Paula Abdul once sang a poignant song, with an animated dog, about the perils of taking two steps forward, and then two steps back. One Step Back is that sentiment manifest, in game form, and it's awesome.
It's tough to explain One Step Back, you must go from one door to another, but only after a designated amount of time. The issue with this is that the door you entered from is contantly spawning new versions of you following the exact same path that you, yourself, have already taken!
Sounds easy, but it's quite tricky in practice...
One Step Back [Armor Games]