Needs to have a button to swap weapons, since the mouse is used for aiming, it's possible to accidentally move the mouse off the game screen and then when you scroll it scrolls the actual page and messes up your vision on the game.
Also, is there a button to reload? The info on the rifle I have says that I have 30 rounds and a reserve of 90, but no apparent way to reload once the 30 are used up.
Other than that, a lot of fun. I've always enjoyed top down shooters, and this one is done pretty well. Would give 4/5, but dropped half a star for simple but impactful interface issues that I've already discussed.