Snatch or Share: A Game of Governance

App-Based Multiplayer Game Inspired by Elinor Ostrom

Overview

Snatch or Share is a mobile-based multiplayer game that lets participants experience how rules, trust, and institutional arrangements affect cooperation in decentralized exchanges. Based on Elinor Ostrom's "Snatch Game" (from Understanding Institutional Diversity), it's designed for workshops to simulate the evolution of governance in public goods settings — like those needed for EUDR compliance.

Participants and Grouping

• Players sign in with their real names
• The system randomly assigns players into 2-person groups (Group 1 to Group N)
• Each group plays through five rounds of structured interaction
• A shared plenary dashboard shows all groups in parallel for debriefing

What Are Tokens and Points?

Tokens = Tradable Goods

Each player starts with 10 tokens of a specific good:

• Either Turkeys or Ears of Corn

Tokens represent units of what the player produces (e.g. a household with 10 turkeys)

Points = Value of What You Hold

Each player values goods differently:

• Their own tokens = 1 point each
• The other player's tokens = 2 points each

So:

Scenario	Points
Holding 10 of your own	10 points
Holding 5 of own + 5 of other	15 points
Holding 10 of own + 5 snatched	20 points

Tokens are used in gameplay (offered, accepted, snatched). Points are calculated after each round based on the player's inventory. The goal is to maximize point value through strategic decisions.

Game Progression (5 Variants)

G1: State of Nature

• All players are Traders. No enforcement or roles
• Player 1 (P1) is prompted to offer a trade
• Player 2 (P2) responds:
  • Accept → both exchange tokens → each ends with ~15 points
  • Refuse → no trade → each stays at 10 points
  • Snatch → snatcher takes offer without paying → 20 points; offerer left with 5

No trust = no cooperation = suboptimal outcomes

G2: Counterproductive Rule

• New rule: "P2 can force P1 to make an offer"
• Players still have freedom to snatch
• Reduces agency, invites exploitation

G3: Soft Norms (Shame Tokens)

• P1 can assign 1 shame token after being snatched
• Shame tokens accumulate across games
• Social deterrents emerge, but without enforcement may be inconsistently applied

G4: Minimal Property Rights

• P1 can report a snatch to the system
• If confirmed:
  • Goods are returned to P1
  • P1 also receives what was requested (compensation)

Governance stabilizes expectations → trust emerges

G5: Cheap Talk

• P1 can send a pre-round message to P2 before making an offer
• Tests whether communication alone improves cooperation

System Diagrams

The game logic is documented in Mermaid diagrams:

Diagram	Description
game-overview.mmd	High-level game flow
game-sequence.mmd	Detailed sequence diagram
game-state-machine.mmd	State transitions
data-model.mmd	Data structures
g1-no-property.mmd	G1 variant flow
g2-counterproductive-rule.mmd	G2 variant flow
g3-shame-token.mmd	G3 variant flow
g4-min-property-rights.mmd	G4 variant flow
g5-cheap-talk.mmd	G5 variant flow
matchmaking.mmd	Matchmaking logic
tournament-orchestration.mmd	Tournament flow

System Capabilities

Real-Time Multiplayer

• WebSocket-based communication using Colyseus.js
• Server-authoritative state management
• Automatic reconnection with session persistence
• 60Hz update rate for real-time feel

Player Management

• UUID-based player identification
• Persistent player names and colors
• Shame token tracking across sessions
• Automatic matchmaking into game rooms

Game Control (Admin Dashboard)

• Room Management: Create, pause, resume, restart games
• Player Control: Kick players, view stats per room
• Global Controls:
  • Pause/resume all games simultaneously
  • Change game variant (G1-G5) globally
  • Shuffle players between rooms
  • Send all players to lobby
• Real-time Monitoring: CCU, room status, player actions

Data & Analytics

• Server-Sent Events (SSE) for live dashboard updates
• Export/import game state (.snatchSave format)
• Event logging with filtering capabilities
• Leaderboard with score calculations

Deployment

• Docker containerized deployment
• Nginx reverse proxy support
• SSL/TLS integration

Tech Stack

Layer	Technology
Backend	Node.js, Colyseus.js, Express, TypeScript
Frontend	Vue 3, Vite, TypeScript
Real-time	WebSockets (uWebSockets)
State	Colyseus Schema (delta compression)
Deployment	Docker, Nginx

Project Structure

snatchgame/
├── server/                 # Backend Colyseus server
│   ├── src/
│   │   ├── rooms/          # Game and Lobby rooms
│   │   ├── schemas/        # State schemas
│   │   ├── utils/          # Utilities (name manager)
│   │   ├── adminApi.ts     # Admin REST API
│   │   └── index.ts        # Server entry point
│   └── package.json
│
├── client/                 # Frontend Vue application
│   ├── src/
│   │   ├── views/          # Vue components
│   │   ├── services/       # Colyseus client service
│   │   ├── router/         # Vue Router
│   │   └── main.ts         # App entry point
│   └── package.json
│
├── deploy/                 # Deployment configurations
│   ├── Dockerfile          # Docker image build
│   ├── dockerignore        # Files to ignore in build
│   └── start.sh            # Container startup script
│
├── *.mmd                   # Mermaid diagrams
└── shared/                 # Shared types

Quick Start

# Install dependencies
npm run install:all

# Start development (server + client)
npm run dev

URLs (Development)

• Game: http://localhost:5173
• Admin Dashboard: http://localhost:5173/dashboard
• Colyseus Monitor: http://localhost:3000/colyseus
• API: http://localhost:3000/api

API Endpoints

Endpoint	Description
GET /api/rooms	List all active rooms
GET /api/rooms/:id/stats	Room statistics
POST /api/rooms/:id/pause	Pause a game
POST /api/rooms/:id/resume	Resume a game
POST /api/rooms/:id/restart	Restart a game
POST /api/admin/pause-all	Pause all games
POST /api/admin/shuffle-players	Redistribute players
GET /api/admin/namemanager/export	Export state
GET /api/dashboard-stream	SSE dashboard updates

Acknowledgments

This project was commissioned by the Alliance of Bioversity International and CIAT (CGIAR) for educational workshops on governance and cooperation.

Project Sponsors:

• Federico Ceballos - Alliance Bioversity-CIAT
• Brian King - Alliance Bioversity-CIAT

Developer:

• José Darío - Nucleo Rio Frio

Based on Elinor Ostrom's "Snatch Game" from Understanding Institutional Diversity.

License

MIT License - See LICENSE file for details.

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Developed by José Darío for educational workshops on governance and cooperation.