Recently I installed free drawing apps on my iPad, Android phone (moto X), and PC, and trying them out just for fun. I find them really convenient because there's no need to clean up afterwords, and there is no preparation beforehand, and anything I don't like I can wipe it off in a whim. No mess, no fuss, and instant gratification.
I mostly experiment to see how much I can make the design interesting by using a simple concept. In this case, this is made with only circles.