Hi Taron, thanks !
I though "fireworks" initially, but it is more like optical fibers with visible light on, you're right !
Hi Pilou,
Daniel Shiffman is a great teacher, i bought his books and they are always on my desk. BTW the code from Reas above is actually based on a Particle class initially made by Shiffman.
"why not put a color drawing lines, point, curves anything you want under this ?"Do you mean for instance each "branch" with a given color like in here ?

=> This is not feasible with the program as it is, because the branches are not build one after the other : some pixels are added on one branch, then on another branch (which has its own growth attributes), then a third branch, and so on in a round-robin scheme; at computer speed, that gives the nice illusion that branches grow all together, just like in nature. With my current program, I would need basically to change color for every new pixel added, which is way too time-consuming with the mouse robot above Verve. I'll think of a solution.