Probability Detective — README

Single-file interactive lesson (age ~12) distinguishing theoretical probability from observed frequency.

Run it

• Open index.html in any modern browser (Chrome 100+, Firefox 100+, Edge 100+, Safari 15+). No build step, no server, no dependencies, no network requests after load.
• To serve locally: python -m http.server 8000 then open http://localhost:8000/ (plain double-click open works identically).

Structure

• index.html — the entire app (HTML + CSS + JS, ~29 KB).
• EDUCATOR_GUIDE.md, TEST_REPORT.md, LICENSE — required package docs.
• Randomness: seeded mulberry32 PRNG in JS. Every experiment run derives its seed from the visible Seed input + cumulative trial count, so runs are reproducible: same seed + same sequence of actions ⇒ same numbers. Automated tests (below) inject fixed seeds for deterministic verification.

Commands

• Development: none needed (static file).
• Production preview: serve the folder over any static HTTPS host (GitHub Pages, Netlify free tier, python -m http.server). No paid hosting required.

Automated tests

node tests.js (Node 16+) runs deterministic checks of every acceptance example — see TEST_REPORT.md for actual results.

Known limitations

• No audio (optional feature intentionally omitted; handled gracefully).
• Progress is in-memory only; a page refresh resets the lesson (by design — "reset/replay without reload" is provided in-app).
• Charts are lightweight CSS bars; screen-reader users get equivalent live-region text summaries.

Licence

MIT (see LICENSE). All content original; no third-party assets.