Lua — Private Period Tracker

A period tracker that runs entirely in your browser. No accounts, no servers, no ads, no tracking. Your data stays on your device.

Try it now | Privacy Policy | Deployment Guide

Why Lua?

Every popular period tracker (Flo, Clue, Ovia) stores your intimate health data on company servers. After the 2022 US Supreme Court decision on reproductive rights, that data became a legal liability.

Lua takes a different approach: it physically cannot leak your data because it never has it. All data lives in your browser's IndexedDB. The optional Google Drive backup goes to your account — Lua has no server to breach.

The name comes from the Portuguese/Spanish word for "moon."

Features

• Cycle predictions — weighted moving average with confidence levels, 12 months forward
• Phase awareness — menstrual, follicular, ovulation, luteal, premenstrual
• Fertility window and ovulation estimates
• Monthly calendar with color-coded period, predicted, fertile, and ovulation days
• Scrolling calendar with tap-to-edit period dates
• Year view — 12 mini-calendars at a glance
• Cycle history — dot-bar visualization grouped by year
• Cycle dynamics chart — SVG line chart of cycle length trends
• Statistics — average cycle length, fluctuation range, previous cycle/period duration
• Import/Export — JSON backup/restore with validation
• Google Drive sync — optional cloud backup to your own Drive
• Offline-first — full functionality without internet (service worker caches all assets)
• Installable — works as a native-like app on iOS and Android
• Bilingual — Russian and English, auto-detected from browser

Privacy

• All data stored locally in IndexedDB
• No analytics, no telemetry, no ads
• No accounts, no email, no phone number
• Google Drive backup is optional and goes to your personal Drive
• Strict Content Security Policy
• Full Privacy Policy

Medical disclaimer: Lua is not a medical device. Predictions are informational estimates based on your past data. Do not use them for contraception or medical decisions without consulting a healthcare provider.

Quick Start

npm install
npm run dev

Open http://localhost:5173 in your browser.

Commands

npm run dev          # Start dev server
npm run build        # Production build (TypeScript + Vite)
npm test             # Run 88 tests
npm run test:watch   # Watch mode
npm run preview      # Preview production build

Tech Stack

Technology	Why
React 19	Stable, TypeScript-first. Client-only — no Next.js/Remix needed.
TypeScript 5.9 (strict)	Compile-time safety from day one.
Vite 7	Fast dev server, optimal production builds, native PWA plugin.
Zustand 5	Minimal state management. Atomic selectors prevent re-renders.
Dexie.js 4	Clean IndexedDB API with transactions and type safety.
date-fns 4	Tree-shakeable. Only imports what's used.
vite-plugin-pwa	Workbox service worker for offline support.

No Tailwind. No Bootstrap. No MUI. All CSS is hand-crafted with CSS custom properties following the Arutyunov Interface Design System.

Browser Support

Works in all modern browsers:

Browser	Install as PWA
Chrome (desktop + Android)	Yes
Safari (iOS 17+ / macOS)	Yes (Share > Add to Home Screen)
Firefox (desktop + Android)	Limited PWA support
Edge (desktop)	Yes
Samsung Internet	Yes

Project Structure

src/
  components/     # React components (calendar, history, settings, etc.)
  services/       # Business logic (predictions, import/export, sync, calendar sets)
  stores/         # Zustand stores (periods, sync state)
  i18n/           # Translations (ru, en)
  styles/         # Single CSS file with design system
  data/           # Synthetic demo data for testing
  test/           # 88 tests (Vitest + Testing Library + fake-indexeddb)
public/
  manifest.json   # PWA manifest
  privacy.html    # Standalone privacy policy
docs/
  ABOUT.md        # Full project story and design principles
  DEPLOY.md       # Deployment guide (GitHub Pages + VPS)

Deployment

GitHub Pages

npm run build
npx gh-pages -d dist

Self-Hosting

See DEPLOY.md for full VPS setup with nginx, SSL, and custom domains.

Architecture Highlights

• Store-level derived state — predictions, cycles, date sets computed once per data load, not per render
• Atomic Zustand selectors — components subscribe to individual fields to prevent cascade re-renders
• Load deduplication — concurrent IndexedDB reads are collapsed into a single promise
• Atomic import — clear + bulkAdd wrapped in a Dexie transaction
• Error boundary — prevents white-screen crashes from corrupted data
• 14-day ongoing period cap — prevents unbounded date expansion in calendar views

License

MIT