[dapalrvk] Checkerboard rotor script

Instead of a star field simulation in the moving alphabet, let it be a pattern of moving light and dark regions.  If we want the feature that all letters are indistinguishable in a snapshot, this will require thought to make similar expansion/contraction versus rotation/translation. Simplest is colored Voronoi regions (neighbors not necessarily different colors) of points that appear or disappear near the center.