> I still find pic really useful ...  > I don't know of any other tool
that lets you do drawings like that

Unix had "ideal", a remarkable language by Chris Van Wyk, based on complex
numbers and capable of some constraint solving. Its code seemed to be
lost but can now be found in one of the online v10 repositories. I've
been meaning to try to resurrect it. If anyone has already done so,
I'd love to hear about it.

I, too, have some pic macros, though no big coherent packages, to do
things like  polar coordinates and solving for the intersection of lines
and circles. I have even in extremis made filled triangles with scripts
that massage PostScript by deleting corners of filled rectangles. Then
from triangles you can, with patience, make polygons.

Doug