galaxy-gen

{ rust → wasm → js } galaxy generation simulation. Gravitational physics (Newton's law on a cell grid) computed in Rust, compiled to WebAssembly via wasm-pack, rendered in the browser with React + D3.

Quick start

make install     # cargo build + wasm-pack + npm install + playwright browsers
make dev         # rust/wasm watcher + webpack-dev-server (dual auto-reload)
make test        # rust unit tests + Playwright E2E

See the makefile for the full set of targets and AGENTS.md for the conventions.

Architecture

• src/rust/galaxy.rs — core simulation (Galaxy + Cell structs, cell types Gas / Star / Planet / White Hole, gravity, seeding, tick). Unit tests live in mod tests_* blocks at the bottom of the file.
• src/rust/lib.rs — crate root; re-exports galaxy.
• pkg/ — wasm-pack output: .wasm + .js + .d.ts. Gitignored; linked into node_modules/galaxy_gen_backend by npm install ./pkg.
• src/js/lib/galaxy.ts — Frontend class; the JS ↔ WASM boundary.
• src/js/lib/application.tsx — React UI (inputs, buttons, data-testids).
• src/js/lib/dataviz.tsx — D3 scatter plot into #dataviz.
• src/js/lib/styles.css — Tailwind v4 + custom coilysiren palette.
• e2e/galaxy.spec.ts — Playwright end-to-end tests.
• dist/ — production webpack build output (gitignored).

Tooling

• Rust: cargo check / cargo test / cargo fmt / cargo clippy.
• WASM: wasm-pack build compiles Rust to WebAssembly. The dev server watches pkg/**/* and hot-reloads on rebuild (via cargo watch).
• JS: webpack 5 + babel (React + TypeScript presets). Tailwind v4 via PostCSS.
• Lint/format: ESLint flat config (eslint.config.mjs) + Prettier.
• Tests: Rust unit tests via cargo test; browser end-to-end via Playwright (npm run test:e2e).
• CI: GitHub Actions runs rust, js, and e2e jobs on every push/PR to main.

Similar projects

Open-source galaxy / n-body / WASM-sim projects worth studying. Surfaced with admiration.

• andrewdcampbell/galaxy-sim - real-time browser N-body, Three.js + WebGL, runtime controls and free-orbit camera.
• magwo/fullofstars - the original real-time N-body galaxy toy this project's art direction takes after. Pure JS + WebGL, no build step.
• simbleau/nbody-wasm-sim - 2D N-body, Rust + wgpu, force kernel runs as a WebGPU compute shader.
• MichaelJCole/n-body-wasm-webvr - browser universe in WebVR, physics in a Web Worker, AssemblyScript -> WASM.
• someguynamedmatt/gravity - compact gravity sim on the same Rust + wasm-bindgen toolchain. Bare-surface reference.
• zotho/rust_n_body - Rust N-body with native + WASM builds from one crate. Integrator-focused.
• aestuans/blob - Rust -> WASM showcase, 2D fluid + gravity in one sim, renders WebGL from the WASM side.
• DrA1ex/JS_ParticleSystem - 1M particles in real time. Hierarchical spatial-tree O(N log N) + pluggable CPU/GPGPU backends + record-replay.
• davrempe/webgl-nbody-sim - 3D N-body in vanilla WebGL, no build step.
• holmgr/gemini - sci-fi trading-and-smuggling over a procedurally generated galaxy. Terminal UI over a Rust core.

Contributing

External contributors are welcome. One non-obvious prerequisite: the pre-commit pipeline includes a coily-trailer hook that calls coily, a CLI used to audit and trail commits across this workspace. Install it before your first commit, or the hook will fail.

Deployment

Deployed to galaxy-gen.coilysiren.me. Docker image published to GitHub Container Registry, served through Caddy on k3s on kai-server via Tailscale. See the deploy GitHub Actions workflow for the pipeline.

Commands

Dev commands are declared in .coily/coily.yaml. Run them as coily exec <verb>.

See also

• AGENTS.md - agent-facing operating rules.
• docs/FEATURES.md - inventory of what ships today.
• .coily/coily.yaml - allowlisted commands.

Cross-reference convention from coilysiren/agentic-os#59.