Initial commit before folder reorganization

Checkpoint of the existing flat file layout prior to restructuring
into autoload/, menu/, ships/, world/, and assets/ folders.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

overview/tech.md

@@ -0,0 +1,89 @@
+# 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)