Show HN: PianoFun – Browser piano learning game with MIDI (vanilla JavaScript)

My daughter is learning piano, and I saw someone on X who vibe-coded a similar app for their kid. So I plugged a USB cable into our 10-year-old Casio AP-450, fired up Claude Code, and had a working falling-note game in minutes.

My daughter immediately became the product manager — she requested a beat toggle, caught that long notes disappeared too fast on keypress, and spotted visual overlaps I completely missed.

Deliberately vanilla JS/HTML/CSS — no frameworks, no build step. Setup is: USB cable + Chrome + open index.html.

Open source (GPL-3.0): https://github.com/victorantos/PianoFun