It kind of depends on what you build. Shah Kur is a chess trainer that lets you set novel types of invisibility to help teach you to learn to play blindfold ch

It kind of depends on what you build. Shah Kur is a chess trainer that lets you set novel types of invisibility to help teach you to learn to play blindfold chess (without a board). It's got VAD + voice recognition (can use on your phone hands-free) alongside a WASM implementation of the chess engine, etc. Lend Me Your Ears is a free piano game in the style of the old "Simon" toy which presents players with a sequence of musical notes and challenges them to reproduce the sequence using either an on-screen piano or a connected MIDI keyboard. It uses the Web MIDI API and YIN for realtime accurate detection of notes (so you can use a guitar for example). That's just a few examples, but you'd be surprised how far you can get with nothing more than a client-side application.