GiantChrono

A fully local, offline-first Progressive Web App showing a stopwatch and a clock with giant digits, readable from a distance (poolside, climbing gym, stadium). No ads, no accounts, no data collection.

GiantChrono reimplements the feature set of Giant Stopwatch by Alexander Pruss / Omega Centauri as a web app, and adds 12 h / 24 h clock format support.

Features

• Giant stopwatch — start/pause/resume/reset, laps with cumulative and split times, digits auto-sized to fill the screen
• Delayed start — configurable countdown with audio "3… 2… 1…" cues (generated locally with the Web Audio API)
• Giant clock — local time, optional seconds, 12 h / 24 h format (automatic from your locale by default)
• Themes — digit color, background color, font, relative size, letter spacing, stopwatch precision
• Gestures & commands — vertical swipe (or button) to switch stopwatch/clock, tap-on-display as a configurable command, keyboard shortcuts (Space, L, R, F, arrows)
• Full screen — ⛶ button or F key to hide the browser chrome (where the browser supports it)
• Lock mode — ignore accidental touches (splash-proof); hold for one second to unlock
• Multiple stopwatches — optional independent stopwatches
• Screen wake lock — keeps the display on while timing (where supported)
• Persistence — settings and stopwatch state survive reloads; a running stopwatch stays exact because elapsed time derives from timestamps, not tick counting
• Offline PWA — installable, works with no network at all, updates in place

Quick start

Requires Bun ≥ 1.2.

bun install
bun run dev        # dev server with hot reload
bun test           # unit tests (timing logic, formats, persistence)
bun run build      # production build into dist/
bun run preview    # serve dist/ locally

The production dist/ folder is a plain static artifact deployable on any file host, at a domain root or a subdirectory (asset URLs are scope-relative).

Documentation

See docs/ for the feature guide, architecture notes, and development workflow.

Privacy

All data stays on your device (localStorage). The app performs no network requests for tracking, analytics, or advertising — the only network use is fetching its own static files.

Author

Sébastien Celles

License

MIT — © Sébastien Celles.

This project was developed with AI assistance.