Fun fact: by just using imaginary numbers, some Evil Math, and 101 rotating vectors You Can Create a shitty approximation of a fish.
Alrighty since people are curious:
link to desmos graph. I did not include an explanation for how any of it works. good luck.
link to video explaining Fourier series. Lots of people have already added this which is cool and great. This was my first introduction to Fourier series and it’s extremely helpful and informative.