Hi, I'm Hangyul

I like not knowing how yet.

Every project here started as something I didn't know how to build. That's the part I enjoy - picking up a new tool, getting stuck, and coming out the other side able to do one more thing.

Projects

start here, these are my favorites

Each one was a new stack at the time.

Igloo Classroom, teacher view of a class with join code, assignments, and roster

Igloo Classroom

AI · Product

A classroom app with a built-in AI assistant. Teachers make classes and post assignments; students join with a code and hand work in. The assistant (Claude) keeps everyone's tasks and calendar, say "quiz Friday at 3" and it's scheduled, and reads uploaded PDFs to pull out due dates and to-dos. Installable as an app, with push reminders and email verification.

Shows: the most I've taken on at once: accounts and roles, streaming AI with tool use, file uploads, email, push notifications. And it's live with real students.

  • Node
  • Express
  • Claude API
  • Web Push
  • PWA
  • Railway

sign up as a student with class code 24CJNH, demo accounts are cleaned up automatically

Shinobi AI Sandbox battle screen

Shinobi AI Sandbox

Game · AI

Turn-based Naruto battle simulator with 48 characters, status effects, clones, and AI opponents that each fight with a different personality: aggressive, defensive, supportive.

Shows: picking up TypeScript and React from scratch, then going deep: a full turn engine and a scoring-based AI, not a tutorial app.

  • React 19
  • TypeScript
  • Vite
  • Tailwind
Igloo Study tester and admin dashboard

Igloo Study

Product · Full-stack

Test-taking platform for a tutoring service I run. Students take level tests in the browser; an admin side handles uploading tests, editing questions, and reviewing submissions. Live, with real students on it.

Shows: keeping something running for real users. When it breaks, I'm the one who fixes it.

  • Node
  • Express
  • PostgreSQL
  • Cloudinary
Coup Online room screen

Coup Online

Multiplayer · Realtime

Online multiplayer Coup with 4-letter room codes. Bluffing, challenges, blocks, refresh-safe rejoin, an optional Inquisitor expansion and a turn timer so nobody stalls the game.

Shows: first time with real-time networking. Learned Socket.IO and server-authoritative state by building it.

  • Node
  • Express
  • Socket.IO
One Device Mafia game screen

One Device Mafia

Game · UX

Mafia for a group with one phone. No accounts, no install. Pass the phone for role reveal, then it narrates the night and day phases.

Shows: caring about the player, not just the code. The whole design problem is one phone that can't leak secrets.

  • JavaScript
  • Vite
more on my GitHub commits, READMEs, the messy parts

Games - Unity → WebGL, playable in the browser

About

I started with Unity in 2022 because I wanted to make something I could actually play. Since then I've kept picking projects a step past what I knew, sockets, a real database, TypeScript, an AI assistant, because the stretch is where I learn the most, and I'd rather keep growing than get comfortable.

The part I'm proud of isn't that these got started; it's that they got finished. Most of them broke badly at some point: a multiplayer game that desynced, a platform that went down with real students on it, and the only reason they work now is that I stayed with the problem until it was solved. I don't mind being stuck. I mind giving up.

Skills

Frontend

  • TypeScript
  • React
  • Vite
  • Tailwind CSS
  • HTML / CSS / JS

Backend

  • Node.js
  • Express
  • Socket.IO
  • PostgreSQL
  • REST APIs

Games

  • Unity / C#
  • Turn-based engines
  • Game AI
  • WebGL builds

Tools

  • Git / GitHub
  • GitHub Pages
  • Render
  • Cloudinary

Contact

Email is fastest. Happy to talk about any of these, or something you're working on.