Duck Sort (working title: "Ducks")

Duck Sort is a small experimental game about sorting points on a plane. The points are thematically called "ducks." The goal is to design a playful, tactile experience with realistic motion and multiplayer collaboration.

Live demo: Play the demo

Gameplay

Terminology:

• "Wolves" — white points controlled indirectly by players; they chase the active player's cursor with inertia.
• "Ducks" — colored points that bounce off wolves with physical inertia.

Rules and flow:

1. Wolves follow the current player's cursor with a delayed, inertia-driven movement.
2. Ducks bounce away from wolves and retain momentum according to the physics simulation.
3. The number of simultaneously active wolves per room is limited by configuration (max 4).
4. When all ducks of a given color cluster within a contiguous area that contains no other colors, that area is considered that color's zone.
5. The game is won when every color has its own zone.
6. On win, show: "You sorted the ducks in XX.XX seconds".
7. A timer runs during gameplay. It starts when the first player initiates the game. Late joiners do not affect the timer.

Highlights

• Multiplayer sessions via room ID or shareable link
• Runs in the browser (web app rendering)
• Cross-platform potential with a React Native mobile app
• Physics-driven interactions: points respond to drag-and-drop inertia and momentum

Technology stack (accepted)

• Frontend: Vanilla JS/TS
• Physics and render: Matter.js
• Networking: WebRTC DataChannel ("star"-host) for low-latency duck snapshots
• Signaling/presence/cursors: Firebase Realtime Database (RTDB)
• Authentication: Anonymous (Firebase Auth)
• Hosting: Github Pages

Architecture overview

• Host-authoritative, peer-to-peer: one client is elected host and runs the physics simulation.
• Low-latency data plane: host broadcasts duck snapshots to peers over WebRTC DataChannels (~10 Hz). Guests interpolate.
• Signaling and coordination: Firebase RTDB is used for:
  • Host election and migration (rooms/{roomId}/hostId)
  • Presence (rooms/{roomId}/peers/{uid})
  • Cursors (rooms/{roomId}/cursors/{uid}) at ~20 Hz
  • WebRTC signaling messages (rooms/{roomId}/signals/{from}/{to}) with pruning and onDisconnect cleanup
• No custom server required. RTDB rules restrict writes (per-user presence/cursors, signaling sender/recipient) and allow host cleanup.
• Reliability: glare handling and signaling-state guards to avoid invalid SDP states; periodic pruning of stale signaling branches.

Monorepo layout

This repository is organized as a monorepo with the following packages:

• common/ — shared code reused by server, web, and mobile
• server/ — backend package (reserved for future needs). Not required for the initial Firebase-based P2P sync.
• web/ — browser client: game logic and rendering in the web app
• mobile/ — React Native app: cross-platform client with game logic and rendering

Status

Planning and structure in progress. See the ADR for architecture decisions:

• docs/adr/0001-architecture.md
• docs/adr/0002-p2p-firebase-sync.md
• docs/adr/0003-webrtc-rtdb-signaling.md

🪲 Known Issues & Limitations

• WebRTC: connection not established on some devices/networks

  Symptoms: DataChannel stuck in connecting, iceConnectionState = checking ~20+ seconds, ondatachannel not working, logs like [ICE] ice=new conn=new pair=undefined sctp=undefined dc=connecting.

  Possible causes: missing TURN for symmetric NAT, old/corporate browsers with ICE/mDNS restrictions, different network policies, sometimes glare when initiated simultaneously.

  Status: playable on old laptop, stable on modern browsers.

• Multiplayer: interpolation “jerks”

  Positions jump (rubber-banding) noticeable during packet loss or FPS differences. Better state buffer and velocity blending needed.

• Differences between animations and demo video

  Inertia/damping/rebound parameters are not yet proven “for video”. It takes time to select configs.

• Host migration edge-cases

  If the host suddenly exits, a short desync is possible and the reconnection is not always neat.

• UI/lobby not finished

  Players connect directly via link; config panel and full lobby are still in development.

🚀 Running Locally

# install dependencies
npm install

# run web client in ./web
npm run dev --workspace=web

# optionally, start Firebase emulator for testing in ./infrastructure/firebase
firebase emulators:start

Deployment GitHub Pages

Deploy the web app to GitHub Pages or any static hosting service:

cd web
npm run build:prod
rm -rf ../example/web/*
cp -r dist/* ../example/web