You might have played with a Spirograph or other geometric drawing toy when you were a kid. Here you'll find those amazing abstract patterns created from repeating curves and loops--but you'll also find many others that you'd never create with a set of cogwheels and a pencil, where the curves and loops have turned, thanks to computer manipulation, into angles, polygons, and dazzling starbursts. Colorists who enjoy working with symmetrical patterns like mandalas will find designs--from simple to fiendishly detailed--for all tastes, moods,...