Earlier quoted context omitted.
Thanks! Perfect match as far as I can see, nice one! How did you learn/know how to do this? The code was really interesting to read and tinker with! I made a version where the symmetry (7 originally) can be other numbers, and that was fascinating to see! ShaderToy forever!!
Ah silly me, you put the sources in the comment!! Thanks for that I will have a read for sure! It struck me as looking a bit like a demoscene plasma effect but with a radial/angular aspect! (also reminds me of cymatics diagrams a bit!) I experimented with non-integer symmetries and it seemed not to introduce discontinuities, and I made it produce an RGB value for fun too: https://www.shadertoy.com/view/7XsGWs
I doubled the angle so that it doesn't drift to the side any more.. and put it back to 7-symmetry, but left it with the coloring I added (now adjustable via consts):
https://www.shadertoy.com/view/7Xl3Ws
And a small tweak:
https://www.shadertoy.com/view/73lGDs
If you squint with it on fullscreen on that last one there's a wonderful mixture of things feeling like they are rotating vs flowing inward-and-outward from 'centers' (like it's ambiguous whether it's curl or divergence somehow for my eyes/brain at least!).
Hooray for sines and cosines and shaders and thanks for motivating me to play!