not too good there =P
a few points i would like to make:
-the reloading system was kinda hard to fiddle with i didn't even know where it was
but there should be a hotkey to it.
-like someone else said, there should be more guns and more "non gun" upgrades.
-the graphics were abit small and overall not very easy to see things.
-the enemy's were too small.
if you could touch up on those points it would be alot better =P