At first glance the monicker “spirograph” seems wrong, because where are the gears? However, [Yoshihito] has them stashed underneath the sheet of paper, with magnets controlling the pens.

[Tuchman] starts with a quick proof-of-concept using an actual plastic Spirograph toy to make sure ... but he needed to adjust gear ratios and ergonomics to make the device more usable.

Spirograph, a geometric drawing device, creates mathematical roulette curves known technically as hypotrochoids and epitrochoids. In simpler terms, it's a toy that uses gears to produce intricate ...