I spent some time profiling and optimising my code again today, with some really great improvements, making continued development much smoother.
I brought in another key feature used throughout the series - the flow lines. There's multiple ways the starting points are selected and the length can vary quite a lot. I've also added the possibility of sub-dividing the small circles into groups so that they are treated differently.
I'm already getting a lot of interesting variation in the output, which is making it harder to choose one for the day - a nice problem to have. I've selected this one in part because it showcases some of the new possible features.