#pagetop {
  position: fixed;
  right: 40px;
  bottom: 20px;
  z-index: 5500;
  display: block;
  width: 42px;
  height:42px;
  cursor: pointer;
  background: rgba(0, 0, 0, .5);
  border: 1px solid #ffffff;
  border-radius: 4px;
  opacity: 0;
  transition: .5s;
}
#pagetop.visible {
  opacity: 1;
  pointer-events: auto;
}
#pagetop span {
  position: absolute;
  top: 16px;
  left: 11px;
  display: block;
  width:18px;
  height:18px;
  content:"";
  border-top:3px solid #ffffff;
  border-right:3px solid #ffffff;
  -webkit-transform: rotate(315deg);
  transform: rotate(315deg);
}