Cardioid generated by a rolling circle (red) on a circle with the same radius (blue). The same point on the rolling circle paints the curve as it rolls. A cardioid is a single cusp epicycloid. (Project inspired by @juliomulero on Twitter.)
The name "cardioid" was coined by de Castillon in 1741. Named for its heart-like form, it is shaped more like the outline of the cross section of a round apple without the stalk. More information: https://en.wikipedia.org/wiki/Cardioid https://en.wikipedia.org/wiki/Epicycloid
