If two circles happen to collide, there is a flash of white to mark the
position of the collision (unless the collision occurs inside of the
original circular starting pattern, which would create a black collision
marker). The collision forces the circles away from each other. To help facilitate collisions, each circle checks to see if it is near any of the other circles. If the distance separating them is small enough, they become drawn towards each other.
This is beautiful. It's hard to imagine how only the intersections of
circles could build such an organic-looking structure. I am reminded of a biological cell under viral attack.
I like the explosive and powerful beginnings. The composition has a kind of “unity in variety,” which makes it quite compelling – I think it could be interesting to see a juxtaposition of the many variations (say, 100 screen shots) in one big image.