I pwn boats
Alright buddy, lots of suggestions for you:
-larger game area/range
-make weapons buyable. I don't like waiting for them and I had plenty of extra cash.
-Change the upgrade system. I didn't buy upgrades because I knew it would only be waster money after I got the next weapon.
-add some sort of story - why are all of those ships attacking a turret in the middle of the ocean?
-more upgradeable things like health regeneration, machine gun ammo capacity, splash size.
-mines would be a good tertiary weapon.
-for the machine gun, one gun would be better than two because it's a pain to hit those little guys.
-I would like to see the cooldown for the cannon and the ammo for the machine gun on the left side of the screen.
And that's it for now. What you have is good though. Have fun.