video of how to turn a sphere outside in

Along the lines of my previous post on 10th Dimension, here's a great brain-bender illustrating how you can turn a sphere inside out (and outside in).

Lots of great instruction on how to think about turn numbers and circles and the effects of corrugation.

(while the video is 21 minutes long, you can see the payoff within the first two minutes and then the "proof" takes the rest of the time).

What's your turn number?