A personal, ad-free interval timer for Android, built for the gym: one tap starts a saved routine, and the whole screen changes colour with the phase so you can read it from across the room.
- Saved routines, one tap to start. Repeats of work and rest (e.g. 10 × 1 min), a plain timer, or blocks with several phases, warm-up and cool-down.
- Work until done. When you don't know how long a set takes, the timer counts up, you press Done, and a fixed rest counts down before the next set.
- Readable from a distance. Huge digits, the full screen in the phase colour, the next phase and total time left, big pause / skip / stop buttons.
- Its own volume. A timer volume slider separate from media volume, optional ducking of your music while a cue plays, spoken phase names, a 3-2-1 countdown.
- Sound, sound and vibration, or vibration only.
- Survives screen-off. Runs as a foreground service with a notification (pause, resume, skip) and keeps the screen on while running, if you want.
- No confirmation dialogs. Stop and delete happen at once, with a 3-second undo.
- No ads, no accounts, no network.
The app is not on the Play Store. Download the APK from the Releases page, or add https://github.com/bicanjirka/interval-timer to Obtainium to get updates automatically.
Requires Android 15 or newer (minSdk 35); developed and used on a Pixel with Android 17.
Kotlin, Jetpack Compose and Material 3 Expressive. You need JDK 25 and the Android SDK.
./gradlew assembleDebug testDebugUnitTest # build and run the unit tests
./gradlew installDebug # install on a connected device
./gradlew recordRoborazziDebug # render every screen to app/build/screens/*.png
On Windows use ./gradlew.bat.
engine: the pure-Kotlin timer. It computes the current phase and time left from elapsed monotonic time and the routine, never by counting ticks, so pause, resume and late ticks stay exact.service: the foreground service and the cue player (beeps, speech, vibration).data: routines as JSON in DataStore, plus settings.ui: stateless Compose screens; screenshots are rendered on the JVM with Robolectric and Roborazzi.
Design notes and decisions are in CLAUDE.md; open items and the on-phone checklist are in TODO.md.
Pushing a tag such as v1.0.0 runs the tests, builds a signed APK and publishes it as a GitHub Release (see .github/workflows/release.yml).