Not bad.
Addictive game... when the helicopters actually feel like flying by. I have been having two problems: airships that drop their bombs only when they are exiting the screen and the fact that my tank went through 330 units of fuel without anything flying by. Seriously. I thought the game was just trying to piss me off or something, but a reload solved that. Other than that, this game is like crack with a lower street value. Addictive and lethal.