When we started FretsNotes, it was an iOS-only app. The engine, the UI, the curriculum — all built for iPhone. But we always planned to go cross-platform, and this week we shipped the Android version to Google Play.

Same Engine, New Platform

The core of FretsNotes is a Rust engine called NotesKit. It handles everything: exercise generation, mastery-weighted scheduling, adaptive difficulty, the hint system, curriculum parsing. When we decided to build for Android, we didn’t rewrite any of that. Instead, we used Mozilla’s UniFFI to bridge the Rust code directly into Kotlin.

The result: every exercise on Android behaves identically to iOS. Same prompts, same mastery tracking, same adaptive logic. The engine doesn’t care what platform it’s running on.

Built with Jetpack Compose

The Android UI is built entirely in Jetpack Compose — no legacy XML layouts. Navigation, theming, state management, and all 16 exercise mode views are Compose-native. We used Hilt for dependency injection and DataStore for local preferences.

Authentication uses Google’s Credential Manager for native Google Sign-In. Your account syncs across both platforms through our Phoenix/Elixir backend.

The Full Curriculum

All 110+ courses across eight series are available on Android from day one. The curriculum loads from the server with offline caching, so you can practice without a network connection after the initial sync.

What This Means for You

If you’ve been waiting for Android support, it’s here. The app is currently in beta on Google Play. Request early access and we’ll get you set up.

And if you’re already on iOS, your progress syncs. Pick up your Android tablet and keep going right where you left off.