Speedrun a small multiplayer flight prototype by fixing the minimum scene and control contract, getting one local player working, adding an authoritative WebSocket loop in a separate workstream, and testing synchronization and failure behavior before adding polish.
Source episode · 10:00
How I AI: Speedrun a 3D Multiplayer Game in 15 Minutes with Cody De Arklandwith Claire Vo
Cody initializes a project with Claude Code, asks for a polygon style Three.js flight simulator with movement, banking, and pitch controls, runs the first build, diagnoses reversed orientation and controls, starts an Express and WebSocket multiplayer server in parallel, and tests several connected players within the live demo.
A local multiplayer prototype where several clients join, move distinct aircraft, see synchronized state, disconnect cleanly, and recover from common errors, with known hacks and production gaps clearly recorded.
Anthropic AI assistant
Claude for coding tasks
Step by step
Follow the sequence once, then adapt the prompts, checks, and handoffs to your own setup.
6 steps
Initialize the repository and have Claude Code inspect the framework, scripts, and structure. Create a concise project guide with client and server commands, file boundaries, coordinate conventions, and checks.
npm create vite@latest your-game-name -- --template react cd your-game-name claude init --yolo
Specify the smallest flight loop: Three.js scene, licensed low polygon aircraft, coordinate system, forward axis, controls, camera, speed, world boundary, and visual feedback.
Build the first local slice of a low polygon Three.js flight simulator. Coordinate system: [axes and forward]. Controls: [mapping]. Camera: above and behind the model. Implement movement, bank, pitch, speed, boundary, and a debug axis helper. Use the licensed model at [path] and document its native orientation and transform. No multiplayer yet.
Run the first version and debug behavior with observable facts such as axis direction, model transform, camera position, and input mapping. Fix one coordinate issue at a time and keep the debug helper until flight is correct.
It looks like my camera is facing the front of the model... we should be looking should be fixed to the tail of the plane. All of my flight controls are reversed. Now we should fix that. I also want the camera to be slightly above and behind the model.
Create a separate server workstream with Express and WebSockets after the local loop works. Define shared message types and a thin join, input, state, and disconnect protocol before building more features.
In the `server` directory, build a multiplayer backend for my game. Use Node.js, Express, and Socket.io. The server must handle the following: - Player connections and disconnections. - Broadcasting player movement data to all connected clients. - [Describe any additional features, like a chat system or player list]. Generate all necessary files and install dependencies.
Ask the backend agent to assign player IDs, validate bounded input messages, run a fixed tick, broadcast accepted state, and remove disconnected or timed out players.
Implement the multiplayer server for this protocol: [shared types]. The server assigns IDs, validates message schema, size, rate, numeric ranges, and sequence, updates authoritative state at [tick rate], broadcasts snapshots, and cleans up disconnects and heartbeat timeouts. Add tests for malformed messages, duplicate joins, abrupt disconnect, and reconnect.
Launch server and at least two independent browser clients. Test distinct identities, movement, visibility, disconnect, reconnect, latency, cleanup, and malformed traffic, then record known limitations before adding chat, persistence, or public hosting.
Turn an idea into a PRD, user stories, and a plan.
After the steps
How to recover when the loop fails and where human judgment helps.
Recover
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