When a Doom player fires a weapon, the center of the weapon sprite is actually a few pixels to the right of the line of fire (center of the screen, which is also the center of the status bar face). This discrepancy is not normally relevant, because it produces only a small targeting error at short to medium ranges, and because ordinary "bobbing" displaces the weapon sprite by a much larger amount. When aiming carefully at long range, however, the bug becomes apparent.