Moiré Hexagons
Paula Beardell Krieg made a nice Moire pattern by outlining a pair of hearts. (See here, http://mathhombre.tumblr.com/post/139240082254/moir%C3%A9-hexagons)
In this sketch you can change the shape and the number of tracings. The second shape travels in a circle around I. You can offset it (s) and have it turn or not as it revolves.
Just for fun!