A marble game that generates its own levels

lost-your-marbles is a physics sandbox that turned into a game: you push a marble through procedurally generated levels on a sixty-second timer, in Rust on Bevy 0.14 with Rapier for the physics.

The pipeline is the interesting part, and it’s the reason the greedy mesher has a home — that article’s code isn’t a separate toy, it’s src/greedy_mesher.rs in this repo. Levels start as tile grids from levelgen/, become voxel grids, get merged into optimised triangle meshes, and only then become physics colliders. Tiles are Floor, Wall, Slope, StartArea, EndArea, Obstacle, and there’s a whole levelgen/graph/ pipeline — generator, refinement, validator — plus wave function collapse in prefab/wfc.rs for assembling track pieces.

The part I didn’t expect: the game runs an HTTP server on 8080 and a WebSocket on 8081, streaming marble state at 60 FPS and taking commands as JSON. Which exists because there’s a Python AI player that plays it — ai_player_vision.py connects over the socket, gets a deliberately limited vision radius, keeps a memory of visited tiles, and drives the marble by posting world-axis forces. The game made itself remotely controllable so something else could learn to play it.

There are also enemy marbles with a four-state mind — wandering, chasing, searching, stunned — that lose track of you behind walls, because line-of-sight checks run against the tile grid and x_ray_vision defaults to false.

Reading the log, camera work dominates: eighteen of the eighty-five commits touch it, and there’s camera.rs, camera_zones.rs, levelgen/camera_analysis.rs and a docs/camera-modes.md. Zone-based tracking, slope-aware distance clamping, an intro pan that follows the solution path along a spline. Which makes sense for a rolling marble in generated terrain — the level is only solvable if you can see it — but I don’t think I’d have guessed the camera would be the biggest single line item.

Eighty-five commits between September 2025 and the 1st of April, when a game-controller support commit landed and it went quiet.

Related: the-meadow-grew-a-map — the other Rust-and-Bevy world here.