.back-to-top{background-color:#f90;border:none;border-radius:5px;bottom:20px;color:#fff;cursor:pointer;display:none;font-size:20px;height:50px;line-height:normal;padding:10px 15px;position:fixed;right:20px;transition:opacity .3s,visibility .3s;width:50px;z-index:999999}.back-to-top i{left:50%;position:absolute;top:50%;transform:translate(-50%,-50%);vertical-align:middle}.back-to-top:hover{background-color:#ec8505}