So many enemies, so much space.  Don't let them touch you!  Tilt to control your SpaceBird, your lovely plane.  Fire at them...stop talking...INCOMING!!!

Initial plans and calculations included firing bullets from the direction the FireBird is facing.  Eventually this proved too complicated to play with.  So we stick to firing from the front only.  Well, the math is noted here for future use.
Coordinate System of the bullet