I'm familiar with Fourier series, and I had a lot of fun with this puzzle! I can see how it might make a nice little game, great job :)
I think most of my feedback is around the controls (I used a mouse) - it's a little unclear what those two knobs down the bottom of the screen are for until you successfully pass a level, or want to reset your shape.
As for the controls on the left, was the intention that they remain unclear to provide the player a little bit of exploration? I'm not against them, but perhaps some further visual indicator to describe which arm it belongs to?
All in all, I can see this as a nice small mobile game, or something. Congratulations on the effort!