/* ═══ 返回顶部 + 评论区 ═══ */
.back-top { position: fixed; right: 22px; bottom: 26px; width: 40px; height: 40px; border-radius: 50%; background: var(--accent); color: #fff; display: flex; align-items: center; justify-content: center; font-size: 17px; cursor: pointer; opacity: 0; pointer-events: none; transform: translateY(8px); transition: opacity .25s, transform .25s; z-index: 90; box-shadow: 0 4px 14px rgba(0,0,0,.15); }
.back-top.show { opacity: .92; pointer-events: auto; transform: none; }
.back-top:hover { opacity: 1; }
.giscus-box { margin-top: 36px; padding-top: 22px; border-top: 1px solid var(--border); }
.giscus-title { font-size: 13px; letter-spacing: 1px; color: var(--ink-4); margin-bottom: 4px; }
@media (prefers-color-scheme: dark) { .back-top { background: #E0884F; } }