#back-to-top {
  position: fixed;
  bottom: 40px;
  right: 40px;
  z-index: 9999;
  width: 32px;
  height: 32px;
  text-align: center;
  line-height: 30px;
  background: #fff;
  color: #444;
  cursor: pointer;
  border: 0;
  border-radius: .25rem;
  text-decoration: none;
  transition: opacity 0.2s ease-out;
  display: none;
  -webkit-box-shadow: 0px 2px 6px -4px rgba(0,0,0,0.59);
  -moz-box-shadow: 0px 2px 6px -4px rgba(0,0,0,0.59);
  box-shadow: 0px 2px 6px -4px rgba(0,0,0,0.59);
  border: 1px solid transparent;
}
#back-to-top:hover {
  border: 1px solid #e9ebec;
}
#back-to-top.show {
  display: block;
}