Menu bar hover effect.

[Motofumi Suzuki]

Which CSS file I need to edit in order to change the menu bar hover effect? 

I'm thinking to put something like a code below. 

a {
  position: relative;
  display: inline-block;
  text-decoration: none;
}
a::after {
  position: absolute;
  bottom: 2px;
  left: 0;
  content: '';
  width: 100%;
  height: 2px;
  background: #333;
  opacity: 0;
  visibility: hidden;
  transition: .3s;
}
a:hover::after {
  bottom: -4px;
  opacity: 1;
  visibility: visible;
}

[WP V0RT3X]

Edit ONLY your custom css template.

[Motofumi Suzuki]

Thank you so much.