My mother plays badminton almost every day at our apartment complex club and frequently enters municipal and regional tournaments. Whenever she competes, she always records match videos. But the video files were too large to send over messengers, so she asked me for help several times. Once, a match was so long that I had to downgrade the resolution and split it into three separate clips just to send it. She finds cloud platforms like Google Drive unintuitive and difficult to use. So I built this to solve the problem for her—and definitely not because I got tired of her asking me!

A web service for sharing large files

React, Next.js, Firebase

My younger brother is a high school senior this year. He has always struggled with English. I took three attempts at college entrance exams myself, and after the June mock exam of my repeat year, I never once missed a Grade 1 in English. From my perspective, vocabulary is 90% of mastering English. My brother did not seem particularly eager to study, but rather than nagging or coercing him with harsh words, I wanted to use my skills to genuinely help his studies. That is why I created this app.

Free CSAT English vocabulary study service

React Native, Expo, Firebase

My brother loves playing this retro game, but found repetitive grinding tedious. So I decided to build this both to help him and to study AI hands-on. Using a YOLO model, the system recognizes monsters and characters, assesses the situation, and executes skill and movement actions via Python code.

This is a video of the very first runnable version. I extracted map data, monster info, and sprites from MapleStory WZ files compatible with MapleLand and MaplePlanet, synthesized monsters onto background maps to create 50,000 training images, and left my computer running for two weeks to train 50 epochs per continent—until my 10-year-old desktop broke down. In the end, my brother could not play the game anymore either. A happy ending. Bots like this should never be used anyway.

I happened to learn about Vitamin C mega-dosing. All my life, I caught colds whenever seasons changed, and often had an upset stomach even when eating the exact same meal as my family at home. So I started mega-dosing. Naturally, that led me to research other supplements. There were dozens of different types, and sorting through them gave me such a headache that I decided to build this service.

A service where AI recommends optimal supplements based on your answers to simple questions

React, Next.js, React Native, Expo, Firebase

Originally, I intended to build a global tournament rock-paper-scissors game. Rather than real-time synchronous play, users would enter a tournament bracket, make their choice (Rock, Paper, or Scissors) once matched, and winners would advance through rounds to earn rewards. However, my primary work got so busy that development stalled, and as time passed, it became harder to pick up again. Fearing I might never ship it, I scaled it down to core rock-paper-scissors matches and released it. I plan to revamp it into the full tournament format once I have more bandwidth.

A rock-paper-scissors game with people worldwide

React Native, Expo, Firebase

I play morning weekend football occasionally, and noticed the team manager always struggling and complaining about how tedious it was to draw up lineups every week. So I built this formation builder for him. He loves it and uses it regularly.

React, Next.js, Firebase

While we should let go of past setbacks, when something you have poured your heart into does not work out, you easily fall into tunnel vision and self-blame. One day, seeing a push notification from the Toss finance app, a thought struck me: Why do notifications only convey practical information—why not emotional comfort? That inspiration led to this app.

A service where AI sends comforting and uplifting messages at scheduled times

React Native, Expo, Firebase

I rewatched Attack on Titan. My brother had never seen it, so I introduced it to him and watched a few episodes together—and ended up binge-watching the entire anime again. Truly the greatest masterpiece of my life.

Watching it suddenly sparked a desire to learn Japanese. I have an aunt and uncle living in Japan, and wonderful memories from traveling there with friends. All those fond memories seemed to come together.

Free Japanese study app for beginners

React Native, Expo, Firebase

At the time of making this, I had an argument with my girlfriend. We had not officially reconciled, but were not actively arguing either—caught in that awkward silence. I thought this would be a fun icebreaker to break the tension. I also made a few playful mosaic messages to tease my brother. It might seem trivial, but it was genuinely delightful to build and share.

A service that sends photos and messages hidden inside interactive mosaics

React, Next.js, Firebase