ChompChomp.io: a multiplayer snake .io game with server-authoritative anti-cheat

▶ Play ChompChomp.io now: free, in the browser, no download. Send the link to a friend and you're in the same arena.

ChompChomp.io is a slither-style browser game where snakes have guns. Eat glowing orbs to grow, grab power-ups and weapons, shoot rivals' bodies to slice them in half, and chomp anyone who crosses your path. It runs online with friends, with player accounts, saved stats, global leaderboards, and bots that fill the world and step aside as real players join.

It was built with Claude Code and the Multiplayer Agent plugin, starting from a single-player canvas game and turning it into a hosted multiplayer game. There's no game server to write, run or deploy. This repo is the full source, and it's part of the content package for the video made while building it.

ChompChomp.io gameplay: a snake moving through glowing orbs, with the live leaderboard and minimap

Features

Real-time multiplayer: everyone who opens the link plays in the same arena, synced 20 times a second.
Server-authoritative anti-cheat: the server decides movement, dots, power-ups, bullets, damage and scores. The browser only sends steering, boost and fire. You can't teleport, spawn power-ups, or fake a score.
Player login: you start as a guest instantly. Sign up to keep your progress and put your name on the leaderboards, and log in on any device.
Saved player data: games played, best score, longest snake, total kills, dots eaten and time played, all written by the server.
Global leaderboards: best score, total kills and longest snake, plus a live in-match leaderboard.
Bots that make room: 24 bots keep an empty world lively. Three retire for every player who joins, out of sight.
7 weapons and 17 power-ups: blaster, shotgun, twin guns, SMG, railgun, rocket launcher, homing seeker; shields, ghost mode, frenzy, vampire, nanobots and more.
Smooth netcode: client-side prediction for your own snake and interpolation for everyone else, so steering feels instant.
Desktop and mobile: mouse, keyboard or touch, with on-screen fire and boost buttons.

How to play

Action	Desktop	Mobile
Steer	Mouse	Drag
Shoot	Left click or `F`	FIRE button
Boost (costs length)	Right click, `Space` or `W`	BOOST button or two fingers

Body shots slice snakes; headshots drain health. Shooting is free under length 100, and smaller snakes fire faster. Running your head into another snake's body ends your run, and the world's red edge is deadly.

How the anti-cheat works

Most browser .io clones trust the client: the browser says where its snake is and what it ate. ChompChomp.io doesn't. The whole world is simulated on the server by authoritative room logic running on Multiplayer Agent:

 browser                                   Multiplayer Agent room "arena" (server)
 ───────                                   ───────────────────────────────────────
 mouse / keys ──► input {angle, boost, fire} ──► onInput: queue it, one per tick
                                                 onTick: move snakes, eat orbs, fire bullets,
                                                         collide, kill, spawn/retire bots
 draws snakes ◄── room state (snake heads, mass, power-ups) ◄─┘
 draws orbs   ◄── events (orb added/eaten, bullet fired/hit, effects)
 stats screen ◄── saveData / submitScore (only the server writes these)

Clients can't write room state. If a modified client sends fake "I ate this" or "I picked that up" messages, or sets its own position or mass, the server ignores it.
Inputs are validated: a steering angle, two booleans, nothing else. Speed and turning come from the server's rules, so a snake can't teleport.
Saves and leaderboard scores are written by the server from results it computed itself, so they can't be forged from the browser.
Your own snake is predicted locally from your inputs and corrected against the server every tick, so it still feels instant.

Run your own copy

You need Claude Code with the Multiplayer Agent plugin:

/plugin marketplace add multiplayeragent/multiplayer-agent
/plugin install multiplayer-agent@multiplayer-agent

Then ask Claude Code to "host this game on my own Multiplayer Agent game" in a clone of this repo. Claude will:

Create a game with create_game and put its publishable key (pk_…) in NET.key at the top of game.js. The key in this repo points at the live ChompChomp.io game, so without this step your copy joins that arena.
Build the server bundle with node build.js (Node 18+, no dependencies). This writes dist/server.js.
Deploy it with deploy_room_logic to the room arena, at tick rate 20. Server logic needs a Multiplayer Agent account; Claude opens the sign-in page for you.
Publish index.html, style.css, powerups.js, sim.js and game.js with publish_game, which gives you a share link at https://<your-game>.play.multiplayeragent.com/.

The free tier is enough to play with friends.

Project structure

File	What it does
game.js	Browser client: rendering, input, prediction and interpolation, accounts, leaderboards, menus
sim.js	Game rules shared by server and client: movement, food, power-ups, bullets, collisions, bot AI
powerups.js	Weapon and power-up definitions and their icons
server/logic.js	Authoritative room logic: inputs, ticks, state sync, events, saves and leaderboard scores
build.js	Bundles `powerups.js` + `sim.js` + `server/logic.js` into `dist/server.js` for deployment
index.html, style.css	Page, HUD and menus