Nice game. I particularly liked the general aesthetic, style of the UI, and the starry background. The feedback is nice as well, with the camera shaking when you get hit, and the sparks and sound effect when you hit an enemy.
I couldn't tell at first that the symbols in the upper left corner were for shields and health and that shields regenerated, but I figured it out eventually.
I found myself wishing for strafing controls at first. If you can only shoot in the same direction you can move, it's very difficult to avoid damage. I figured out a way to minimize damage by boosting around more and taking advantage of the tiny amount of inertia. I think letting the player maintain more inertia would make the game more engaging, though the enemies' aim would probably have to be improved in turn.
The aim up/down controls didn't feel useful without a reticle.