As a school kid (14? 15?), I won a prize to go to Birmingham University (UK) each Saturday morning for a term, to do a maths course. The teachers took turns in taking me and another to the course. One of the things I remember doing was playing with all kinds of geometrical transformations of triangles (e.g. bisect each of the edges to get the circumcentre and then add a circle which had that centre. As you adjusted the shape of the triangle everything updated in real time). It was running on what must have been a mainframe. This was my first (and only?) experience of using a mainframe. I remember being rather unimpressed with the mainframe, since it hung and crashed once. The interface was also a bit crap. As all of the students started doing this work, the mainframe started to struggle and slow down! These libraries look to be able to do similar stuff which is very cool.

I had fond memories of that, and was a reason I got into Computer Science and Maths. I wanted to recreate it, but I've never really tried to do it. These libs look like they could be just the thing.