Mobile App

Arc Timer

HIIT timer application covering the full workout lifecycle.

Personal-use project evolved into a production-level application. It covers the full workout flow from setup to execution and tracking.

GitHubDocs

App Interface

Key Features

  • Custom workout creation

    Create workouts by defining exercises, intervals and durations.

  • Simple session controls

    Pause, resume, skip or end a session with minimal interaction during workouts.

  • Session history

    Track completed workouts and review past sessions.

  • Workout import and export

    Share and reuse workouts through file import and export.

  • Multi-language support

    Available in multiple languages for broader accessibility.

Implementation Details

  • State-based timer flow

    Workout phases run through a state machine, keeping transitions and session controls predictable.

  • 1Hz engine cycle

    Second-level precision was sufficient for workouts, so the timer runs at 1Hz to reduce overhead.

  • Reanimated UI-thread animations

    Animations run on the UI thread using Reanimated, avoiding load on the JavaScript thread.

  • File-based workout sharing

    Workouts serialize to files for import, export and reuse across devices.

Tech Stack

  • React Native
  • Expo Router
  • React Reanimated
  • TypeScript