Super cool stuff. For anyone wanting an explanation of what’s going on, a Fourier series is a way of representing a complex shape as a sum of cyclic sine equations. These sine equations are shown visually by OP as a series of blue line segments in the center. Each individual line segment is rotating at a constant speed throughout the ‘drawing’, and the combination of all the segments draws the track. Fourier series off the top of my head are often used in anything dealing with many frequencies packed into one signal, such as analysis of vibrations or radio signals.