As a personal study to understand the basic construction of regular geometric shapes with only a compass and ruler, I found it hard to remember each step. Animating the process seemed like the best way to document for future reference.

A for Astroid Two circles with radii one-quarter and three-quarters the radius of the fixed circle are rolling inside. Points on their circumference both trace this four-cusp curve.

I made a thing! - One point simply rotates around the origin (over the dotted circle). The other four points are attached to the smaller circle centered at the aforementioned point. The smaller circle.