That's hardly a meaningful rebuttal.

  C = 2 * Pi * r = Tau * r
  A = Pi * r ^2 = Tau / 2 * r

PS: When dealing with radians Tau is fine, but I like showing +Pi and -Pi both point away from 0.

> I like showing +Pi and -Pi both point away from 0.

What would be cool is to see two different points showing what the direction is.

c = Pi/2

+c would point upwards, -c would point downwards. 4c is a pizza.