@media screen and (max-width:768px) {
  header .menu {
    position: fixed;
    left: -100%;
    top: 0;
    width: 80%;
    height: 100vh;
    background: #fff;
    display: block;
    opacity: 0;
    overflow: auto;
    -webkit-transition: all ease .3s;
    -o-transition: all ease .3s;
    -moz-transition: all ease .3s;
    transition: all ease .3s;
    z-index: 50;
    color: #333;
  }

  header.open .menu {
    left: 0;
    opacity: 1;
  }

  header .menu::before {
    content: '';
    width: 20vw;
    display: block;
    height: 100vh;
    background: rgba(0, 0, 0, 0.4);
    position: fixed;
    left: -20vw;
    top: 0;
    z-index: 50;
    -webkit-transition: all ease .3s;
    -o-transition: all ease .3s;
    -moz-transition: all ease .3s;
    transition: all ease .3s;
  }

  header.open .menu::before {
    left: 80%;
  }

  header .link {
    width: 100%;
    margin-left: 0;
  }

  header .link>a {
    display: block;
    border-bottom: 1px solid #ddd;
    line-height: 50px;
  }

  header .link a {
    padding: 0 20px;
  }

  header .link::after {
    display: none;
    width: 52px;
    height: 10px;
    left: 50%;
    top: 100%;
    margin-top: 14px;
    -webkit-transform: translate(-50%, -50%) scale(0);
       -moz-transform: translate(-50%, -50%) scale(0);
         -o-transform: translate(-50%, -50%) scale(0);
            transform: translate(-50%, -50%) scale(0);
  }

  header .link:hover::after,
  header .link.on::after {
    -webkit-transform: translate(-50%, 0) scale(1);
       -moz-transform: translate(-50%, 0) scale(1);
         -o-transform: translate(-50%, 0) scale(1);
            transform: translate(-50%, 0) scale(1);
  }

  header .down {
    min-width: 80px;
    overflow: hidden;
    padding: 0;
  }

  header .link .down {
    left: 50%;
    top: 100%;
    margin-top: 0;
    -webkit-transform: translate(0, 0);
       -moz-transform: translate(0, 0);
         -o-transform: translate(0, 0);
            transform: translate(0, 0);
    min-width: 160px;
    padding: 0;
    border-radius: 0;
    -webkit-box-shadow: none;
            box-shadow: none;
    position: static;
    opacity: 1;
    width: 100%;
    pointer-events: visible;
    border-bottom: 1px solid #ddd;
    display: none;
  }

  header .link .down::before {
    width: 100%;
    height: 40px;
    bottom: 100%;
  }

  header .link .down a {
    padding: 10px 30px;
    text-align: left;
    font-size: 14px;
    color: #666;
  }

  header .link .down a:not(:last-child) {
    border-bottom: none;
  }

  header .link .down-jt {
    width: 50px;
    height: 50px;
    position: absolute;
    right: 0;
    top: 0;
    background: url('/img/icon-jia.svg') no-repeat center/15px;
  }


  header .link.on .down-jt {
    background: url('/img/icon-jian.svg') no-repeat center/15px;
  }
}