I first showed this piece at FOTB 2007, and posted it during the 2007 GalaxyGoo Flash-a-thon.
In this piece, cells are created and positioned on a grid. A cell's position is determined by it's order of creation. But on creation, a cell is randomly assigned an "atomic number". This number then determines additional properties for that cell, such as color and speed.
User interaction is very simple: click on the stage to set up a grid, set elements in motion, and starting over with a new grid.
Click on stage to activate:
first click --> set up grid
second click --> move elements
third click --> clear elements
fourth click --> back to first click state