An interactive simulation of flat-spacetime relativity — a moving light clock, a live Minkowski diagram, the twin paradox, and the relativistic Doppler effect — built with SceneryStack, Vite 8, TypeScript 6, and Biome 2.
- Light Clock — a light clock at rest beside one gliding past at an adjustable β, with the photon's zigzag drawn and the two tick counts drifting apart by exactly γ
- Spacetime Diagram — drag two events on a Minkowski diagram while a velocity slider shears the primed axes live; light cone, lines of simultaneity, invariant hyperbolas, and a readout that contrasts the invariant interval with the frame-dependent order of events
- Twin Paradox — place the turnaround event and watch both worldlines, both clocks, and the jump in the traveller's "now" that resolves the paradox
- Relativistic Doppler — a source flying past an observer, with wavefronts, the received colour computed from the retarded emission event, the transverse redshift by γ, and forward beaming
- Natural units (c = 1) throughout, so light rays are always at 45°
- English, Spanish, and French localization via
StringManager - Full keyboard access, screen-reader summaries, and default/projector colour profiles
- Progressive Web App (installable, offline-capable)
- 100 unit tests over the pure physics modules, plus a memory-leak suite
npm install
npm run icons # generate PNG icons from public/icons/icon.svg
npm start # dev server → http://localhost:5173| Command | Description |
|---|---|
npm start / npm run dev |
Start Vite dev server |
npm run build |
Type-check + production build → dist/ |
npm run build:single |
Build a single self-contained dist/index.html |
npm run preview |
Preview the production build locally |
npm test |
Run Vitest unit tests (includes memory-leak suite) |
npm run test:fuzz |
Playwright input fuzz smoke (?fuzz, default 15s) |
npm run test:fuzz:quick |
Shorter fuzz smoke (10s) |
npm run check |
TypeScript type check |
npm run lint |
Biome lint check |
npm run format |
Auto-format all files |
npm run fix |
Lint + auto-fix |
npm run icons |
Regenerate PNG icons from public/icons/icon.svg |
npm run clean |
Remove dist/ |
Query parameters: ?initialBeta=0.8, ?showRapidity=true, ?shadeLightCone=true.
New sims start at version: "0.0.0" in package.json. Bump only when cutting a release (for example npm version patch and a matching git tag). Keep name in kebab-case; it is separate from the SceneryStack sim identifier in src/init.ts.
| Tool | Version | Purpose |
|---|---|---|
| SceneryStack | ^3.0.0 | Simulation framework |
| Vite | ^8 | Build tool + dev server |
| TypeScript | ^6 | Type-safe JavaScript |
| Biome | ^2.5 | Linting + formatting |
| vite-plugin-pwa | ^1 | PWA + service worker |
GNU Affero General Public License v3.0 — see OpenPhysics org license.
See OpenPhysics contributing guidelines. Report bugs via GitHub Issues; use org issue templates.