fireAtXY(x, y) → {Phaser.Bullet}
 Fires a bullet at the given coordinates. The bullet will be launched from the Weapon.fireFrom position,or from a Tracked Sprite or Pointer, if you have one set. 
Parameters
Name Type Argument Description x  number   <optional> The x coordinate, in world space, to fire the bullet towards. y  number   <optional> The y coordinate, in world space, to fire the bullet towards. 
Returns
  Phaser.Bullet -   The fired bullet if successful, null otherwise.