First off, try writing some instructions; if you toss your players in with no idea what they're supposed to do then you've already lost. Okay, now that that's off my chest, time for the good and bad.
I actually liked the simple graphics, but a larger screen size would have helped, and an option to turn off the (admittedly decent) music is always a plus for me. I also loved the concept of the game; stay away from the enemies long enough for the door to open and then make a break for it. Unfortunately, as several reviewers have already pointed out the game is too short. Adding more levels makes it longer and more memorable.
Overall, this was fun but weak. With some more work it could be great. The idea is a keeper and would make an excellent sequel.