first few levels were hard, but as you get on, they become FAR easier.....i did the last level in 10 seconds.... 4/5 due to it being too easy, but good game
i thought the end was a trick, just sat there for 5mins still holding down right arrow....then my bro came in, saying wtf u doin? lol! i have no life :)
easy, last stage easiest? get all upgrades, all your conrtol turrets, and defend with bombers and keep air control with fighters, and then save 10k then send in 4 warships and own em, when flagship comes, spam fighters and bombers