https://books.physics.oregonstate.edu/GMM/book.html

The Largest Collection of Interactive Geometric Puzzles

120 Levels: From Very Easy to Really Hard, 11 Tutorials, 10 Innovative Tools, Automatic Verification of Solutions, “Explore” Mode and Hints, Dynamic Geometry in Action

This article explores the mathematical and geometric relationships between musical intervals, scales (like the Chromatic Circle and Circle of Fifths), and esoteric concepts such as the Pythagorean Tetractys.