discourse/app/assets/stylesheets/common/components/navs.css.scss

// --------------------------------------------------
// Navigation menus
// --------------------------------------------------

// Base
// --------------------------------------------------

%nav {
  margin-left: 0;
  list-style: none;
  li > a {
    display: block;
    text-decoration: none;
  }
}

// Pill nav
// --------------------------------------------------

.nav-pills {
  @extend %nav;
  @extend .clearfix;
  > li {
    float: left;
    margin-right: 5px;
    > a {
      border: none;
      padding: 5px 12px;
      color: $primary;
      font-size: 1.143em;
      line-height: 20px;
      transition: background .15s;
      &:hover {
        color: $quaternary;
        background-color: dark-light-diff($quaternary, $secondary, 70%, -70%);
      }
    }
    &.active > a, > a.active {
      color: $secondary;
      background-color: $quaternary;
    }
  }
}

// Stacked nav
// --------------------------------------------------

.nav-stacked {
  @extend %nav;
  padding: 0;
  overflow: hidden;
  background: dark-light-diff($primary, $secondary, 90%, -75%);
  li {
    border-bottom: 1px solid dark-light-diff($primary, $secondary, 80%, -60%);
    position: relative;
    &:last-of-type {
      border-bottom: 0;
    }
    > a {
      margin: 0;
      padding: 13px 13px 13px 30px;
      font-size: 1.143em;
      line-height: 20px;
      cursor: pointer;
      color: $primary;
    }
  }
  .active > a, & li > a.active
  {
    color: $secondary;
    background-color: $quaternary;
  }

  .active > a::after, & li > a.active::after
  {
    left: 90%;
    top: 33%;
    content: " ";
    position: absolute;
    border: 8px solid transparent;
    border-left-color: $secondary;
  }

  .count {
    font-size: 0.857em;
    line-height: 16px;
  }

  .glyph {
    font-size: 0.857em;
    width: 30px;
    text-align: center;
    position: absolute;
    left: 2px;
    line-height: 20px;
  }
}