Rounds

A loud, clear interval timer. Pick a preset (Tabata, 4 × 4, EMOM, 30/30, HIIT 40/20, boxing rounds, core) or make your own: warm-up, work, rest, rounds, sets with a break between them, cool-down, and optional exercise names.

• Three short beeps, one per second, count you into every work round, then a long high "go" beep; three more count you out of it, then a long low "stop" beep. Beeps are scheduled on the audio clock, so they stay on time.
• Full-screen colour for each phase, a big countdown inside a ring dial, spoken cues and vibration (optional).
• Optional live heart rate: tap ♥ beside the dial to connect any Bluetooth strap or watch that shares the standard heart rate signal (Polar, Garmin HRM-Dual/Pro, Wahoo TICKR, Coospo and most others). The finish screen shows your average and peak heart rate in the work rounds. Needs Web Bluetooth: Chrome or Chromium on Android or desktop, or Bluefy on iPhone and iPad; elsewhere the button simply doesn't appear. Readings are shown only, never saved or sent.
• Free and open source. No account, no ads, no tracking. Timers are stored on your device and never sent anywhere; the web app only fetches newer copies of its own files, and works offline once added to the home screen.

Android app

Download the APK from the latest release. The install guide explains how to install it, check that it's the official build (SHA-256 checksum and signing-certificate fingerprint) and keep it up to date, for example with Obtainium. It isn't on Google Play: we support Keep Android Open. How it's built, and how to build and sign your own: mobile/README.md.

Manual and support

The user manual is at https://anonacondacodelab.com/rounds/manual/ (source: docs/MANUAL.md). Questions or problems: [email protected]. Security issues: see SECURITY.md. Changes are listed in CHANGELOG.md.

Development

Plain HTML, CSS and JavaScript. engine.js holds the timer logic and hr.js the heart-rate connection; both are tested with npm test. node build.mjs copies the app's own files into dist/, which is what the website publishes (Cloudflare Pages runs the build; _headers holds the HTTP headers) and what the Android app in mobile/ is made from.

© 2026 Anonaconda Code Lab. GNU General Public License v3.0 or later (see LICENSE). Fonts: Instrument Sans and IBM Plex Mono, SIL Open Font License; the Android app's components (MIT and Apache-2.0) are listed in NOTICE.md.