Multiplayer Card Game

Project Overview

Multiplayer Card Game is a real-time online card game built for Android, designed to support smooth multiplayer gameplay using a custom Socket.IO client–server architecture.

The project integrates Firebase Authentication for secure user login, Firebase Cloud Messaging for real-time notifications, and social invite flows to improve player engagement and retention.

My Role & Responsibilities

• Designed and implemented real-time multiplayer architecture using Socket.IO
• Built client-side networking layer in Unity (C#)
• Integrated Node.js backend for room management and game state handling
• Implemented turn-based game flow with server-authoritative validation
• Handled player join, disconnect, and reconnection scenarios
• Optimized network message payloads to reduce bandwidth usage
• Ensured fair gameplay by preventing client-side state manipulation
• Integrated Firebase Authentication with Google and social sign-in providers
• Implemented Firebase Cloud Messaging for match invites and game notifications
• Built social invite sharing via WhatsApp and native platform share intents
• Linked authenticated users with multiplayer sessions securely

Engineering & System Design

Client–Server Multiplayer Architecture

The game uses a centralized server model where the backend acts as the single source of truth for game state, ensuring consistency and fairness.

• Server-managed rooms and player sessions
• Authoritative turn validation on the backend
• Event-driven communication using Socket.IO

Firebase Authentication & Player Identity

Firebase Authentication was used to provide secure and frictionless login using Google and social providers, allowing players to persist identity across sessions and devices.

• Token-based authentication for backend validation
• Seamless account recovery and session persistence

Push Notifications & Social Invites

Firebase Cloud Messaging enables push notifications for game events such as match invites, turn reminders, and re-engagement prompts.

• Match invite notifications via FCM
• Deep-link support for opening game rooms
• Social sharing through WhatsApp and platform-native share APIs

Network Optimization

Reduced unnecessary data transmission by sending only essential state updates instead of full game state snapshots on every action.

Challenges & Solutions

Challenge: Secure multiplayer access and identity management

Multiplayer games require trusted player identity to prevent impersonation and abuse.

Solution: Integrated Firebase Authentication and validated authenticated user tokens on the backend before allowing multiplayer actions.

Challenge: Maintaining game state consistency in real-time

With multiple players performing actions concurrently, maintaining a single, authoritative game state was critical.

Solution: Implemented server-authoritative logic where the backend validates every move and emits synchronized events to all clients.

Media

🎥 Gameplay Video