Some time ago I found a website called http://new.weavesilk.com/
It's basically an online interactive art game. You draw art using only your mouse and some very basic presets, but even though your tools are limited, the fun you can have with this isn't. It's a really simply way of making stunning art within minutes.

You can also share your work with other people, who will then be able to watch exactly how you drew everything. Here's something I made really quickly http://new.weavesilk.com/?mxaf

Tips:
-Alternate between the symmetry that you draw with, it can make a big difference.
-Try hold down your mouse button for an extended period of time, sometimes you'll get some really nice stuff out of it.
-If you want to create "eyes", tap your mouse a lot of times. Eventually it'll turn into a circle and somewhat resemble an eye. The time you need to tap depends on how fast your computer processes the game.

Challenge:
-Draw so much on the screen that everything becomes completely white.