Hi, my name is

Ryohei Kameyama

After graduating from university, I founded covelline, LLC in 2013. We are a small team making mobile apps. I am raising my two daughters and developing music composition tools and other experimental software as OSS.

I'm passionate about...

  • 🥽Mixed Reality
  • 📱Mobile Apps
  • 🌐Web technology
  • 🎸Guitar
  • 🤘Progressive Metal



2016 - Present

An open source online MIDI editor. Developed to create a cross-platform MIDI editing environment, powered by WebAudio, WebGL, and WebMIDI. It has a built-in full-scratch SoundFont player, and was built using React and MobX.



A zero-dependency WebAssembly parser and runtime built in pure TypeScript.



A graphic design tool with a built-in code editor. It performs mutual conversion between code and graphics. It automatically converts vector graphic operations by mouse or other means to code, and conversely, reactively reflects code changes to graphics.



A visual programming environment for JavaScript that supports Promise and allows you to compose asynchronous programs in a flow-based programming style.


I spent five years building a web app, posted it on Hacker News, and got my first $1.

This is the story of five years spent wandering around the JavaScript tech stack, wasting time, getting lost, and finally taking off.

サイトを Vercel に移行しました

今まではレンタルサーバーに PHP を置くという古き良きブログスタイルでした。Vercel と Next.js で、コンテンツは全部 GitHub のリポジトリに入れておくスタイルに移行しました。