Actually, I just want to be able to remember the name of this file. Still, "links" could refer to pairs of pork sausages. These are in no particular order.
Technical paper summarizing the author’s philosophy "Metarealistic rendering of real-time interactive computer animations"
Generally readable paper by Hanson, Munzner, and Francis "Interactive Methods for Visualizable Geometry"
A whole book on the subject, now availabe in paperback, the author’s "A Topological Picturebook"
Wikipedia is OK, but Eric Weisstein’s Wofram MathWorld is much better on mathematical subjects.
Turtle Graphics works in (most) Pythons Here’s some turtle syntax
The classic book on turtel geometry is by Abelson and diSessa. "Turtle geometry: the computer as a medium for exploring mathematics." Cambridge, MA: MIT Press, 1981
Currently, the macs come with a graphing program, not unlike DPGraph, called "Grapher". It replaced a better known, older application, Ron Avitzur’s Graphing Calculator, which has a very colorful story.
Here is a link to an interesting discussion of 2D-RTICA tools, like KSEG and GEX, for constructing figures.
Here is a link an introduction to turle python by its creator, Gregor Lingl, of Vienna. It’s in German if you want to practice. Python f\"ur Kids - das Buch.