Half of level 1? As in fo real new improvements?
Just more levels?
Well then, here are my suggestions.
Firstly, even on low quality, it ran low on the uni machine (normally very speedy compared to my 666. Also, you seem to only sometimes fire lasers. This means that when you go around, clicking and destroying things, but not firing anything, you feel a wee bit distant from the action.
Also, you might want to consider limiting your ammo or something, because otherwise, it can become a case of blasting willy nilly at stuff you can't really make out...
Basically, make it so that lasers or something appear each time you fire, along with a wee noise.
Also, consider making it bitmaps instead of vectors, becuase I know shit, but this might be what's slowing it down so much...
Oh, and I might be wrong, but I think that the old Snes RPG was called Drakhen. It was also the name of an old (possibly WW2) aircraft.