.back-to-top{z-index:9999;position:fixed;width:40px;height:40px;background-color:rgba(0,0,0,.3);font-size:20px;line-height:40px;text-align:center;color:#fff;top:auto;left:auto;right:50px;bottom:30px;cursor:pointer;border-radius:2px}.back-to-top:hover{background-color:#a9c948}