TGintervals

TGintervals is a mobile interval timer optimized for iPhone. This repository contains the current standalone web release. It has no third-party runtime dependencies.

Files

File	Role
index.html	Markup and meta tags only
styles.css	All styling
app.js	Timer, Web Audio, wake-lock, and screen logic
sounds/	The three MP3 cues (countdown, round-end ding, completion)
icons/	Home Screen and favicon artwork
manifest.webmanifest	Install metadata and portrait preference
service-worker.js	Offline cache of every file above
_headers	Security headers for hosts that honour the file (see below)

All of these must ship together. The service worker lists each one in its app shell, and tests/release.test.js checks that the list is complete.

Use on iPhone

Open the hosted URL once while online. For the app-style experience, offline launching, and the portrait preference, use Share → Add to Home Screen. Portrait is requested by the web app; iPhone Portrait Orientation Lock remains the guaranteed way to prevent rotation in a regular browser tab.

The timer pauses when it leaves the foreground. When you return and tap Play, it rebuilds its Web Audio context so transition cues can recover after another audio app has been used.

Deploy on GitHub Pages

The site is served from the repository root. In the repository settings, under Pages, choose the main branch and the / (root) folder. GitHub Pages serves over HTTPS, which the service worker requires.

GitHub Pages cannot send custom response headers, so it ignores _headers. The Content Security Policy is therefore repeated as a <meta> tag in index.html. Because no script or style is inline, that policy allows only same-origin files. Keep the two copies of the policy in sync when editing either one.

Deploy on Netlify or Cloudflare Pages

Upload the repository folder with index.html at its root. These hosts read _headers and send the security headers themselves, including frame-ancestors, which a <meta> policy cannot express.

Release a new version

Bump the version in package.json and the matching CACHE_VERSION in service-worker.js. The release test fails if they differ. Installed copies pick up the new cache on their next online launch.

Test

Run:

npm test

The test suite uses only Node.js built-in modules. It runs the full workout from setup to completion and checks which cue plays at each boundary, checks the progress sentence, and covers the iOS audio lifecycle, wake-lock races, overdue countdown handling, install assets, the service-worker shell, and the offline fallback.