.back-to-top{position:fixed;right:24px;bottom:24px;z-index:90;display:flex;align-items:center;justify-content:center;width:48px;height:48px;padding:0;border:1px solid rgba(255,255,255,.28);border-radius:50%;background:#234f7f;color:#fff;box-shadow:0 10px 28px rgba(17,27,51,.24);font:700 1.45rem/1 system-ui,-apple-system,"Segoe UI",sans-serif;cursor:pointer;opacity:0;visibility:hidden;pointer-events:none;transform:translateY(10px);transition:opacity .2s,visibility .2s,transform .2s,background .2s}
.back-to-top.is-visible{opacity:1;visibility:visible;pointer-events:auto;transform:translateY(0)}
.back-to-top:hover{background:#10203f}
.back-to-top:focus-visible{outline:3px solid #cda744;outline-offset:3px}
@media(max-width:768px){.back-to-top{right:16px;bottom:16px;width:44px;height:44px;font-size:1.3rem}}
@media(prefers-reduced-motion:reduce){.back-to-top{transition:none}}