Emergence and Generative Art
A simple algorithm results in unpredictable and complex patterns when iterated multiple times.
Circles are generated - initially randomly, then within the overlap of the previous generation of circles - over multiple generations. The results are within a solution space - so you have some idea of what they will tend to look like - but still inherently unpredictable, and often unexpected.
The essence of generative art is that you only set up rules, and let them interplay to give you something you could not have predicted.