Darwinity

Upload a lecture, PDF, or YouTube once — Darwinity builds notes, flashcards, quizzes & podcasts from what you were taught.

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Inspiration

Students already have the material — lectures, PDFs, slides, YouTube — but still rewrite it by hand into notes, then again into flashcards, then again into quizzes. Darwinity started from that loop: one upload should become a full study set, not another blank page at midnight.

What it does

Darwinity is a native iOS/Android study app. Upload a lecture recording, PDF, or YouTube link once; the app builds:

  • AI notes from the source you were actually taught from
  • Flashcards for spaced repetition
  • Quizzes to test recall
  • Podcasts for learning on the go
  • Exam prep practice from the same set

Free to start. Pro unlocks higher limits and premium features via in-app subscriptions.

How I built it

  • Client: Expo / React Native (TypeScript), React Navigation, TanStack Query, Zustand
  • Monetization: RevenueCat (react-native-purchases) for Pro monthly/yearly offerings, purchase, restore, and entitlement sync
  • Auth: Apple Sign In + Google Sign In
  • Backend: Darwinity API (notes, quizzes, flashcards, podcasts, billing status)
  • Native extras: local Expo modules for focus shields / study alarm

Public open-source client (MIT): github.com/schandu-eng/darwinity-mobile

RevenueCat

Pro is powered end-to-end by RevenueCat:

  1. Configure SDK with platform API keys
  2. logIn with the Darwinity user id so entitlements follow the account
  3. Load Offerings → monthly / yearly packages
  4. Purchase + Restore Purchases on Account
  5. Listen for CustomerInfo updates and map the Pro entitlement to the paywall / limits UI

Product IDs: darwinity_pro_monthly, darwinity_pro_yearly.

Challenges

  • Keeping store IAP + backend plan status consistent (trial/geo rules vs App Store / Play products)
  • Shipping a real study loop on mobile (upload → notes → flashcards → quiz → podcast) without collapsing into a thin API wrapper
  • Making the paywall honest: free must be useful; Pro is for volume and premium surfaces, not a brick wall on first open

What I learned

Thoughtful monetization is product design: offerings, restore, and entitlement listeners matter as much as the paywall screen. Expo + RevenueCat made cross-platform subscriptions tractable so I could spend time on the study UX.

What's next

Polish the demo path for judges, tighten onboarding, and keep iterating on recall quality from real coursework uploads.

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