.back-to-top{position:fixed;right:24px;bottom:24px;z-index:40;width:48px;height:48px;border-radius:50%;border:1px solid var(--border);background:var(--surface);color:var(--fg);display:inline-flex;align-items:center;justify-content:center;cursor:pointer;box-shadow:var(--shadow-md);opacity:0;transform:translateY(8px);pointer-events:none;transition:opacity .15s,transform .15s,background-color .15s,color .15s}.back-to-top--visible{opacity:1;transform:translateY(0);pointer-events:auto}.back-to-top:hover{background:var(--primary);color:var(--primary-fg);border-color:var(--primary)}@media (max-width:640px){.back-to-top{right:16px;bottom:16px}}@media (prefers-reduced-motion:reduce){.back-to-top{transition:opacity .001ms,transform .001ms}}