AnuPing – Korean Speaking

Practice Korean by broadcasting voice letters into space! An AI announcer-teacher coaches your pronunciation, and every sentence you speak becomes a signal someone out there can hear.

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🏆 Grand Prize, Korean Language Education category — Forbes Korea “First Trusted Premium Brands” (award ceremony: November 2, 2026)

Inspiration

Most people learning Korean can read far more than they can say. Speaking needs a listener, and a live partner is intimidating when you are a beginner. We wanted speaking practice that feels like making something, not like taking a test.

What it does

AnuPing turns Korean speaking practice into a small cosmic radio station.

  • Speak, then broadcast. Every sentence you record becomes a voice letter beamed into space. Letters travel asynchronously, so you never need a matching partner online at the same time.
  • Anussaem, your AI announcer-teacher. An announcer-persona AI scores pronunciation, intonation and pace sentence by sentence and hands you the next line to try.
  • Listeners and contact. Other learners tune in to your frequency. When two stations subscribe to each other, a 1:1 channel opens.
  • Daily rituals. Role-play scenes (cafe, classroom, job interview), a voice diary of spoken affirmations, a daily line from the stars, and a garden where your Anu tree grows golden tangerines you can gift.
  • Your planet is in the real sky. Each station is placed beside a real star in one of the 88 IAU constellations.
  • 11 interface languages, from English and Vietnamese to Nepali and Burmese.

Star Pass (powered by RevenueCat)

The core loop is free. Star Pass ($5.99/month in the US, 2-week free trial) unlocks:

  • Anussaem's premium Earth Classroom lessons
  • An official station license and an unlimited battery for broadcasts and dials
  • Your own vocab book of expressions collected from broadcasts
  • Replay of every voice diary entry (free keeps the last 3 days)
  • Detailed pronunciation coaching, Planet Studio customization, sending again without waiting for a reply, and unlimited role-play (free stops at 7 turns)

How we built it

  • App: Flutter for iOS and Android from one codebase, Riverpod for state.
  • Payments: RevenueCat purchases_flutter. The app fetches the current offering and buys the $rc_monthly package, so pricing and packaging are managed in RevenueCat rather than hard-coded. Each RevenueCat customer is identified by our own user ID and logged out on sign-out, so revenue and customer history line up with our accounts.
  • Entitlement safety: after RevenueCat completes a purchase, the app sends the store-signed transaction (StoreKit 2 JWS on iOS, the Play purchase token on Android) to our server, which verifies it and grants Star Pass idempotently. If that hand-off fails, the app silently re-syncs the next time it opens.
  • Pronunciation engine: our own scoring service (NestJS API with Python workers orchestrated by Temporal) measures each sentence against broadcast-announcer reference speech, and a deterministic fuzzy-logic layer turns the scores into plain-language coaching.
  • Backend: NestJS, PostgreSQL with Prisma, Firebase Cloud Messaging, Docker.

Challenges we ran into

  • Moving an app that was about to launch with native billing onto RevenueCat without losing our server-side receipt verification or store-notification handling.
  • One Apple ID or Google account can hold a subscription that is already linked to a different AnuPing account. We had to make that case explain itself inside the paywall instead of failing silently.
  • Writing honest free-trial disclosures in 11 languages that satisfy both App Store and Google Play review.

Accomplishments that we're proud of

  • A full purchase flow (paywall, RevenueCat purchase, server verification, entitlement, welcome screen) that works on both stores.
  • A speaking app where beginners actually talk, because the first listener is a patient AI teacher.
  • AnuPing has been selected for the Grand Prize in the Korean Language Education category of - - Forbes Korea’s “First Trusted Premium Brands” awards (고객신뢰도 1위 프리미엄 브랜드), with the ceremony scheduled for November 2, 2026. Being recognized by an established media outlet shortly after launch shows that learners see real value in our speaking-first approach to learning Korean.

What we learned

Keep the paywall close to the moment of need. Locked lessons, a full vocab book and older diary entries all open the same Star Pass sheet, so the value is obvious when the price appears.

What's next

  • Test an annual plan and trial length with RevenueCat Experiments.
  • Referral rewards between stations.
  • More Earth Classroom lessons and role-play scenes.

Launch & Community

AnuPing is a social speaking app, so we are launching it where people meet in person. On October 3 we are hosting the AnuPing launch party in Seoul together with DocenTour, for Korean learners and locals. 60 people had signed up as of September 27.

  • Scan, sign up, get Star Pass. Guests install AnuPing from a QR code at the entrance, and everyone who signs up that night gets 3 months of Star Pass (granted by our admin tool alongside RevenueCat subscriptions).
  • Frequency Bingo. Each square asks guests to find someone (from another country, speaks 3+ languages, sent their first broadcast today) and mutually subscribe in the app. The offline icebreaker ends as real 1:1 channels inside AnuPing.
  • Frequency name tags. Every guest wears their station name and frequency (MHz), so finding each other in the app takes seconds.

Event page: https://docentour.app/events/2

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