not just up side down, also backwards p d.

Depends on which way you upside down it. If you rotate it about the x-axis it upside downs to a b, if you rotate it about the y-axis (in three space representation the y-axis is coming out of the screen, what you would normally think of as the y-axis has been relabeled the z-axis while you weren't looking) *then it comes out as a p.

AnnaS and I were puzzling over this bit of ambiguity when Will Shortz stated his weekly Sunday Weekend Edition puzzle a week ago with the hyphenated eight letter word that turned into another hyphenated eight letter word when you turned two of the letters over.

The answer was ping-pong => ding-dong.