client/overview/tech.md

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.

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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

# 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

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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)