Featherline

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HRT tracker for Android: dose log, PK projection, lab results. Encrypted, offline.

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# Featherline

**English** · [简体中文](README.zh-CN.md)

HRT medication tracker for Android with PK projections and lab tracking. On-device, encrypted, no account required.

[![License: GPL v3](https://img.shields.io/badge/License-GPLv3-blue.svg)](https://raw.githubusercontent.com/mkx173/Featherline/main/LICENSE)
[![Build](https://github.com/mkx173/Featherline/actions/workflows/android-release.yml/badge.svg)](https://github.com/mkx173/Featherline/actions/workflows/android-release.yml)
![minSdk](https://img.shields.io/badge/minSdk-26-blue.svg)
![targetSdk](https://img.shields.io/badge/targetSdk-37-blue.svg)

Featherline logs doses across injection, patch, gel, oral, and sublingual routes; projects estradiol levels from your dose history using a three-compartment pharmacokinetic model; and tracks blood test results with automatic unit conversion across canonical and clinical units. Everything stays in an encrypted local database — no accounts, no telemetry, no network calls. Backups are encrypted and compressed. Available in English and Simplified Chinese.

> ⚠️ **Not medical advice.** Featherline is a tracking tool, not a medical device, and using it does not establish a clinician relationship. The pharmacokinetic projection is a rough population-average estimate from your logged doses — it is not a substitute for blood tests or for a clinician's interpretation, and you should not use it to make dosing changes. See [docs/safety.md](docs/safety.md) for the full disclaimer.

## Get the app

- **Play Store**: [Link](https://play.google.com/store/apps/details?id=com.mkx.hrttracker)
- **F-Droid**: [Link](https://f-droid.org/packages/com.mkx.hrttracker)
- **GitHub Releases** (signed APK for sideload): [releases page](https://github.com/mkx173/Featherline/releases)
- Or build from source: see [docs/building.md](docs/building.md)

> **Note:** The Play Store or F-Droid version is recommended. The app holds no internet permission, so the GitHub APK cannot check for updates — you will need to monitor the releases page manually for new versions.

## Features

- Log doses across injection, patch, gel, oral, and sublingual routes
- Configurable reminder schedules with snooze and exact-alarm handling
- Group medications and apply schedules to grouped doses
- Optional medicine stock tracking with low-stock warnings and schedule-aware "days remaining" estimates
- Estradiol pharmacokinetic projection from your dose history
- Blood test catalog with automatic unit conversion (pg/mL ↔ pmol/L, ng/dL ↔ nmol/L)
- Encrypted, compressed backup format with restore validation
- App lock with biometric unlock
- Home-screen quick-log widget in two sizes, with progress, next-dose, and tap-to-log
- Journal tab to track meaningful dates on a timeline with milestones, plus per-day notes; pin any date to your home screen as an anchor widget or shortcut showing its running day count
- No accounts, no telemetry, no network calls — everything stays on device
- English and Simplified Chinese
- Material 3 with dynamic color

## Screenshots

<table>
  <tr>
    <td width="25%"><img src=".github/screenshots/home.png" alt="Home screen"></td>
    <td width="25%"><img src=".github/screenshots/plan.png" alt="Plan view"></td>
    <td width="25%"><img src=".github/screenshots/history.png" alt="History log"></td>
    <td width="25%"><img src=".github/screenshots/calibration.png" alt="Calibration screen"></td>
  </tr>
  <tr>
    <td align="center">Home</td>
    <td align="center">Plan</td>
    <td align="center">History</td>
    <td align="center">Calibration</td>
  </tr>
</table>

## How it works

Featherline is a single-module Android app written in Kotlin with Jetpack Compose. Doses, reminders, and lab results live in a SQLCipher-encrypted Room database. The pharmacokinetic engine is a three-compartment model that converts every logged dose into an estradiol contribution over time, then sums contributions across all routes to produce a projected curve. Reminders use AlarmManager with exact-alarm permission handling and snooze support; notifications survive reboots and time changes through a reconciliation layer. The blood test catalog defines analytes with bidirectional unit conversion via a canonical factor table. Backups are encrypted, compressed, and use a versioned format with full restore validation.

The full architecture, data model, and reminder pipeline are documented in [docs/architecture.md](docs/architecture.md).

## Roadmap

- Replace the pharmacokinetic engine with a more general multi-medication model
- Personal-PK calibration tuned from your own lab results
- Optional encrypted cloud backup (off by default, end-to-end encrypted)
- Additional languages — translation contributions welcomed on [Hosted Weblate](https://hosted.weblate.org/projects/featherline/) (see [docs/localization.md](docs/localization.md))

## Tech stack

Kotlin, Jetpack Compose with Material 3, Hilt for dependency injection, Room with SQLCipher for encrypted persistence, Coroutines + Flow. See [gradle/libs.versions.toml](gradle/libs.versions.toml) for exact versions.

## Building from source

Prerequisites: JDK 17, a recent Android Studio, and an Android SDK whose API level matches the project's `compileSdk`. Standard Android Studio import; run `./gradlew assembleDebug` or use the IDE.

Detailed instructions, flavors, and CI behavior: see [docs/building.md](docs/building.md).

## Contributing

Contributions are welcome. Read the [Code of Conduct](CODE_OF_CONDUCT.md) first, then see [CONTRIBUTING.md](CONTRIBUTING.md) for development workflow, branching conventions, and how to propose changes.

Translation contributions are welcome on [Hosted Weblate](https://hosted.weblate.org/projects/featherline/).

## Privacy

Featherline stores everything on your device in an encrypted database. There are no accounts, no telemetry, and no network calls. See [docs/privacy.md](docs/privacy.md) for the full data-handling description.

## License

Featherline is released under the GNU General Public License, version 3.0. See [LICENSE](LICENSE) for the full text.
Third-party dependency, asset, and adapted-code notices are listed in [docs/third-party-notices.md](docs/third-party-notices.md).

## Acknowledgments

- The [Material Symbols](https://fonts.google.com/icons) icon set.
- The pharmacokinetic projection draws on the math reference from [HRT-Recorder-PKcomponent-Test](https://github.com/LaoZhong-Mihari/HRT-Recorder-PKcomponent-Test).
- The estradiol undecylate pharmacokinetic parameters come from [Transmtf-HRT-Tracker](https://github.com/TransmtfTeam/Transmtf-HRT-Tracker).
- Plot display logic was adapted from [Oyama's HRT Tracker](https://github.com/SmirnovaOyama/Oyama-s-HRT-Tracker).
- The broader trans health community for testing, feedback, and the prior art that makes a tool like this possible.

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