Actually I found that the animation showed a clear example demonstrating that pi is wrong. I don't know about you, but when I looked at it I immediately recognized the blue arrow and the centre of the wheel. That's a radius. There's no easy way to determine that a diameter was in the picture. As it rolls over the circumference, it's the radius line we follow. Therefore, I agree that pi is truly the wrong constant to show here. And it is wrong in a greater sense than what is presented at tauday. It's actually downright confusing or even misleading to highlight a radius and a circumference, and then talk about pi.