#backtop {
  position: fixed;
  left: auto;
  right: 20px;
  top: auto;
  bottom: 20px;
  outline: none;
  overflow: hidden;
  color: #fff;
  text-align: center;
  background-color: #0a4f2bb0;
  height: 40px;
  width: 40px;
  line-height: 40px;
  font-size: 14px;
  border-radius: 2px;
  cursor: pointer;
  transition: all 0.2s linear;
  z-index: 999999;
  opacity: 1;
  display: none;
}

#backtop:hover {
  background-color: #009246;
}

#backtop.mcOut {
  opacity: 0;
}