
.sld sprite writer.
- examples/minecraft-gta5-passthrough: real Minecraft inside
Each has a field note with every non-obvious lesson: knowledge/INDEX.md.
Rules it follows
- Any game you own: single-player, multiplayer, or servers you host. It refuses to inject into online
- It never ships game files or decompiled code. Mods ship as code, your own assets, patches or
- It backs up before touching saves, and kills processes by PID only.
- It asks before driving your mouse and keyboard, installing loaders into game folders, or publishing,
Full reasoning: skills/mod-any-game/references/safety.md.
Made a mod with it?
Put the badge on your mod's page:
made-with-light.svg on a light page.
Credits
- Built from real agent sessions modding Terraria, Age of Empires II and GTA V × Minecraft.
- Assets: fal (GPT Image 2, Nano Banana 2, FLUX, Trellis 2, ElevenLabs...).
- Standing on the shoulders of tModLoader, genieutils-py, AoE2ScenarioParser, ScriptHookV, ReShade, Fabric,
- The engine playbooks also draw on the September 2026 wave of AI-built mods, and on how their creators
MIT licensed. Brand type: Geist Pixel, Sometype Mono and Instrument Sans. Video titles: Space Grotesk and JetBrains Mono. All under the SIL OFL.
Star history
