Hey there, Sartoris.
I've played your game and I must say, this game has a lot of potential but at the same time, there is room for improvements.
Music is enjoyable and relaxing, it's a really nice touch. Graphics are cute and simple, but there are couple of things to perhaps think about:
1) Background perhaps could be a little less bright/colorful, so the planes and objects would stand out better. I found myself difficult to navigate and see who is where and what.
2) Clouds are a little strange. Whilst the look cood, they represented to us (players) as if we are looking at them from the side, not top. Also. They seem to move slowly in direction the player moves, but slower than the player. Those are damn speedy clouds :P I believe they should go down from top to bottom like enemies do, to gives us a better impression that we are flying.
Other than that, I would like to agree with Gullberger. Tutorial would be a nice thing to have. It also wouldnt hurt to have a difficulty increase over time. Instead, you're drowning by the enemies straight away :)
With that being said, keep working on the game! It has good potential.