A very cool and unique concept! Even though the art is simple, it's really polished. Good job since you're just a one-man-army. The UI design might benefit from some more refinement though, it took me a while to figure out how the game works. A tutorial would be nice - then again, you did mention in your game page that the first few runs should be for figuring out the mechanic. You can also tune some movements of the enemies as well I think, making it less likely for the player to be constantly cornered. Perhaps 1 enemy movement per 2 player movements?
This has a lot of potential as a puzzle game for mobile devices to be honest, or a minigame of some sort.