It's pretty easy.
I LOVE THIS GAME! This should be a classic now. Only problem is that the game is TOO easy. After like level 27 I don't even have to look at my screen. I am actually typing is as the game is progressing, losing very little to no life what so ever. I think you should increase the difficulty of the game. LIke add more life to the soldiers or decrease the insane amount of powerups the player can recieve. Another thing is that annoying sound after killing those cannons...they SUCK! i hate that sound, it kills me to kill them :-D. but overall i love it. thanks for your work.