Acid Interval: Focus Timer

Pomodoro timer for deep work

Only for iPhone

Free · In-App Purchases

iPhone

Eight mechanisms, ten colorways, one second at a time. A focus timer worth looking at. Most focus timers look like a spreadsheet with a countdown in it. This one is built the other way round. A single enormous numeral, bleeding off the edge of a field of acid green. Behind it, a mechanism that moves in time with the clock and never drifts. Rings that bounce, breathe, ripple inward, or pass momentum down a Newton's cradle. A square whose perimeter burns like a fuse, four seconds a side, for box breathing. When you start a session the whole field inverts to black and the numbers light up like something switched on behind them. Tap anywhere to start. Swipe to change the color. You never have to open a menu. 25/5, 50/10, 90/20, or count up. The classic pomodoro, longer ultradian blocks, or open-ended flow when you don't want a deadline. Timed properly. Built on timestamps, not ticks. Lock your phone, switch apps, come back: it is exactly where it should be. It tells you when you are done, even with the screen off. No account. No sync. No data leaves your phone. ACID INTERVAL PRO One payment unlocks all eight mechanisms, all ten colorways, and custom interval lengths. The timer itself is free and always will be.

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Box Breathing. A new mechanism: a square whose perimeter burns like a fuse, four seconds a side. Inhale, hold, exhale, hold. The ember parks at the corner through each hold, so stillness on screen is stillness in your lungs. Three new colorways. HER, MECH and TENNIS, each with its own daylight and nighttime palette rather than one color inverted. The mechanism now has a name at the top of the screen, and tapping it cycles through them. Gestures are on screen instead of hidden after first launch, and the controls were regrouped so they are harder to trigger by accident: a tap begins a session, a double tap pauses it, and swipes handle color and theme. Also: the time of day, a tidier header, and Drift has been retired to make room.

The developer, Preston Carr, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .

  • Data Not Collected

    The developer does not collect any data from this app.

    Privacy practices may vary based, for example, on the features you use or your age. Learn More

    The developer has not yet indicated which accessibility features this app supports. Learn More

    Provider
    Preston Carr
    Size
    951.3 KB
    Category
    Productivity
    Compatibility
    Requires iOS 17.0 or later.
    • iPhone
      Requires iOS 17.0 or later.
    Languages
    English
    Age Rating
    4+
    In-App Purchases
    Yes
    Copyright
    © 2026 Preston Carr