Really cool and very irritating since movement is basically reversed but then you also control everything else in the level but controlling the enemies is even weirder (yes, I read that you control the whole level, but this is how it felt to me).
Maybe it would feel more like moving the level if you decided to put the player in a fixed spot (e.g. center of the screen) and move everything else around it.
With everything considered it was still a very enjoyable experience - music and visuals also helped a lot :)