Multiplayer Wave Survival Game Backend

Overview

This project is a real-time multiplayer backend for a cooperative survival game.

Players join a room, wait in a lobby, and then survive waves of enemies together. The system is designed to handle multiple rooms with many concurrent players.

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Features

• Room-based multiplayer (max 50 players per room)

• 30-second lobby countdown before game start

• Cooperative gameplay (players vs enemy waves)

• 2 waves of enemies (10 enemies each)

• Increasing difficulty per wave

• Real-time state updates using WebSockets

• Group-based result:

  • WIN → at least one player survives all waves
  • LOSE → all players die

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Game Flow

Join Room → Lobby (30s) → Game Start → Waves → Result

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Core Events

Client → Server

• JOIN_ROOM

Server → Client

• JOIN_SUCCESS → returns roomId
• LOBBY_TIMER → countdown updates
• GAME_START → game begins
• GAME_STATE_UPDATE → real-time state
• PLAYER_ELIMINATED → player dies
• GAME_END → WIN / LOSE

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Project Structure

game-backend/
├── src/
│   ├── server.js
│   ├── gateway/
│   │   └── socketHandler.js
│   ├── rooms/
│   │   ├── room.js
│   │   └── roomManager.js
│   ├── game/
│   │   └── gameEngine.js
│
├── public/
│   └── index.html
│
├── package.json
└── README.md

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Tech Stack

• Node.js
• Socket.IO
• HTML Canvas (for demo UI)

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Run Locally

npm install
node src/server.js

Open:

public/index.html

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How to Test

• Open multiple tabs in browser

• Each tab = one player

• Observe:

  • lobby countdown
  • wave progression
  • player elimination
  • final result

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Design Choices

Why 50 players per room?

• Balances performance and gameplay
• Avoids heavy CPU/network load
• Ensures smooth real-time updates

Why server-authoritative?

• Single source of truth
• Prevents inconsistent state
• Simplifies synchronization

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Notes

• Players cannot join after game starts
• New players are assigned to a new room
• Game runs entirely in memory for speed

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Implementation Notes

This project demonstrates:

• Room-based player grouping
• Real-time state synchronization
• Tick-based simulation loop
• Wave-based enemy system
• Controlled game lifecycle (lobby → game → end)

The implementation validates a scalable and maintainable multiplayer backend design.

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Future Improvements

• Add player-controlled movement
• Add projectile-based combat
• Add reconnect handling
• Add distributed state (Redis)
• Add matchmaking strategies

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Author

Laiba Firdouse