I have to say, this game really is beautifully crafted. The controls are smooth, and propelling through space to different planets is very fun. More instruction would be nice. The puzzles aren't very obviouse.
Here's my question- If choppers are so strong, why do they cost less than the airship? I massed heavy tanks on lv 4 and got the truck to reach the hostage, then massed airships. I had the same amount of airships as they had choppers, and i focus fired on each one individually, but they still killed me and took out the truck.