As you start drawing, your lines are replicated to generate cool pieces of art. Adjust the number of segments, colors, shapes, and line widths to create your own one of a kind rangoli, mandala, or spirograph.
I saw this post on /r/whoadude about an app called Amaziograph and was impressed as someone threw together a javascript version within a few hours. Easily tempted, I spent a few nights coming up with an android version. Since it's release, I've been amazed by the fantastic works of art created.