Good overall beginning. Could use some detail work on the textures and your prims have overlapped in some places. Throw some AI peeps running around and some collision effects on lazers and we're good to go :)
I am assuming that I am supposed to be playing against a friend who is also at the same computer? Not sure but I don't think I should be able to choose actions for both sides. Not much time maybe you could add in some upgrades of some sort or something to add some depth to the game. It doesn't seem like much coding at all went into this. Almost like a homework assignment for a class to teach certain aspects of code an not a whole encompassing game.
Excellent story line. Had not yet played the previous games but references to them in the NPC's make me want to go check it out! Great job over all and I can't wait for the next one!