wtf is marble-runner?

Marble Runner is a small browser game that lets you walk around inside a Gaussian splat world in third-person. A Gaussian splat is a relatively new way of representing a 3D scene from photographs, popularized in 2023, that produces very photo-real results. World Labs is a company that runs Marble, a service for generating such worlds. This project takes a Marble world file and drops a controllable character into it so you can walk, run, and jump through the scene. The README points to a hosted version at marble-runner.vercel.app where you can play without installing anything. You pick one of five default worlds, choose a character, or make your own using the Avaturn avatar creator in about a minute. Movement is the standard WASD plus Shift to run and Space to jump, with mouse drag for the camera and Tab to open a debug panel. If you have generated your own world in Marble, the README suggests an unusual onboarding path: open Claude Code and paste a prompt that tells the AI assistant to clone the repo, install dependencies, start the dev server, and set up your splat file under a chosen name. The assistant creates a folder under public/worlds, copies the .spz splat file in, scaffolds a flat physics collider so the character has something to stand on, writes a meta.json, and restarts the server. The project is built with TypeScript and Vite. Rendering uses Three.js with Spark 2.0 from World Labs to handle the splat format. Physics uses Rapier3D with a kinematic character controller. Character models are standard Mixamo GLB files with idle, walk, run, and jump animations. The license is MIT, and the README notes Mixamo characters are free for commercial use.