Every spot on the picture is a number. Left and right change one part of the number. Up and down change the other.
Start with 0. Multiply it by itself, then add your spot's number. Take the answer and do it again. Keep going.
Sometimes it stays small and keeps wandering around. Sometimes it grows bigger and bigger until it zooms off and never comes back.
Spots that stay home are black. Spots that run away get a lighter shade the faster they leave.
Now zoom in on the edge. It never gets simple. You find new shapes, and some of them look like the whole picture again, as far as you want to go.