The game looks nice, I like the seamless transition from the title screen to the actual game. The sea and islands setting is also very nice. The clouds dissolving with shots and hiding hearts is a great mechanic, I just feel they should move at a different speed from the enemies.
I don't know if it's a bug or on purpose, but the ship doesn't move diagonally, or very infrequently. I also felt the enemies were too spongy. I wouldn't mind having to take much more per wave if I could mow them down more easily !