Decent!
I played this around twice and couldn't beat it in 25 days, but it was pretty fun. The graphics are neat in how everything is a cardboard/paper cutout, and the humor is cool as well. There are minor flaws though that affect gameplay, and I'm taking 3 points off for these as they easily could have been fixed.
1. Lag.
This is actually really simple and easy to fix. Since the game has quite a few things offscreen, I suggest putting code on things that are no longer in view to stop animating completely. I have done this several times as a quick fix for my platformer and it works as a charm.
Assuming you are using AS2... you could probably adapt it for AS3 if need be:
if(this.hitTest(_root.vcam)){
this.play();
} else {
this.stop();
}
I don't know if your game works like that, but it would work in some sort of variation. Another thing you could do is cut animation down a notch, maybe skip on a filter or two, etc.
2. Replay value.
Many of these games go for a long time, but this game in particular has very little replay value besides medals. There were not enough upgrades in general and the locale was the same the entire time. You could turn it into Infectionater more, where you could travel the world and do this, maybe, let's say, 80 days? Yeah. I do however appreciate the work that is in it already, and I must say, this is a very solid game in general.
3. Reactions.
Sometimes it felt (yes, I know, ironic) as if nothing was really taking place in the game. I would shoot objects and there wouldn't be a sense of reaction from them. Blood or jolting from people when you shot them would have been nice, and maybe cars could have done flips in the air when they exploded, and debris could explode into pieces everywhere, causing even more chaos.
Just some ideas for a sequel.... which I desperately want to play.
But overall, this is a pretty decent game and I hope maybe some day we can collaborate!