www.moparisthebest.com/.themes/classic/sass/partials/sidebar/_base.scss

.side-shadow-border {
  @include box-shadow(lighten($sidebar-bg, 5) 0 1px);
}
aside[role=sidebar] {
  color: $sidebar-color;
  text-shadow: lighten($sidebar-bg, 8) 0 1px;
  a { @extend .force-wrap; }
  section {
    @extend .sans;
    font-size: .8em;
    line-height: 1.4em;
    margin-bottom: 1.5em;
    h1 {
      margin: 1.5em 0 0;
      padding-bottom: .2em;
      border-bottom: 1px solid $sidebar-border;
      @extend .side-shadow-border;
      + p {
        padding-top: .4em;
      }
    }
  }
  ul {
    margin-bottom: 0.5em;
    margin-left: 0;
  }
  li {
    list-style: none;
    padding: .5em 0;
    margin: 0;
    border-bottom: 1px solid $sidebar-border;
    @extend .side-shadow-border;
    p:last-child {
      margin-bottom: 0;
    }
  }
  a {
    color: inherit;
    @include transition(color .5s);
  }
  &:hover a {
    color: $sidebar-link-color;
    &:hover { color: $sidebar-link-color-hover; }
  }
}
.aside-alt-link {
  color: $sidebar-link-color-subdued;
  &:hover {
    color: $sidebar-link-color-subdued-hover;
  }
}

@media only screen and (min-width: 768px) {
  .toggle-sidebar {
    outline: none;
    position: absolute; right: -10px; top: 0; bottom: 0;
    display: inline-block;
    text-decoration: none;
    color: mix($text-color-light, $sidebar-bg);
    width: 9px;
    cursor: pointer;
    &:hover {
      background: mix($sidebar-border, $sidebar-bg);
      @include background(linear-gradient(left, rgba($sidebar-border, .5), rgba($sidebar-border, 0)));
    }
    &:after {
      position: absolute; right: -11px; top: 0;
      width: 20px;
      font-size: 1.2em;
      line-height: 1.1em;
      padding-bottom: .15em;
      @include border-bottom-right-radius(.3em);
      text-align: center;
      background: $main-bg $noise-bg;
      border-bottom: 1px solid $sidebar-border;
      border-right: 1px solid $sidebar-border;
      content: "\00BB";
      text-indent: -1px;
    }
    .collapse-sidebar & {
      text-indent: 0px;
      right: -20px;
      width: 19px;
      &:hover {
        background: mix($sidebar-border, $sidebar-bg);
      }
      &:after {
        border-left: 1px solid $sidebar-border;
        text-shadow: #fff 0 1px;
        content: "\00AB";
        left: 0px; right: 0;
        text-align: center;
        text-indent: 0;
        border: 0;
        border-right-width: 0;
        background: none;
      }
    }
  }
}