Player ship can shoot!

Getting some really general functionality in around shooting and not letting the player go beyond the bounds of the screen. Trying to decide if I really want to be a stickler for the whole “what an angle means” in the game. Since Y increases in a downward direction, my natural thinking about angles is turned 180 degrees (or PI radians, har har). If I really cared I would make some utilities that took care of it for me.