.back-to-top{display:none;position:fixed;bottom:20px;right:20px;background-color:#007bff;color:#fff;padding:10px 15px;border:none;border-radius:5px;cursor:pointer;z-index:9999;box-shadow:0 2px 5px rgba(0,0,0,0.2);transition:opacity 0.3s}.back-to-top.show{display:block}