.back-to-top-btn{position:fixed;bottom:30px;left:45px;background-color:#134f5c;color:#fff;border:none;border-radius:50%;width:50px;height:50px;font-size:20px;cursor:pointer;display:flex;justify-content:center;align-items:center;box-shadow:0 4px 8px #0003;z-index:999;opacity:0;visibility:hidden;transform:translateY(20px);transition:opacity .3s ease,visibility .3s ease,transform .3s ease}.back-to-top-btn.show{opacity:1;visibility:visible;transform:translateY(0)}.back-to-top-btn:hover{background-color:#218da5}