This seems a bit incomplete but I like what you have going here. The turn based nature of the game add a sort of tactical decision making to the usual fast paced action of space shooter games. Having to collect ammo rather that starting with it is an interesting twist too. It just needs to restart when you die, have a proper victory screen, and a few more levels and you've got a pretty nice game.
I'm not sure what console you were trying to emulate but it's a bit high resolution for most stuff I can think of. That said, the graphics do look really nice. They have a sort of simple charm to them - I particularly like the look of the alien ships. The black and white colour scheme is also a good choice.