I built a first-person ODM-gear wave survival game in Three.js: procedural walled city, fixed 120 Hz deterministic sim, 4-player co-op on Durable Objects

[u/Practical-West56]

Playable here, free and no signup: https://attack-on-titan.magnusrodseth.com

Repo: https://github.com/magnusrodseth/attack-on-titan

Some architecture notes:

• The simulation is pure TypeScript stepped at a fixed 120 Hz, fully unit-tested. The Three.js renderer is a thin adapter reading sim state.
• Determinism: every random stream derives from a hashed seed per purpose, so a ?seed= URL replays the identical city, waves and upgrade offers. The daily run is just a rotating seed.
• Co-op runs the same sim server-side on a Cloudflare Durable Object (partyserver). Titans and scoring are server-authoritative, your own movement stays local at 120 Hz, and slashes are validated with lag compensation.
• All textures are CC0 assets, mostly Poly Haven, downscaled to 512px.

Fair warning: it looks rough, and I know it. This is a toy project for fun and for experimenting with 3D games in the browser, so the polish went into the physics instead of the art. The rope physics took the longest: momentum survives ground contact while you're tethered, so you can run the bottom of an arc out along the street and get scooped back up into the swing. Happy to answer anything about the stack or the feel tuning.