Great game... a few issues
Graphics, good. Music, good.
Issues:
1) If you hit multiple buttons (A, S, D, F) at the same time, you get a weird zoom.
2) On certain levels where the enemies keep spawning, when you shoot them, they disappear. They should at least fall down and fade out, if you want, but having them disappear isn't so hot.
3) Not being able to shoot enemies just because they're kneeling down is pretty lame. Make it so the spots that they run to have cover, so when they duck you can't see them at all, or something.
4) On the gift shop board (level 10, I think?) I killed about 5 people, then people stopped coming. It wasn't locked up, but the level wouldn't end and no one else was coming. Having a level reset button would fix this, I think.
I didn't have the problems others had with completing the levels, just the afore mentioned items. Overall, really good game with a few annoying problems. Keep it up!
PS... I'm running IE v7.