Martin Krzywinski's π Day 2014 art. The digits of π are folded like a protein: prime digits (2, 3, 5, 7) are treated as sticky, and the path curls to pack them next to each other. The energy counts how many sticky pairs touch — the more, the tighter the fold. He used replica-exchange Monte Carlo; so do we, live in your browser. Bend it onto a circle for Planet π. The second mode draws each group of digits as a stacked rainbow ring.