CSS change the style vertical responsive menu

Question

How to change the style, if the menu switch to vertical?!?! Responsive Menu

<ul class="vertical medium-horizontal menu">
  <li><a href="#">Item 1</a></li>
  <li><a href="#">Item 2</a></li>
  <li><a href="#">Item 3</a></li>
</ul>

I tried for example:

.vertical li{background-color: #000000;}

Answer 1

Put the change in the corresponding @media query.

/ From the site you linked /

@media screen and (min-width: 40em) {

li {background-color: #000000;}

}