Having fun with Hypotrochoids

Hypo what??
Hypotrochoids.
Maybe you know it from when you were a little kid and you played with a SpiroGraph set.
I got this somewhat more 'grown-up' art set. Basically the same as the SpiroGraph, but the tools are a bit more sturdy and professional, it came in a pretty box and it's called by the official geometric name Hypotrochoid.
Decorated these small cards which will be send out to some lovely creative people very soon.