Net Forge

Net Forge, the open-source multiplayer browser game engine built for AI coding agents: @netforge on npm, https://github.com/netnetdev/net-forge and https://forge.netnet.capital/docs. Not affiliated with other projects named NetForge.

Net Forge is an open-source (MIT) TypeScript engine for multiplayer browser games. One simulation (ECS, Rapier physics, a fixed tick and snapshots) runs in the browser and on an authoritative room server, a three.js renderer (WebGPU with a WebGL2 fallback) draws it, and ten finished multiplayer games ship as templates you can change. The game API is typed and declarative, and an MCP server lets your own coding agent build, validate, playtest and run a game.

Start in 30 seconds

npm create netforge@latest my-game -- --template survivor --yes
cd my-game
npm run play       # opens http://127.0.0.1:4663, more tabs are more players

The whole game is my-game/src/game.ts. Edit it, run npm test (it compiles the rules and plays them with bots), then npm run play again and open the link in a second tab to play together. Everything runs on your computer with play money: no wallet, no chain and no hosted servers.

Leave out --template and --yes to pick from the ten templates. Each new game carries AGENTS.md (with CLAUDE.md, Cursor and Copilot pointers) and the MCP entry for @netforge/mcp in .mcp.json, .cursor/mcp.json and .vscode/mcp.json, so a coding agent knows how to change, test and run it. packages/create-netforge lists every option.

What it does for you

• One simulation on both sides. @netforge/engine-sim runs the same deterministic ECS and Rapier world in the browser and on the room server, with input commands, delta snapshots and bit-exact restore.
• Finished games, not empty projects. Every template is a complete multiplayer game with rendering, input (keys, gamepad, touch), HUD, game feel, bots and a headless playtest.
• Declarative games. A game is declarations (game, prefab, weapon, upgrade, director, system, earn.rule and each genre's own), checked by schema validators with messages that say what to fix.
• Built for coding agents. @netforge/mcp gives an agent tools to pick a template, scaffold, search the docs, validate, playtest with bots and play locally. Every template ships AGENTS.md, CLAUDE.md, llms.txt and llms-full.txt.
• Playtests with numbers. engine.test.run plays the game with bots on the server simulation and reports kills, waves, deaths, softlocks, earn and milliseconds per tick.
• Free assets. A library of CC0 models, sprites and sounds in six art styles, addressed by id.

Templates

Template	Genre	Players	What it shows
survivor	Survivor-like co-op (EMBERWATCH)	1 to 4	2,000 enemies on one field, auto-firing weapons, level-ups, bosses
arena	Arena shooter (VOLTYARD)	up to 16	Twin-stick rounds, bots fill empty seats
tower-defense	Tower defense (COGSPIRE)	1 to 4	Shared board, twenty waves, tower upgrades
dungeon	Co-op dungeon crawl (CRYPTWICK)	1 to 4	Seeded rooms and corridors, permadeath runs
idle	Idle (BRINEWORKS)	up to 8	Plants, products and a shared contract per shift
platformer	Platformer race (SKYLEDGE)	up to 8	Jump, dash, moving platforms, coins
cards	Card battler (INKWRIT)	2	One against one, drafts between duels, AI opponents
collector	Monster collector (MOSSBOUND)	up to 8	Turn-based battles, a team of three, a shared final boss
racer	Kart racer (TORQUEBAY)	up to 8	Drift turbo, boost pads, bots fill the grid
party	Party co-op (ROMPHOUSE)	2 to 8	Five minigame rounds a show

Each template's README in packages/template-* has its own run steps.

Use with your coding agent

claude mcp add netforge -- npx -y @netforge/mcp     # Claude Code
npx netforge setup agent                            # AGENTS.md, CLAUDE.md, Cursor rules, .mcp.json in this project
npx skills add netnetdev/net-forge                  # Agent Skills: create, add content, playtest, play locally

Cursor and VS Code read the MCP entry that npx netforge setup agent writes (.cursor/mcp.json, .vscode/mcp.json). The tools are netforge_list_templates, netforge_create_game, netforge_search_docs, netforge_explain_api, netforge_validate_game, netforge_run_playtest and netforge_play_locally; see packages/mcp.

Packages

Package	What it is
@netforge/asset-library-files	Built CC0 game asset files for Net Forge (optimized models, sprites, textures and sounds) that kit play serves to a game running locally.
@netforge/asset-library	CC0 game asset library for Net Forge: a manifest of models, sprites and sounds addressed by library id, shared rigs, the look composer and a three.js loader.
create-netforge	Start a game with Net Forge, the open-source multiplayer browser game engine built for AI coding agents: npm create netforge@latest my-game. Ten templates, play money, AGENTS.md and MCP config included.
@netforge/engine-sim	Deterministic game simulation shared by browser client and server for Net Forge: ECS, Rapier physics, a fixed tick, input commands and delta snapshots.
@netforge/engine	Net Forge game engine client: a typed declarative game API and a three.js WebGPU/WebGL2 renderer for multiplayer browser games.
@netforge/kit-play	Make, test and run Net Forge games on your own computer with play money: start a game from a template, run playtest bots, and play it in the browser with a local room host, with no wallet, chain or servers.
@netforge/mcp	MCP server for Net Forge: lets AI coding agents list templates, scaffold a game, search the engine docs, validate a game module, run headless bot playtests and play the game locally. No chain, no keys.
netforge	Net Forge command line for coding agents: npx netforge setup agent writes AGENTS.md, CLAUDE.md, Cursor rules and MCP configs into a game project, and ships Agent Skills for building Net Forge games.
@netforge/tabletop	Shared client kit for Net Forge board-style game templates (tower defense, idle, card battler, monster collector): room connection, input clock, 3D stage, store and HUD.
@netforge/template-arena	Arena shooter game template for Net Forge: up to 16 players, lag-compensated beams, loadouts, rounds and seat-filling bots (VOLTYARD).
@netforge/template-cards	Card battler game template for Net Forge: one against one or against the AI, a gauntlet of duels with drafts, server-side shuffle and hidden hands (INKWRIT).
@netforge/template-collector	Monster collector game template for Net Forge: a shared marsh where players catch creatures and battle turn by turn with a team of three (MOSSBOUND).
@netforge/template-dungeon	Co-op dungeon crawler game template for Net Forge: 4 players, procedural rooms, loot and permadeath runs (CRYPTWICK).
@netforge/template-idle	Shared idle game template for Net Forge: up to 8 players pump, boil and cut salt to fill a contract together (BRINEWORKS).
@netforge/template-party	Party game template for Net Forge: 2 to 8 friends in one playroom, five quick minigame rounds a show (ROMPHOUSE).
@netforge/template-platformer	Multiplayer platformer game template for Net Forge: races to the flag with coyote time, jump buffering, dashes, springs and moving platforms (SKYLEDGE).
@netforge/template-racer	Kart racer game template for Net Forge: harbour circuits with drift mini-turbos, boost pads, coins and laps at 60 Hz, with seat-filling bots (TORQUEBAY).
@netforge/template-survivor	Survivor-like co-op game template for Net Forge: 4 players, 2,000 enemies, authoritative multiplayer (EMBERWATCH).
@netforge/template-tower	Co-op tower defense game template for Net Forge: up to 4 players, waves, building and upgrades, shared lives (COGSPIRE).
@netforge/kit	Optional on-chain add-on for browser games: a game token, a store, payments and a mandatory earn mechanism, with a runtime library, a CLI and an MCP server (Net Forge Cabinet Kit).

@netforge/kit is the optional on-chain add-on (a game token, a store and payments). Nothing else depends on it, and it is published separately.

Work on the packages

Needs Node 22 and pnpm 10.

pnpm install --frozen-lockfile
pnpm build
pnpm typecheck
pnpm test

What is not here

The hosted room server, the referee that decides real payouts, the studio and its generator, the asset pipeline that builds the library, and the on-chain contracts are not part of this repository. Games built here run with play money only.

Links

• Docs: https://forge.netnet.capital/docs (every page also as markdown; full corpus at https://forge.netnet.capital/llms-full.txt)
• Contributing: CONTRIBUTING.md. Issues are welcome; pull requests are applied upstream and come back with the next export.
• Security: SECURITY.md
• Releases: packages are published to npm by .github/workflows/publish.yml when a tag named engine-v* is pushed, dependencies first, with npm provenance.

License

Every package is MIT licensed (LICENSE). The library assets are CC0 1.0 (see NOTICE).