The "impossibility" proof actually uses 3 assumptions: 1. A, D, E, B lie in one plane 2. B, E, F, C lie in one plane 3. A, D, F, C lie in one plane Any of t

The "impossibility" proof actually uses 3 assumptions: 1. A, D, E, B lie in one plane 2. B, E, F, C lie in one plane 3. A, D, F, C lie in one plane Any of these assumptions can be wrong. It's easy to perceive that number 3 is not flat, if you think that 1 and 2 are flat.