Your mirror image is opposite between left and right. Why your feet and your head are not opposite as well?

Mirrors do not reverse left and right or up and down. Look at yourself in a mirror: your left is on the same side in the mirror as it is on you. What mirrors do is reverse front and back - you and your mirror image are looking in exactly opposite directions!

The mirror just reflects. The reason you perceive right and left as flipped is that you see your image and imagine that you are looking at a person who is turned 180 degrees and looking back at you. But the mirror doesn't flip 180 degrees. It just flips z (front and back) without flipping x or y. So the parity gets messed up. You put out your right hand and it looks to you like image's left hand, because you are imagining a 180 degree rotation, which would flip z and x, but that's not what actually happened, because only z got flipped.

The simple answer would be that our images on the mirror will only be laterally inverted. This means that our left looks like our right and our right looks like our left. This can be explained using diagrams of light rays. We are subjects that cannot produce light. Hence, for others to see us light rays must be reflected from our body (since light cannot pass through any opaque object) into their eyes. When we look at ourselves on the mirror light rays are reflected from our bodies onto the mirror and back into our eyes. Hence, the image that we see on the mirror is laterally inverted but not vertically inverted as there is nothing that can cause us to see our images in the wrong way.

The mirror doesn't "flip" your image, just turn your head sideways and you can see that you don't "flip" from top to bottom. All a mirror does is reflect a light ray directly back. If you imagine lines of light coming off of your body and then reflect them back off the mirror you can visualize why you appear to have your left and right changed.

your eyes are on a horizontal line to each other so the image on flips horizontally