I don't know if you're still trying to fix the lag, but for me it's interesting to note that the graphics aren't part of it, the graphics play fine, without any problem, they don't lag, and the game continues going on during the "lag", but what happens (for me) is that the game stops taking input, so like I'll hit the left key (a) for one second, and then walk left for like twenty seconds... I think the one guy's suggestion that it has to do with mouse presses is right, if you could change the fire button from a mouse button to a keyboard button it might fix it, that way it wouldn't risk losing focus or whatever's going on. Maybe not even change it, just make it so F fires the weapons as well as the left mouse button? It might fix the whole problem (maybe?)
You might try remaking this game as a offline game, flash doesn't seem to work well with it. I'm not sure where exactly this lag is coming from in all, but one problem I'm having is with clicking off of the screen (which is often a problem in flash games on Kongregate) which removes the focus and causes the game's performance to jitter a tiny bit, but more importantly stops all input until the focus is regained, so... yeah.
it feels like the game needs more 'polish' to the interface, keeping my fingers on qaz at the same time for one thing isn't very easy. But also like the game feels kindof weird, like it's not done or something... Have you experimented with adding more lives and seeing what that does?
the death animation-thing is rather long, it'd be nice if you just instantly went back to the beginning of the level. You could have the animation play at the spot that you died while you are alive and well at the beginning.
It'd be nice if there was an arrow or some sign explaining where the creeps come from and where they are headed. Not knowing this kindof just made me guess and loose. Grarerr
clicking next level to get to the next level was non obvious to me, for awhile I was just waiting for it to take me to the next level I shot way more ragdolls then I needed to
Having to switch between the keyboard and mouse to deal with the menu is annoying. The length of the animations (the snow loading screens, and the part where the penguin walks away from the day sign) are annoying. I'm probably in a bad mood right now so it's bothering me more then it should, but, fixing those would be nice. It's also difficult to accomplish anything at first, and even later on the distance of the slight doesn't seem very great, it seems like I'm just supposed to keep playing and essentially faiiling and getting tiny amounts of money until it happens to become enough (finaly) to get a single upgrade (even with which it's nearly impossible to accomplish anything).
It would be nicer if the game were faster paced, the slowness is killing me.
The gameplay is not very smooth, and my mouse keeps loosing focus on the game window, but if it were smoother and not buggy I could see it being pretty cool. Good idea.
 "Spy 2"){kind=icon}
 "Tyrant"){kind=icon}
 "Vital Bloodshed"){kind=icon}
 "Zabaax Game"){kind=icon}
 "Multitask Race"){kind=icon}
 "Rebuild"){kind=icon}
 "Quietus"){kind=icon}
 "mini Tower Defence (mTD)"){kind=icon}
 "RagDoll Cannon"){kind=icon}
 "Learn to Fly"){kind=icon}
 "Platform Combat"){kind=icon}