Rhythm — MVP rhythm-learning app for drummers

Expo React Native (TypeScript), Firebase Auth + Firestore, web-first. Simple metronome with deterministic timing via the Web Audio API.

Setup

1. Install dependencies

   cd rhythm-app && npm install

2. Firebase

   • Create a project at Firebase Console.
   • Enable Authentication → Anonymous (for “Continue as guest”) and Email/Password (for sign-in and sign-up).
   • Create a Firestore database (test mode is fine for MVP).
   • Project settings → General → Your apps → Add web app → copy the config.

3. Environment (no secrets in code)

   • Copy .env.example to .env in the project root.
   • Fill in each EXPO_PUBLIC_FIREBASE_* in .env with values from Firebase Console → Project settings → Your apps → Web app config.
   • Do not commit .env.

4. Run (web)

   npm run web

   Open the URL in the browser. Use Start on the Practice tab (first tap resumes the audio context).

Project layout

• app/ — Expo Router screens: index, (tabs)/home, (tabs)/practice.
• contexts/AuthContext.tsx — useAuth() (user, loading); signs in anonymously on app load.
• lib/firebase.ts — Firebase init (Auth + Firestore). Config from env; see file comment for where to add values.
• lib/metronome.ts — Timing logic: Web Audio scheduling and visual beat callbacks (see comments in file).
• lib/userProgress.ts — Firestore read/write for last BPM (one doc per user).

Timing (tradeoffs)

• Audio: Beats are scheduled at exact AudioContext.currentTime values in a small lookahead window; no setInterval/setTimeout for playback, so no drift.
• Visual: A requestAnimationFrame loop reads the same scheduler state and updates the beat indicator; one-frame latency is acceptable for MVP.
• Platform: Metronome is web-only in this MVP (Web Audio API). Native would need expo-av or a native module and a different timing approach.

Constraints applied

• Simple, readable code; no heavy abstractions.
• Deterministic timing where possible (audio clock on web).
• No premature optimization.
• No class-heavy design; hooks and plain functions.
• Timing logic commented in lib/metronome.ts.