I Can Shoot Things!

As of today, the player gun is movable with the Z & X keys, and SPACE fires a missile. The missile collides with the force field bunkers and gradually damages then destroys them, so the collision detection method I'm using is now proven to work. Everything's working really smoothly, so I'm very pleased with the progress so far. 

I also tried putting in some simple PLAY command sound effects to see how it affects the flow of the game. That also worked well so I don't think sound is going to be a problem as I'd anticipated it might be.

Next step is to get the missiles colliding with the aliens and taking them out ..  BOOM!  :D