Because you are confusing relative and cardinal axes of direction. If you stand in front of a mirror and point up, your image points up. If you point left, your

Because you are confusing relative and cardinal axes of direction. If you stand in front of a mirror and point up, your image points up. If you point left, your image points right. However, up is relative to the surface of the earth, and left is relative to you. If you were to point left as well as east, your image would point east too - now you are considering direction along a common two dimensional set of axes, relative to the earth. The real brainfuck occurs when you point toward or away from the mirror, because now your image points north when you point south, and vice versa - however, other comments here have a much better explanation for that than I can muster.