Draw a closed outline and one of these solves the eigenvalue problem for that exact shape and plays what it would really sound like. Another puts a trout somewhere in a simulated current and tells you why your guess was wrong.
Eigendrum via Web Curios
Draw a shape, hear the sound it would actually make
→ baselashraf81.github.io
A browser trainer for reading a trout river
→ read-the-water.netlify.app
A browser game about the unwritten rules of train seating
→ welidev.github.io