.back-to-top{background-color:#333;border-radius:5px;bottom:20px;color:#fff;cursor:pointer;font-size:18px;opacity:0;padding:10px 15px;position:fixed;right:20px;text-align:center;text-decoration:none;transition:opacity .5s ease;visibility:hidden;z-index:1000}.back-to-top.show{opacity:1;visibility:visible}