FitBMI — BMI Calculator & AI Health Coach

A modern, privacy-first health app built with React Native & Expo. BMI calculator · AI health coach · live step / water / sleep tracking · gamification · 6 themes · 7 languages — all offline, no account, your data stays on your device.

Live landing page · Privacy · Publishing guide · Contributing

⚕️ This app is for general fitness and wellness purposes only and does not provide medical advice. AI responses are informational only.

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✨ Features

• BMI Calculator — metric/imperial, animated gauge, color-coded categories, healthy range, recommendation cards, confetti for a healthy result.
• AI Health Coach — streaming chat (markdown, typing, avatars, history) plus meal-plan, workout, recipe, goal-planner and weekly-report generators.
• Daily AI Insights on the home screen.
• Health Tracker — live step tracking (device pedometer), weight, body fat, water, sleep, calories; progress rings + weekly/monthly charts.
• Gamification — XP, levels, coins, streaks, reward wheel, daily challenges, achievements, confetti.
• Onboarding that collects your profile on first launch.
• Design — glassmorphism, Light/Dark/AMOLED + 6 theme variants, Poppins + Inter, reduced-motion aware, 60fps animations.
• i18n — 7 languages (en, es, fr, de, ar, hi, bn).
• Local-first — AsyncStorage; no backend, no account; CSV/report export.

🧱 Tech Stack

React Native 0.81 · Expo SDK 54 · React 19 · TypeScript (strict) · Expo Router · NativeWind · Reanimated 4 · Moti · Zustand · React Query · React Hook Form · AsyncStorage · react-native-svg (charts) · @gorhom/bottom-sheet · i18next · expo-sensors · OpenRouter (AI) · Lucide icons · Google Fonts.

Runs in Expo Go (SDK 54) — storage uses AsyncStorage and charts use SVG, both bundled in Expo Go, so no custom dev client is required.

🚀 Quick Start

git clone https://github.com/devSahinur/FitBMI.git
cd FitBMI
npm install --legacy-peer-deps

# (optional) enable AI features
cp .env.example .env        # add EXPO_PUBLIC_OPENROUTER_API_KEY

npm start                   # scan the QR with Expo Go, or press a / i / w

--legacy-peer-deps is needed because a few RN libraries declare strict React peer ranges (a project .npmrc sets this automatically for CI/EAS).

AI setup (optional)

AI features use OpenRouter with automatic fallback across free models first (DeepSeek, Llama 3.3, Gemini Flash, Qwen) then low-cost paid ones. Add a key to .env:

EXPO_PUBLIC_OPENROUTER_API_KEY=sk-or-...   # from https://openrouter.ai/keys

Without a key, AI screens degrade gracefully and the rest works fully.

📁 Project Structure

src/
  app/         Expo Router routes — (tabs), ai/, auth/, onboarding, premium, …
  components/  Reusable UI — ui/, ai/, auth/, charts/, gamification/, layout/
  screens/     Screen implementations
  features/    ai/ (prompts, types), food-scanner/, community/, bmi/
  hooks/       useTheme, useChat, useStepTracking, useReducedMotion, …
  store/       Zustand stores (persisted via AsyncStorage)
  services/    storage, openrouter, ai, pedometer, notifications, export, …
  i18n/        i18next + 7 locales
  theme/       colors, typography, spacing, shadows, variants
  utils/       bmi, units, format, date, stats, csv, xp
docs/          Landing page + hosted Privacy/Terms (GitHub Pages)
store/         Play Store assets (icon, feature graphic, screenshots)
e2e/           Detox scaffold

📜 Scripts

Command	Description
npm start	Expo dev server
npm test	Jest unit tests
npm run typecheck	TypeScript (no emit)
npm run lint / format	ESLint / Prettier

🧪 Testing

Jest unit tests (44) cover BMI math, unit conversions, date/streak helpers, CSV, XP/levels, AI prompt builders, OpenRouter model-fallback (with expo/fetch mocked), and the history + gamification stores. AsyncStorage is mocked. A Detox e2e scaffold lives in e2e/ (needs a native build).

npm test

🗺️ Roadmap

Some modules are built but intentionally disabled, ready to enable:

• Re-enable the History tab
• Community (leaderboard, friends, challenges) — features/community
• AI Food Scanner (camera + barcode) — features/food-scanner
• Real in-app purchases (premium architecture is ready)
• Background / Health Connect step tracking (dev build)
• Full per-screen i18n string coverage

🤝 Contributing

PRs welcome! Please read CONTRIBUTING.md and make sure npm run typecheck, npm test and npm run lint pass.

📦 Publishing

See PUBLISHING.md for the full Google Play build & submit guide, Data Safety mapping, and ready-to-paste store listing copy.

📄 License

MIT © 2026 Sahinur · infosahinur@gmail.com

Built with React Native & Expo. Icons by Lucide, fonts by Google Fonts, AI via OpenRouter. Use only free, commercially-licensed assets when contributing.