Here is the riddle...
100 Doors in a Row
You have 100 doors in a row that are all initially closed. you make 100 passes by the doors starting with the first door every time. the first time through you visit every door and toggle the door (if the door is closed, you open it, if its open, you close it). the second time you only visit every 2nd door (door #2, #4, #6). the third time, every 3rd door (door #3, #6, #9), etc, until you only visit the 100th door.
question: what state are the doors in after the last pass? which are open which are closed?
I solved this problem with a simple bash script. Then instead of just showing the answer I made it show how it arrived at that answer. It makes what I think of as "Digital Art" and its cool in my opinion.
The video in the following link is a slight variation in that it colors all of the 0's as white and all of the 1's green. (vimeo.com/57641698)