.cd-top {
	display: inline-block;
	height: 40px;
	width: 40px;
	position: fixed;
	bottom: 40px;
	right: 10px;
	box-shadow: 0 0 10px rgba(0, 0, 0, 0.05);
	/* image replacement properties */
	overflow: hidden;
	text-indent: 100%;
	white-space: nowrap;
	visibility: hidden;
	opacity: 0;
	-webkit-transition: all 0.3s;
	-moz-transition: all 0.3s;
	transition: all 0.3s;
	background-color: rgba(0,102,204,0.8);
	background-image: url(../images/cd-top-arrow.svg);
	background-repeat: no-repeat;
	background-position: center 50%;
}
.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 {
  background-color: #e86256;
  opacity: 1;
}
@media only screen and (min-width: 768px) {
  .cd-top {
    right: 20px;
    bottom: 20px;
  }
}
@media only screen and (min-width: 1024px) {
  .cd-top {
    height: 60px;
    width: 60px;
    right: 30px;
    bottom: 30px;
  }
}