076 lesson, timestamp at 08:02 - a question relating to a negative value for the &__input margin

[hazartilirot]

Hello to everyone!

Could any body explain me how an image i.e. a magnifier icon is able to overlap search form? I can't remember the detail relating to the matter. I can't recall if we used a negative value for a margin. Does it become possible once flex is used? The icon seems to be stuck to a right side of a form. Wow, it's really impressive! I wonder why Jonas didn't make emphasis on the feature.

If so... why does the icon hover over search field (above), not under?

The last question is unrelated to the matter but I'm also curious about the icon's background. What is the purpose in using a color? Can't icon's background be just transparent? I tried.... no difference.