I do not always comment but when I do I have some things to complain about. This game is WAY TOO EASY ! ! (but it's nice anyway) after 5th mission (I replayed 2 or 3 maps ~4 times) you can easily get homing missles. Once you get them there is no challenge in this game. Maps 7-13 you can pass without even moving your mouse or touching your keyboard. Last map is decent fight, but last boss is great dissapointment. After destroing first cannon you can stick to one side of a map and made move only to progress further/change side.
I think that rising prices might help. Now you can skip most weapons/ships (I bought 3 of each of them during whole game)
And pls make last boss move or fire to the sides.
Sorry for my english :) . Game is still fun to play.. but all this I mentioned make it too short. I didn't even tried normal mode, there was no need.
Anyway it's 4 from me and gratz for developer ;)