Skills, tools and the fal MCP that let Claude Code mod almost any PC game you own.
It finds the game, works out the engine and the modding route, reads the real code, builds the mod,
generates art, 3D and sound with fal, tests it in the running game, and cuts the showcase video.

A tactical nuke in Terraria and robotaxis in Age of Empires II, both built with universal-modder

Install

As a Claude Code plugin (recommended):

/plugin marketplace add rehan-remade/universal-modder
/plugin install universal-modder@universal-modder

Or clone it and run Claude inside it (works with Codex/Cursor via AGENTS.md too):

git clone https://github.com/rehan-remade/universal-modder && cd universal-modder && claude

Then give it a fal API key for assets. It powers both the bundled fal MCP
server and the um fal CLI:

export FAL_KEY=...

You also need Python 3.10+ and ffmpeg. uv is recommended; the CLI sets up its own env with it. 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.

I own Skyrim SE. What would it take to put a Minecraft-style block-building mode in it?

What engine is C:\Games\Foo, and how do people mod it?

Claude starts with the mod-any-game skill and runs the same loop every time: recon, 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, then package.

What's inside

Skills (skills/)

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`	Which 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, 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, decomps as libraries, reimplementations
`publish-mod`	Lint, package per platform, credits, the post

The um CLI (bin/um, Python). Every command has --help with examples.


`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 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

Also bundled: the fal MCP server (.mcp.json), a SessionStart hook that puts um on PATH, and two
no-build Windows tools in tools/win/: WinDrive input and ProcLoopback game-only audio, both PowerShell with
embedded C#.

3D route: fal concept to 3D to 16 AoE2 headings. 2D route: fal art to cutout to a 64x26 Terraria sprite in game.

Built with it

examples/terraria-tmodloader: Fal Arsenal for tModLoader. A homing
missile launcher, a tactical nuke (crater + mushroom cloud), a chain-lightning rifle, a black-hole gun, an
orbital strike, three new enemies and a two-phase Drone Mothership boss. Every sprite came from fal.
examples/aoe2-de-civ: San Franciscans for Age of Empires II DE.
- A new civilization with a Robotaxi unique unit and Delivery Drones, rendered from fal image-to-3D models
  at AoE2's camera angle.
- A Transamerica Pyramid wonder.
- A reverse-engineered .sld sprite writer.

Both started as one-line prompts. The non-obvious lessons from each are written into the skills
(skills/mod-any-game/references/case-studies.md).

Rules it follows

Single-player and offline, on games you own. It refuses to inject into online games with anti-cheat,
write multiplayer cheats, or bypass anti-cheat, DRM or ownership checks.
It never ships game files or decompiled code. Mods ship as code, your own assets, patches or
converters.
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.

Credits

Built from real sessions of Claude Code modding Terraria and Age of Empires II.
Assets: fal (GPT Image 2, Nano Banana 2, FLUX, Trellis 2, ElevenLabs...).
Standing on the shoulders of tModLoader, genieutils-py, AoE2ScenarioParser, BepInEx, Harmony, UE4SS,
REFramework, SKSE, Fabric, ILSpy, Ghidra and every modding community that documented its game.
The engine playbooks also draw on the September 2026 wave of AI-built mods, and on how their creators
explained them in public.

MIT licensed. Fonts: Space Grotesk and JetBrains Mono (SIL OFL).