Starfall

A Homeworld-style, universe-scale space RTS that runs in a browser.

▶ Play it · the prompt it came from · build thread

Written by Claude Opus 5 driving a multi-agent workflow, from a single prompt. No design document, no asset list, no architecture was specified up front — the prompt is reproduced in full in prompt.md.

First run: ~$633 — 68.6k input tokens, 4.6M output, 837.2M cache read, 13.6M cache write.

Not one, anywhere in the build. Every hull, texture, planet, star field, nebula and effect is generated at runtime from code:

• Hulls are lofted from authored cross-sections, then dressed by a budget-driven pass that spends its remaining triangle allowance on plate steps, greebles, catwalks and window rows sampled off the lofted skin. A density field decides where detail must be absent, because the difference between a warship and a noise field is that a warship has quiet armour to contrast against its machinery.
• Surfaces are triplanar procedural detail at three scales — armour blocks, plating, rivets — with the tile size scaling to hull radius, so a 2.1 km mothership is not panelled in the same 6 m plates as a 27 m interceptor.
• Planets are fBm noise with an atmosphere shell; the sky is a procedural nebula baked to a cube map, which then feeds the PMREM environment lighting, so the ships are genuinely lit by the sky they sit in.

The only imported assets are audio, and all of it is CC0 — see the in-game credits (CREDITS in the top bar, or F1).

• Thirteen ship classes, from a scout to a two-kilometre mothership
• Three-dimensional movement with the Homeworld move disc: right-drag vertically to dial the altitude of an order
• Formations, stances, control groups, a fleet roster bar, band select and hull-accurate picking
• Production, research, resource harvesting and an opponent AI
• Drive plumes with shock diamonds, wakes that curve through a manoeuvre, ion lances, kinetic tracers, shields and multi-stage detonations
• A streamed score that follows the intensity of the fight

npm install
npm run build     # tsc --noEmit && vite build
npm run preview   # serves dist on :4173

Needs a browser with WebGL 2.

Contract-first, so the subsystems could be built independently:

Rendering is decoupled from simulation and never mutates it. Ships draw through one InstancedMesh per (class, LOD, variant) bucket plus impostor billboards at range, so a fleet of hundreds holds frame rate.

scripts/ is worth a look if you are curious how a model verifies its own visual work: capture.mjs drives a headless browser and shoots frames, probe.mjs evaluates arbitrary expressions against the live scene, pnginfo.mjs reads histograms back out of the screenshots, and inputtest.mjs measures what each mouse gesture actually did to the camera. Almost every fix in the history was found with one of them rather than by reasoning about the code.

In tribute to Homeworld (Relic Entertainment, 1999) — the game that decided a fleet should be a shape in three dimensions, that a wake should tell you which way a contact is breaking, and that silence and a horizon line are worth more than any amount of noise. Starfall is an independent homage and uses none of its art, audio, code or trademarks.

The prompt is a modified version of Matt Shumer's one-shot AAA prompt.

Music from OpenGameArt (Tozan, yd, wipics, vitalezzz, Synth-thetic, CleytonKauffman); sound effects from Kenney. All CC0.

Built with three.js, Vite and TypeScript.

By Mike Luan at e01.ai.

MIT.