Why Do Mirrors Flip Left and Right But Not Up and Down?

[curious] When you raise your right hand in front of a mirror, your reflection raises its left hand. But when you jump up, your reflection also jumps up—not down. Why do mirrors seem to flip things horizontally but not vertically? The obvious answer feels straightforward: mirrors must have some inherent property that reverses left and right while preserving up and down. Perhaps it's because mirrors are typically taller than they are wide, or because light bounces differently along horizontal versus vertical planes. But this explanation falls apart under scrutiny. There's nothing special about the horizontal dimension in the laws of reflection. Light bounces off a mirror's surface at the same angle it arrives, regardless of direction. The physics simply doesn't support a special "left-right flipping" property. So we have a contradiction: the physics says mirrors shouldn't preferentially flip any direction, yet our experience tells us they flip left and right but not up and down. This is the mirror paradox we need to resolve. Let's take a step back. Imagine writing a word on a transparent sheet of plastic.