.back-to-top{position:fixed;bottom:24px;right:24px;z-index:900;width:44px;height:44px;border-radius:50%;border:none;background:rgba(0,0,0,.6);color:#fff;cursor:pointer;display:flex;align-items:center;justify-content:center;box-shadow:0 2px 8px rgba(0,0,0,.2);transition:opacity .3s,background .2s}.back-to-top:hover{background:rgba(0,0,0,.8)}@media(max-width:991px){.back-to-top{bottom:90px}}