Coup Online

Play Game

Overview

A real-time multiplayer implementation of the card game Coup. The frontend is a React web application built with Material UI and Vite. The app communicates with the backend Express server via the WebSocket protocol (using Socket.IO), falling back to the HTTPS protocol if the socket connection fails. Game state is stored in a Redis database. Authentication is handled via Firebase (Google sign-in).

Features

• Real-time multiplayer gameplay with WebSocket communication
• AI opponents with strategic decision-making
• In-game chat
• User profiles and leaderboard
• Multi-language support
• QR code game invites

Project Structure

This is a pnpm monorepo with three packages:

• client — React 19 single-page application
• server — Express 5 API and Socket.IO server
• shared — TypeScript types, game logic, and helpers used by both client and server

Internationalization

New languages can be added by doing the following:

1. Define the new language in shared/i18n/availableLanguages.ts
2. Add client translations in client/src/i18n/translations.ts
3. Add server translations in server/src/i18n/translations.ts

Deployments

Deployments are automated. To deploy a new version of the game, simply create a new Release.

Environment Variables

Server

Variable	Description	Default
EXPRESS_PORT	Port the server listens on	8008
REDIS_CONNECTION_STRING	Redis connection URL	—
FIREBASE_SERVICE_ACCOUNT_KEY	Firebase Admin service account JSON	—
FIREBASE_PROJECT_ID	Firebase project ID	—

Client

Variable	Description	Default
VITE_API_BASE_URL	Server API URL	http://localhost:8008
VITE_SOCKET_SERVER_URL	WebSocket server URL	http://localhost:8008
VITE_SOCKET_SERVER_PATH	WebSocket path	""
VITE_FIREBASE_API_KEY	Firebase API key	—
VITE_FIREBASE_AUTH_DOMAIN	Firebase auth domain	—
VITE_FIREBASE_PROJECT_ID	Firebase project ID	—
VITE_FIREBASE_STORAGE_BUCKET	Firebase storage bucket	—
VITE_FIREBASE_MESSAGING_SENDER_ID	Firebase messaging sender ID	—
VITE_FIREBASE_APP_ID	Firebase app ID	—

Running Locally

Run Server

cd server
pnpm i
pnpm dev

Run Client

cd client
pnpm i
pnpm start

Run Server Tests

Server needs to be running for integration tests

cd server
pnpm test

Run Client Tests

cd client
pnpm test
pnpm cypress open