This is a quick test of a loop that makes the LEDs "dance".
This means that it will show a random "screen" and show it for some time and repeat.

Two problems with it so far:
  * it looks like 6,7,10 are consistently randomized to "off" every first time
    (meaning that it looks like it is not so "random")
  * it is blocking. it should work like a little FSM that checks for new patterns to do.