say A is a set of concentric circles, each having width B and distance C between consecutive circles. If the background is white, the circles are black. B = C for any given A. The origin is random. The circles continually expand outwardly (spanning the whole screen), generating more circles at the center. Now put several A's on the screen at different origins, different B/C's, and different speeds of expansion. At any given pixel all the overlapping color values are XOR'd with eachother (still yielding only the colors black and white). Alternatively: use spinning spirals instead of expanding concentric cirles, arithmetic spirals, not logarithmic. Also: try having the origins of the circles or spirals moving around the screen randomly according to splines. i've actually made this program, not sure if I still have it.