Really fun, reminds me of being a kid and playing with a Spirograph.
I was just thinking about this little device the other day but the name eluded me. What fanciful amalgam of search terms must one employ to locate such a thing via search engine? Stymying!
Thanks for dropping that gem here.
Seems like this is intended for desktop web use. Which while disappointing from one perspective is refreshing from the perspective that (in general) mobile is for consuming and the desktop can be for creating/producing.
I recommend you to check Sketchbook  from Autodesk for doodling on iOS devices. It’s free. It also has the symmetry feature and I use it quite a lot for doodling. It’s so fun!
 - https://www.sketchbook.com/