IRC-Galleria

You look in a mirror, and let's say you part your hair on the right side. You look in the mirror, and your image has its hair parted on the left side, so the image is left-to-right mixed up.

But it's not top-to-bottom mixed up, because the top of the head of the image is there at the top, and the feet are down at the bottom.

The question is: how does the mirror know to get the left and right mixed up, but not the up and down?

You'll get the better idea of problem if you think of lying down and looking at the mirror, all right, your hair is still on the left side
and now the left and right that was up and down where as the up and down which looked ok was right and left before and mirror somehow figured out what you are going to do when you look at it.

So try to describe in a sort of symmetrical way what a mirror does that it does not look lobsided, it takes left and mixes it with right and does not do same with up and down.