The design of the ship is nice and the enemies are kind of cute ^^
I think the enemies are coming a little bit too fast. It's ok when you can see them far from the right, but when they are on top of you, you can barely see them before approaching you.
The core concept is here and I can see the amount of work you did there. You gave it all, and for a first, it is really nice !
I can see that you ran out of time for some things, so I would like to give some advices of what I feel about your game if you want to continue it (or for your next game ;) ). This is not negative criticism, but just ways I thought would improve the game :)
It is a nice idea to have implemented a jetpack animation for your character, but it is a bit small and hard to see in the background. Maybe you took a too big limitation for pixel art size. Or try to do jetpack alone and attach it to the player.
I find the fact that you are shooting only in the directions of your character feels "heavy". Maybe adding mouse control to shoot where you pointe is would have been better. (In that case it is really only my opinion though).
And last, the lack of sound design really gives an impression of emptiness. I do believe that adding just the sound of the gun would have be enough. Or the sound of an alarm running all the time too (which would have been nice with you red alarm going in the game). Don't put too much sound too, or it will be just death for hears x)
But overall, really nice try in the Jam. Congratulaitons for your contribution !