I like the concept but i am not sure if i agree with the execution.
I think the view should be bigger for the player as i found it very frustrating when an enemy would pop up in the other side of the screen and not leave me a chance to attack. Also letting the enemies walk over the spikes which take up a good amount of space, leaves no chance for me defend myself unless i go at the very top of the screen which is too risky. I think most of this can be fixed by just increasing the view by a little bit, not even a lot and i think that would really help the game! (just my opinions of course!)
Still, i think it has a solid theme and it is very original! So good job!