# Multiplayer

> Multiplayer game development principles. Architecture, networking, synchronization.

- Skill: `yunaamelia/multiplayer` (Agent Skill)
- Install (CLI): `npx skillmds add yunaamelia/multiplayer`
- Raw SKILL.md: https://api.skillmd.com/api/skills/yunaamelia/multiplayer/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: yunaamelia (https://skillmd.com/u/yunaamelia)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/yunaamelia/multiplayer

---


# Multiplayer Game Development

> Networking architecture and synchronization principles.

---

## 1. Architecture Selection

### Decision Tree

```
What type of multiplayer?
│
├── Competitive / Real-time
│   └── Dedicated Server (authoritative)
│
├── Cooperative / Casual
│   └── Host-based (one player is server)
│
├── Turn-based
│   └── Client-server (simple)
│
└── Massive (MMO)
    └── Distributed servers
```

### Comparison

| Architecture   | Latency  | Cost | Security |
| -------------- | -------- | ---- | -------- |
| **Dedicated**  | Low      | High | Strong   |
| **P2P**        | Variable | Low  | Weak     |
| **Host-based** | Medium   | Low  | Medium   |

---

## 2. Synchronization Principles

### State vs Input

| Approach       | Sync What     | Best For            |
| -------------- | ------------- | ------------------- |
| **State Sync** | Game state    | Simple, few objects |
| **Input Sync** | Player inputs | Action games        |
| **Hybrid**     | Both          | Most games          |

### Lag Compensation

| Technique            | Purpose                  |
| -------------------- | ------------------------ |
| **Prediction**       | Client predicts server   |
| **Interpolation**    | Smooth remote players    |
| **Reconciliation**   | Fix mispredictions       |
| **Lag compensation** | Rewind for hit detection |

---

## 3. Network Optimization

### Bandwidth Reduction

| Technique             | Savings              |
| --------------------- | -------------------- |
| **Delta compression** | Send only changes    |
| **Quantization**      | Reduce precision     |
| **Priority**          | Important data first |
| **Area of interest**  | Only nearby entities |

### Update Rates

| Type      | Rate      |
| --------- | --------- |
| Position  | 20-60 Hz  |
| Health    | On change |
| Inventory | On change |
| Chat      | On send   |

---

## 4. Security Principles

### Server Authority

```
Client: "I hit the enemy"
Server: Validate → did projectile actually hit?
         → was player in valid state?
         → was timing possible?
```

### Anti-Cheat

| Cheat      | Prevention                  |
| ---------- | --------------------------- |
| Speed hack | Server validates movement   |
| Aimbot     | Server validates sight line |
| Item dupe  | Server owns inventory       |
| Wall hack  | Don't send hidden data      |

---

## 5. Matchmaking

### Considerations

| Factor         | Impact              |
| -------------- | ------------------- |
| **Skill**      | Fair matches        |
| **Latency**    | Playable connection |
| **Wait time**  | Player patience     |
| **Party size** | Group play          |

---

## 6. Anti-Patterns

| ❌ Don't             | ✅ Do                |
| -------------------- | -------------------- |
| Trust the client     | Server is authority  |
| Send everything      | Send only necessary  |
| Ignore latency       | Design for 100-200ms |
| Sync exact positions | Interpolate/predict  |

---

> **Remember:** Never trust the client. The server is the source of truth.