Nice basis for a game.
Things that I believe are great:
* The setting is very unusual and cool.
* It's fun to experiment with the various weapons.
It might require some improvements:
* Enemy shots are difficult to see. Readability is key for this kind of game.
* I would prevent enemy firing from outside of the screen.
* It's very difficult to avoid projectiles, or maybe I misunderstood something. Projectiles are super fast.
Good luck :-)