Monster collector multiplayer browser game template for Net Forge, the open-source multiplayer browser game engine built for AI coding agents.

This is a template for a monster collector that runs in the browser: MOSSBOUND, a complete multiplayer game you can start in one command and change in one file. A multiplayer monster collector: pick a starter, walk a shared marsh, meet wild creatures in tall grass, battle turn by turn with a team of three and catch the ones worth keeping.

What you get

• Up to 8 players in one shared marsh.
• Three starters, wild creatures in tall grass, turn-based battles with a team of three, and catching.
• A shared boss, the warden, that every player wears down and that has to fall before dusk.
• An authoritative room at 30 Hz; battles are integer state on the server.
• Authoritative multiplayer. A room host owns the game state; every browser tab is a player. Locally, npm run play runs that host on your computer.
• Shared client/server simulation. The same ECS and Rapier physics code steps the world on the server and predicts your own player in the browser, with delta snapshots.
• three.js renderer with WebGPU, and a WebGL2 fallback.
• Bots and a headless playtest. npm run test plays the game with bots and reports what happened.
• TypeScript, MIT licensed. The library models, sprites and sounds the game uses are CC0.
• Ready for coding agents. AGENTS.md, CLAUDE.md, Cursor rules, Copilot instructions and the Net Forge MCP server in .mcp.json, .cursor/mcp.json and .vscode/mcp.json.

Measured with npm run test (2 bots, 1 minute of game time, Node 22, Apple M2 Pro):

Playtest report	Value
Ticks simulated at 30 Hz	1,800
Highest creature level	4
Earn rules fired (play money)	2
Server cost per tick (mean)	under 0.005 ms
Softlock	none

Every number above is play money and a local run. Longer runs: npm run test -- --minutes 4 --bots 4.

Start in one command

npx create-netforge my-game --template collector --yes
cd my-game
npm run play

Or press Use this template on GitHub, clone your new repository, and run:

npm install && npm run play

npm run play builds the game, starts a local room and opens http://127.0.0.1:4663. Open the same link in another tab for a second player. Walk with WASD, the arrows or the left thumb. Open the link in a second tab and you meet the other keeper in the marsh.

You need Node.js 20 or newer. Use npm run play -- --no-open to print the link instead, --port 4700 if the port is taken, and --host 0.0.0.0 to let phones on your network join. Local play uses play money: no wallet, no chain and no hosted servers.

Change the rules

The whole game is src/game.ts: declarations against the typed API in @netforge/engine (the only import it may make). The template package @netforge/template-collector provides the renderer, netcode, physics, controls, HUD and bots.

npm run test        # compile src/game.ts and play it with bots; fails on a broken rule or a softlock
npm run typecheck   # the TypeScript check of src/game.ts
npm run play        # play the change (stop and start it again after each edit)

The template guide walks through the usual changes:

• Add a creature and a move
• Lay out the marsh
• Add an earn rule
• Check it with bots

llms.txt holds the rules the build enforces and recipes for common changes. Or ask your coding agent in plain words; AGENTS.md tells it where the rules live and how to test them.

Links

• Template guide: https://forge.netnet.capital/docs/templates/monster-collector
• Net Forge engine: https://github.com/netnetdev/net-forge
• Docs: https://forge.netnet.capital/docs
• npm: create-netforge, @netforge/template-collector, @netforge/engine

Pinned to Net Forge 0.2.0. Not affiliated with other projects named NetForge. Local play runs the game's own code on your computer with your permissions; play only games whose code you trust.

License

MIT (LICENSE). The library assets are CC0 1.0.