discourse/app/assets/stylesheets/common/base/share_link.scss

// styles that apply to the "share" popup when sharing a link to a post or topic

#share-link {
  position: absolute;
  left: 20px;
  z-index: 990;
  box-shadow: 0 1px 5px rgba($primary, .4);
  background-color: scale-color($primary, $lightness: 90%);
  padding: 6px 10px 10px 10px;
  width: 300px;
  display: none;
  &.visible {
    display: block;
  }
  input[type=text] {
    width: 96%;
  }
  h3 {
    font-size: 13px;
  }
  .social-link {
    margin-left: 2px;
    margin-right: 8px;
    float: left;
    font-size: 22px;
  }
  .link {
    margin-right: 2px;
    float: right;
    font-size: 20px;
    a {
      color: $primary;
    }
  }
}