Cool ! The movement and mechanics are nice. It's fun to play.
I think this could work "Asteroids style" too, where anytime the ship goes off screen, it re-appears from the other side, like an infinite canvas. If you haven't rated it yet, try "Momentum Command" it's pretty similar to your yours.
I'm very sorry to have to say this, but....
I wish "k was shot." :)
This totally subjective, but using my other hand to fire feels more natural. Or just provide multiple key bindings and let people choose.
Great job.