Derelict. I used to create lots of experiments with automata, swarms, genetic algorithms, and all manner of virtual creatures that follow simple rules. I lost most of it at some point.
Load an image. Randomly select a pixel, a shape, and the shape's size. Draw with transparency proportional to its size. Decrease the maximum size of the shapes over time. Further create a shape size gradient centered on the picture's point of focus.
particle properties: attractors, repulsors, springs, noise (ate too much sugar)
After a near decadal hiatus, made this small particle sim to show my son (who is now interested in coding) how some very basic rules can create emergent behaviors. E.g. asymmetric rules between attractors and repulsors; repulsors get red when they are near others and push on them, attractors attract them, the effect is they get red (angry) and appear to chase the attractors.
[particle properties and randomly selected, so not all emergent effects are always seen]
an entire hard drive gets physically lost
Following the paths of bugs. Each "bug" has a forward field of vision divided into three sectors. Each bug follows a very simple set of steering (and color choice) rules that use the number of fellows in each sector as input. The visual acuity, speed, and color algorithm of the species is randomly computed before each simulation. Paths are drawn on an AWT VolatileImage.