repetitive, not much challenge
After about 15 enemies, they start repeating in exactly the same order doing exactly the same things. All you have to do to survive is remember a few actions. The only particularly tricky enemy to avoid is the one with the laser eyeball that sweeps the room. To get past him you have to get down behind him before he starts shooting and crouch. By the way--I'm not sure it makes a difference, but if you jump and start crouching _before_ you hit the ground, you will crouch lower ("inside" the ground) so that only your head shows.
It's an OK game but the enemies need to be randomized and do different things.