heh, this level looks just like zipper, and you fail it for the same reason: just because there's an easy way through it, you don't have to continue with it the whole time
It seems like a simple level to the experienced psycho, but some noobs are stumped by its trick. Some have found it so hard that they have started a thread on the forums for it. Minefield has distinction as the hardest puzzle with no moving parts.
This level teaches the most fundamental concept in psychopathian puzzles: Every move you make away from the exit, you must correct with another move towards the exit.