That pattern reminded me of a physics lab experiment we had to do over 40 years ago -- roll a ball down a slide on the bench and and land it on a piece of of carbon paper on the floor to make marks on a white paper underneath. I think it had something to do with approximating pi, but I forget now. But we were supposed to drop the ball 100 times, but after the first few times, and then chasing the ball across the floor, every time we retrieved the ball, we whacked the paper 5-6 times with the ball in our hand. It sped up the lab, that's for sure. Nice face -- still pristine outside the sweetspot!