Why doesn't the bottom style work in css?

Question

css

I make a burger for mobile devices. I wanted to position 3 elements (lines), but the style does not work for the last element bottom: 0;. I checked in the code inspector on the site, stupidly does not work. What's wrong? Tell me, maybe something is wrong in the parent.

Answer 1

You need to cancel the rule with top. top: auto;

.menu-burger-line_third {
    bottom: 0;
    top: auto;
}

Answer 2

Remove top for her, due to the fact that both top and bottom are indicated, she is centered