Early version of a game I'm working on

This is a very early version of a game I'm thinking of developing further, but I'm not really sure what direction I want to go with it yet. It's fairly straight forward right now- fly around, shoot the mobs, score as many kills as you can before you get killed.

http://www.flynn1179.net/games/?page=starpatrol

Right now, I'm just looking for a bit of feedback on the 'feel'- how easy is it to play/control, and how easy is it to understand what's going on, that sort of thing. Not sure if I'm going to just add in more mobs types and probably some power-ups, or go into a more detailed 'mission' style gameplay, with things like rescue missions/boss fights, that sort of thing. Any opinions on direction would also be welcome. The name's a working title, I haven't really come up with a better one yet.