The shape they chose for the frame is a Möbius strip, which has the primary defining characteristic of having only one side and one edge. If you pick a row of keys to follow, after one loop around, you’ll be on the underside of the frame. Continue to go around another full turn and you’ll be right where you started. So both sides are actually just 1 side that loops around with a half turn of twist. A similar math curiosity would be the klein bottle, which has a single surface.
The shape they chose for the frame is a Möbius strip, which has the primary defining characteristic of having only one side and one edge. If you pick a row of keys to follow, after one loop around, you’ll be on the underside of the frame. Continue to go around another full turn and you’ll be right where you started. So both sides are actually just 1 side that loops around with a half turn of twist. A similar math curiosity would be the klein bottle, which has a single surface.
Adam Savage on Tested nerding out about Möbius strips and klein bottles.