COOO.OOO is mainly circles, and I've done a lot of work on circles. My circle-sphere calculator returns the area, circumference, radius, and diameter of a circle. And the volume and surface area of the corresponding sphere. From any starting point. So, if you know the volume of a sphere you can quickly get the surface area or diameter. I built it for myself when I was checking the sizes of viral cores (I did many viral graphics that needed 3D models built to scale). I've also done animations illustrating some mathematical properties of circles and spheres:

Circles are buried in many things, as illustrated in my animations of sine waves, cosine waves, tan waves, and circular polarisation: