SayBetter AI
A voice coach for the conversations that matter — rehearse them before you have them.
LightOn Plus Lab · Anyang, Korea
We build apps, ship them to the stores, and run them ourselves.
A one-person AI app studio that takes a product from idea to store listing to daily operation. Shipping is the start — we keep fixing from user feedback.
10Apps on the stores
3min+Song length Songbit writes
4Languages AI Note hears
2Google Play · App Store
Apps on both stores
Planned, built and shipped here, then kept in repair from user feedback. Eight on Google Play, seven on the App Store — five are on both.
Momoi
Upload a call recording and AI writes the summary, the tasks and the calendar entries. It files; you act.
Upload once: transcript → summary → action items
Speaker-separated transcripts show who said what
Dates mentioned in the call land in your calendar, with reminders
Screenshots and pasted text get sorted into projects and deadlines too
Songbit
Choose a few keywords and AI writes the lyrics, the melody and the vocal — a song that is yours.
Genre, mood, keywords → AI lyrics → finished vocal track
Pick a voice: soft, powerful, husky or rap
Pick a language: Korean, Korean-English mix, or English
Keep, play and share what you make. Free credits when you sign up.
LightOn AI Note
Takes down lectures and meetings accurately, then makes them stick with AI summaries and spaced repetition.
Live transcription, plus speaker separation in precision mode (Korean, English, Chinese, Japanese detected automatically)
Key summaries, an AI tutor, flashcards and quizzes generated for you
Spaced repetition (SRS) decides when you review
Notes are encrypted on the device — no cloud sync, no ads, no tracking
Coupon Book
Paper coupons, stamp cards and passes in one place. No sign-up — it stays on your phone.
Ganada Play
From consonants and vowels to words and sentences, with Hoya the tiger cub. Hangul for small children, by sound and stroke order.
Stone Arena
Gomoku, Alkkagi, Go, Janggi and Chess in one app. Ten computer levels and two-player games.
CORE SIEGE
Wave defense — hold the core against a swarm closing in from every side.
Optical design
Open lens design files in the browser
Open CODE V .seq and Zemax OpticStudio .zmx files as they are and read ray traces, spot diagrams, MTF and aberrations. The file is computed inside your browser and never sent to a server. A lens prescription is the design, so it could not work any other way.
Lens dataSurfaces, radii, thickness, glass and index — read like a prescription sheet.
Aberration and distortionAstigmatic field curves (T and S) next to distortion against f·tanθ and f·θ.
Through-focus MTFResponse by frequency across a focus shift of ±5 to 50 µm.
Zoom positionsSwitch between zoom positions. A sample lens is included to open right away.
How we operate
Exactly what we declare in the Google Play Data Safety section.
Encrypted in transitMomoi, Songbit and AI Note encrypt data in transit.
Deletion on requestYou can ask us to delete your account and data at any time.
AI Note stays on deviceNotes are encrypted on the device. No ads, no behavioural tracking.
Run in the Seoul regionThe backend runs on Google Cloud Run in the Seoul region (asia-northeast3).
What it runs on
What these apps actually run on. Nothing listed that we do not use.
Mobile
App Framework
Flutter · Android
Distribution
Google Play
Web
Frontend
Next.js · React · TypeScript
Hosting
Vercel · Cloudflare
Cloud
Runtime
Cloud Run (Seoul region)
Data & Auth
Firebase · Firestore
AI
Language Models
GPT-4o mini · Gemini 2.5 Flash
Speech
Soniox transcription & diarization
Media
Music
AI music generation engine
Image
Imagen
Payments
App
Google Play Billing
Web
Toss Payments
Other things we run
Besides the store apps we build and run web apps and games. The games open and play with nothing to install.
Bible Search
Search scripture by voice or text, browse by feeling, and follow a reading plan.
Receipt AI
AI OCR that files expenses from one photo — nine categories and a monthly report.
HOLE
A hole that swallows the city and grows. Endless mode and a two-minute rush — plays in the browser.
Noddak
Photograph the ticket and it reads the offence, weighs the appeal and drafts the objection.
Pet Log
Upload a photo and AI keeps the diary in your pet's voice, tagging mood and health signals.
Math Friend
Step-by-step solutions from primary school to the college entrance exam. Photograph a problem and AI explains it.
Notes from building
What we actually ran into while building apps and getting them onto the stores.
Why recording and summarising a lecture still does not make it stick
Transcription and summaries are everywhere now. The paradox is that the tidier the note, the less you go back to it. On the forgetting curve and what spaced repetition fills in.
Why the lyrics drifted up to 16 seconds — match, do not count
Karaoke lyrics drifted further the longer the song ran, and worst in Korean. The culprit was not the timestamps but how we counted words. Replacing proportional estimation with character-offset matching.
Putting a web app on Google Play — a TWA release, in practice
Wrapping a PWA as a TWA and shipping it: the steps and the traps — assetlinks, AAB signing, target API, closed-testing requirements.
Hand it to someone who has shipped one
We build your product the same way. One person carries it from planning through store listing, in-app billing and operation.
01 BriefFrame the problem and the user flow
02 PrototypeProve the core AI feature
03 LaunchShip web and app, wired up
04 ImproveImprove from the data
Fast MVP
A working MVP in two to six weeks, so the hypothesis gets tested early.
AI Ready
Designed by someone who has wired up LLMs, transcription, diarization and generative media firsthand.
Ship
From deployment to store listing and in-app billing — we actually ship it.
Support
Thirty days of free fixes after launch. You get all the source. No lock-in.
Have a project?
An idea, or an AI feature for something already running — either is fine. We reply within 24 hours.