/*返回顶部*/
.back-to-top {
    position: fixed;
    z-index: 2;
    right: -108px;
    bottom: 0;
    width: 108px;
    height: 150px;
    background: url("../image/back-to-top.webp") no-repeat 0 0;
    background-size: 108px 450px;
    opacity: 0.6;
    transition: opacity 0.3s, right 0.8s;
  }
  .back-to-top:hover {
    background-position: 0 -150px;
    opacity: 1;
  }
  .back-to-top.load {
    right: 0;
  }
  .back-to-top.ani-leave {
    background-position: 0 -150px;
    animation: ani-leave 390ms ease-in-out;
    animation-fill-mode: forwards;
  }
  .back-to-top.leaved {
    pointer-events: none;
    background: none;
    transition: none;
  }
  .back-to-top.ending {
    pointer-events: none;
  }
  .back-to-top.ending::after {
    opacity: 1;
  }
  .back-to-top::after {
    content: '';
    position: fixed;
    z-index: 2;
    right: 0;
    bottom: 0;
    width: 108px;
    height: 150px;
    background: url("../image/back-to-top.webp") no-repeat 0 0;
    background-size: 108px 450px;
    background-position: 0 -300px;
    transition: opacity 0.3s;
    opacity: 0;
    pointer-events: none;
  }