Good game, idea is a bit over used, but I still liked it.
I was really pumped every time I was given a new weapon, but I hated how every time I did the character would not move afterwards. I would always get hit then. If you could fix that, or even just make the new gun appear after the level, would help the flow of the game.
A couple changes could be made,
-Instead of always getting into a car, why not a house or celler (if that does happen later, don't pay attention to this comment)
-Health packs or more damage/upgrades
Everyone says these comments, but just adding these little common attributes can help the games score.
All in all, I liked the game, but could use some add-ons or a change of repition.