# Tech Stack

## Engine & Language

- **Engine:** Godot 4.7 (Forward Plus renderer)
- **Language:** GDScript
- **Project path:** `/mnt/code/spacewar/spacewar/` (inner folder is the Godot project root)
- **Platform target:** Linux (Steam Deck native, 1280×800), Windows PC
- **Art style:** Pixel art (placeholder sprites in use currently)

See `structure.md` for the full file tree and scene graph.

---

## Multiplayer Architecture (Planned)

```
[Client] ──── [Matchmaking Server] ──── [Dedicated Game Server]
                      │
               [Backend API]
               (queue, ranks, accounts)
```

### Authoritative Server Model

- Dedicated game servers run the authoritative simulation (not player-hosted)
- Clients send **inputs** (movement, fire, ability) — server validates and broadcasts results
- No client-side cheating possible on critical state (position, HP, kills)
- Player position simulated server-side; clients predict locally and reconcile

### Godot Networking Layer

```gdscript
# Server: move a player
@rpc("authority", "call_local", "reliable")
func set_position(new_pos: Vector2) -> void:
    position = new_pos

# Client: send input to server
@rpc("any_peer", "call_remote", "unreliable")
func send_input(dir: Vector2, firing: bool) -> void:
    pass
```

- **Transport:** ENet (UDP, built into Godot) for low-latency game data
- **Reliable channel:** critical state (HP, death, respawn)
- **Unreliable channel:** high-frequency position/velocity updates

### Client-Side Prediction & Lag Compensation

1. Client predicts own movement locally (feels instant)
2. Server confirms or corrects (reconciliation)
3. Other players interpolated between last two known positions
4. Lag compensation: server rewinds state slightly to validate hitscan shots

### Matchmaking Backend

| Component | Tech |
|-----------|------|
| API Server | Go or Node.js |
| Queue / State | Redis |
| Database (accounts, ranks) | PostgreSQL |
| Hosting | VPS (Hetzner / DigitalOcean) or self-hosted |

**Flow:**
1. Client sends "find match" with MMR + mode
2. Backend queues player, finds lobby within MMR range
3. Lobby full → backend assigns a game server
4. Backend sends client the server IP + session token
5. Client connects directly to game server

### Steam Integration

- **GodotSteam** plugin (open source, wraps Steamworks SDK)
- Handles: Steam auth, VAC anti-cheat, Steam lobbies, achievements
- No separate account system needed at launch

---

## Networking Checklist

- [ ] Godot ENet server/client setup
- [ ] Player input RPC structure
- [ ] Position sync with interpolation
- [ ] Ship class registration per peer
- [ ] Server-authoritative health/death
- [ ] Matchmaking API (queue + lobby assignment)
- [ ] GodotSteam auth + VAC
- [ ] Lag compensation (basic rewind)