A five for now...
Well, it is a tech demo and it shows some promise. Would like to see more. However, there are some issues to address.
Walking outside of map. A complete no-no.
I somehow stumbled upon this reload sound glitch, where for any step I took, it had the reload sound repeatedly play (similar to holding the R button). I can't replicate the glitch, other than the fact I know I held R down, I was near the turret. Reloading the demo seems to have solved it, and I would figure that you'd solve it normally anyway. Just letting you know.
Player can get stuck on ship and possibly the turret. (possibly, because that hasn't happened to me yet, but I was stuck on the ship for sure). This may happen on other solid objects as well.
Icon on top right screen doesn't change when you switch weapons. (Dunno what you have planned with it; maybe it's just there to show what weapons you have on hand, in which case, you'd have to put a second gun icon underneath that one as well.)
Otherwise, the graphics are good enough, the controls work fine (can't know about reload yet, since you haven't implemented the ammo functions yet ).