.cd-top {
  height:auto;
  width: 40px;
  position: fixed;
  bottom:130px;
  right: 0px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.05);
  /* image replacement properties */
  overflow: hidden;
  -webkit-transition: all 0.3s;
  -moz-transition: all 0.3s;
  transition: all 0.3s;
 }
.cd-top img{ width:100%;}
.cd-top.cd-is-visible {
  /* the button becomes visible */
  visibility: visible;
  opacity: 1;
}
.cd-top.cd-fade-out {
  /* 如果用户继续向下滚动,这个按钮的透明度会变得更低 */
  opacity: .5;
}
.no-touch .cd-top:hover {
  opacity: 1;
}
@media only screen and (min-width: 768px) {
  .cd-top {
    right: 20px;
    bottom: 30px;
  }
}
@media only screen and (min-width: 1024px) {
  .cd-top {
    height: 60px;
    width: 60px;
    right: 30px;
    bottom:60px;
  }
}