[sharing | gen] warped circle

inspired by this (still can't figure out proper html tags, see attached image):

I decided to see if I could recreate this in [gen]. I can't figure out one part however, and that is when I hit the warp curve's bounds either below 0 or above 1, i need to perform some mirror/fold/modulo on it so it can seamlessly cross the bounds, but everything i've tried gives me strange behavior. Perhaps someone knows what's up? And once i figure that out, then I can proceed to add multiple warpings.