Tap the space bar. Wait until the list stops moving. Repeat.
I was experimenting with lists when this happened! What this does is multiply the newest values of X and Y to get the newest value for XY. This is repeated as many times as there are values in XY. When the cycle is over, the variables VX and VY are changed by 1, and then are added to the lists X and Y. Then the cycle repeats.
