Multiplayer: shared-physics playground

capstone lesson Advanced ⏱ 20 min vgai 0.1.0

Prerequisites: Manual — Networking · Multiplayer — Colyseus rooms

What you'll learn

• Run a server-authoritative shared-physics game on a Colyseus room
• See players and pushable boxes sync from the server, not P2P
• Understand server-owned object state with the Callbacks API

What you'll build: A shared-physics arena where your avatar and dynamic boxes are simulated on the server and synced to every client.

Walkthrough — Multiplayer: shared-physics playground · generated by site/media/lessons/tierc-mp-batch.lesson.ts (4 steps)

Notblox’s signature is a shared physics world: every player moves a server-owned avatar and pushes dynamic boxes, and every client renders the same synced positions. Object state lives on the server, not peer-to-peer — so two clients never disagree about where a box is. This port keeps that essence with a light 20 Hz server sim (NotbloxRoom) and the Colyseus Callbacks API on the client.

Steps

1. Open the notblox scene. Load examples/scenes/notblox.vscn.json.

   

   The shared-physics arena, ready to run.

2. Enter play mode — the client joins the notblox room. The example connects to notblox_room and registers Callbacks (onAdd/onChange/onRemove) for players and boxes.

   

   The client connects to notblox_room.

3. Server-authoritative players and boxes sync. The HUD reads room state live — ● online · 4 players · 5 boxes. The capsule avatars and crates are positioned from server state every frame; the server integrates input and box pushes, then broadcasts.

   

   Avatars + boxes rendered from synced server state (4 players, 5 boxes).

4. Stop play mode. Press Stop (or Escape) — the room connection closes.

Why server-authoritative, not P2P

The room owns the boxes: a player within PUSH_RADIUS imparts PUSH_FORCE, boxes slide with BOX_FRICTION and stay inside ARENA_HALF, all in the server’s SIM_INTERVAL_MS tick (server/rooms/notblox-room.ts). Clients only render the synced x/z — so every client agrees on the world. That’s the difference from peer-to-peer: there is one authority.

Read live schema in callbacks

Per the Colyseus v0.17 contract, read schema fields inside onChange (don’t destructure them into locals) so you always render the latest server value. See Multiplayer — Colyseus rooms.

Recap

New functionality

• Ran a server-authoritative shared-physics game
• Saw players and boxes sync from the server (4 players, 5 boxes)

New concepts & skills

• Object state is server-owned, not P2P — one authority, no disagreement
• The server ticks at SIM_INTERVAL_MS; clients render synced positions
• Callbacks (onAdd/onChange/onRemove) drive client rendering from room state

Next lesson → Multiplayer: tank arena

See also

• Networking · Colyseus rooms · Tank arena