/* ===== CSS 变量 ===== */
:root {
  --primary: #A855F7;
  --primary-dark: #8E3FD6;
  --primary-light: #C995FF;
  --bg: #faf9fc;
  --bg-card: #ffffff;
  --text: #1a1a2e;
  --text-secondary: #6b7280;
  --text-muted: #9ca3af;
  --border: #e5e7eb;
  --shadow: 0 4px 16px rgba(0,0,0,0.1);
  --shadow-hover: 0 8px 32px rgba(168,85,247,0.2);
  --radius: 12px;
  --spacing: 24px;
  --max-width: 1400px;
}
[data-theme="dark"] {
  --bg: #0f172a;
  --bg-card: #1e293b;
  --text: #e2e8f0;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border: #334155;
  --shadow: 0 4px 16px rgba(0,0,0,0.3);
  --shadow-hover: 0 8px 32px rgba(168,85,247,0.35);
}

/* ===== 重置 ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: "Noto Sans SC", -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", sans-serif;
  background: var(--bg); color: var(--text); line-height: 1.7;
  transition: background 0.3s, color 0.3s;
}
a { color: inherit; text-decoration: none; }
img { max-width: 100%; height: auto; display: block; }
ul, ol { list-style: none; }
button { cursor: pointer; border: none; background: none; font: inherit; color: inherit; }
input { font: inherit; }

.page-wrapper { max-width: var(--max-width); margin: 0 auto; padding: 0 var(--spacing); }

/* ===== 响应式 ===== */
@media (max-width: 1400px) { :root { --max-width: 100%; } }
@media (max-width: 768px) { :root { --spacing: 16px; } }
@media (max-width: 480px) { :root { --spacing: 12px; } }

/* ===== Section 标题 ===== */
.section-title {
  font-size: 1.4rem; font-weight: 700;
  margin-bottom: var(--spacing); padding-left: 14px;
  border-left: 4px solid var(--primary);
  display: flex; align-items: center; justify-content: space-between;
}

/* ===== Header ===== */
.site-header { background: var(--bg-card); border-bottom: 1px solid var(--border); box-shadow: 0 1px 4px rgba(0,0,0,0.04); }
.site-header .header-inner {
  max-width: var(--max-width); margin: 0 auto; padding: 16px var(--spacing);
  display: flex; align-items: center; justify-content: space-between;
}
.site-logo { font-size: 1.8rem; font-weight: 800; color: var(--primary); letter-spacing: 2px; white-space: nowrap; }
.site-logo span { color: var(--text-secondary); font-weight: 400; font-size: 0.78rem; margin-left: 10px; letter-spacing: 0; }
.header-nav { display: flex; gap: 28px; }
.header-nav a { font-size: 0.95rem; color: var(--text-secondary); transition: color 0.2s; padding: 4px 0; border-bottom: 2px solid transparent; }
.header-nav a:hover, .header-nav a.active { color: var(--primary); border-bottom-color: var(--primary); }
.header-search { display: flex; align-items: center; background: var(--bg); border: 1px solid var(--border); border-radius: 24px; padding: 8px 18px; transition: border-color 0.3s, box-shadow 0.3s; }
.header-search:focus-within { border-color: var(--primary); box-shadow: 0 0 0 3px rgba(168,85,247,0.12); }
.header-search input { border: none; background: transparent; outline: none; width: 200px; font-size: 0.9rem; color: var(--text); }
.header-search input::placeholder { color: var(--text-muted); }
.header-search button { font-size: 0.9rem; color: var(--primary); font-weight: 600; padding: 4px 8px; }
@media (max-width: 768px) { .header-nav { display: none; } .header-search input { width: 140px; } }

/* ===== Hero Banner ===== */
.hero-banner { max-width: var(--max-width); margin: var(--spacing) auto 0; position: relative; border-radius: var(--radius); overflow: hidden; height: 400px; }
.hero-slide { position: absolute; inset: 0; opacity: 0; transition: opacity 0.6s ease; display: flex; align-items: flex-end; background-size: cover; background-position: center 20%; background-color: var(--primary-dark); }
.hero-slide.active { opacity: 1; }
.hero-info { background: linear-gradient(transparent, rgba(0,0,0,0.85)); padding: 56px 32px 32px; width: 100%; color: #fff; }
.hero-info h1 { font-size: 2rem; margin-bottom: 12px; font-weight: 800; }
.hero-info p { font-size: 0.95rem; opacity: 0.88; margin-bottom: 12px; max-width: 650px; }
.hero-info .hero-meta { font-size: 0.85rem; opacity: 0.7; }
.hero-dots { position: absolute; bottom: 20px; right: 28px; display: flex; gap: 10px; z-index: 10; }
.hero-dots button { width: 12px; height: 12px; border-radius: 50%; background: rgba(255,255,255,0.35); transition: background 0.3s, transform 0.3s; }
.hero-dots button.active { background: #fff; transform: scale(1.3); }
@media (max-width: 768px) { .hero-banner { height: 260px; border-radius: 0; } .hero-info { padding: 36px 20px 20px; } .hero-info h1 { font-size: 1.4rem; } .hero-info p { font-size: 0.85rem; } }

/* ===== Stats Dashboard ===== */
.stats-section { max-width: var(--max-width); margin: 0 auto; padding: var(--spacing); }
.stats-grid { display: grid; grid-template-columns: repeat(6, 1fr); gap: var(--spacing); }
.stat-card { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 24px 16px; text-align: center; box-shadow: var(--shadow); transition: transform 0.3s, box-shadow 0.3s; }
.stat-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); }
.stat-card .stat-icon { width: 44px; height: 44px; margin: 0 auto 10px; border-radius: 50%; background: var(--primary-light); position: relative; }
.stat-card .stat-icon::after { content: ''; position: absolute; inset: 10px; border-radius: 2px; background: var(--primary); }
.stat-icon-books::after { border-radius: 3px 3px 0 0; inset: 8px 10px 12px; }
.stat-icon-views::after { border-radius: 50%; inset: 8px; }
.stat-icon-comments::after { border-radius: 3px; inset: 8px 10px; clip-path: polygon(50% 0%, 100% 38%, 82% 100%, 18% 100%, 0% 38%); }
.stat-icon-today::after { inset: 8px 10px; border-radius: 2px; }
.stat-icon-week::after { inset: 8px; border-radius: 2px; background: linear-gradient(var(--primary) 0%, var(--primary) 40%, transparent 40%, transparent 60%, var(--primary) 60%, var(--primary) 100%); }
.stat-icon-month::after { border-radius: 50%; inset: 6px; background: conic-gradient(var(--primary) 70%, transparent 70%); }
.stat-card .stat-value { font-size: 1.6rem; font-weight: 800; color: var(--primary); margin-bottom: 6px; }
.stat-card .stat-label { font-size: 0.82rem; color: var(--text-muted); }
@media (max-width: 992px) { .stats-grid { grid-template-columns: repeat(3, 1fr); } }
@media (max-width: 480px) { .stats-grid { grid-template-columns: repeat(2, 1fr); } }

/* ===== Service Guarantees (M-O24) ===== */
.guarantee-section { max-width: var(--max-width); margin: 0 auto; padding: 0 var(--spacing); margin-bottom: calc(var(--spacing) * 1.5); }
.guarantee-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: var(--spacing); }
.guarantee-item { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 28px 18px 22px; text-align: center; box-shadow: var(--shadow); transition: transform 0.3s, box-shadow 0.3s; }
.guarantee-item:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); }
.guarantee-icon { width: 52px; height: 52px; margin: 0 auto 14px; border-radius: 50%; position: relative; }
.guarantee-icon-auth { background: #ede9fe; }
.guarantee-icon-auth::after { content: ''; position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); width: 20px; height: 24px; border: 3px solid var(--primary); border-radius: 4px 4px 2px 2px; border-top: none; }
.guarantee-icon-auth::before { content: ''; position: absolute; top: 14px; left: 50%; transform: translateX(-50%); width: 12px; height: 8px; border-left: 3px solid var(--primary); border-bottom: 3px solid var(--primary); transform: translate(-50%,0) rotate(-45deg); z-index: 1; }
.guarantee-icon-speed { background: #fef3c7; }
.guarantee-icon-speed::after { content: ''; position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); width: 0; height: 0; border-left: 14px solid var(--primary); border-top: 10px solid transparent; border-bottom: 10px solid transparent; }
.guarantee-icon-quality { background: #dbeafe; }
.guarantee-icon-quality::after { content: ''; position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); width: 22px; height: 22px; border: 3px solid var(--primary); border-radius: 50%; }
.guarantee-icon-quality::before { content: ''; position: absolute; top: 50%; left: 32%; width: 4px; height: 4px; border-radius: 50%; background: var(--primary); z-index: 1; }
.guarantee-icon-service { background: #d1fae5; }
.guarantee-icon-service::after { content: ''; position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); width: 18px; height: 14px; border: 3px solid var(--primary); border-radius: 3px; }
.guarantee-item h4 { font-size: 1rem; font-weight: 700; margin-bottom: 8px; color: var(--text); }
.guarantee-item p { font-size: 0.82rem; color: var(--text-muted); line-height: 1.7; }
@media (max-width: 992px) { .guarantee-grid { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 480px) { .guarantee-grid { grid-template-columns: 1fr; } }

/* ===== Category Tags ===== */
.category-tags { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: calc(var(--spacing) * 1.5); padding: 8px 0; }
.category-tags .tag-btn { padding: 8px 22px; border-radius: 24px; border: 1px solid var(--border); font-size: 0.9rem; color: var(--text-secondary); background: var(--bg-card); transition: all 0.25s; }
.category-tags .tag-btn:hover, .category-tags .tag-btn.active { background: var(--primary); color: #fff; border-color: var(--primary); box-shadow: 0 2px 8px rgba(168,85,247,0.3); }

/* ===== Featured Comics ===== */
.featured-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: var(--spacing); margin-bottom: calc(var(--spacing) * 2); }
.featured-card { background: var(--bg-card); border-radius: var(--radius); overflow: hidden; box-shadow: var(--shadow); transition: transform 0.35s, box-shadow 0.35s; }
.featured-card:hover { transform: scale(1.03); box-shadow: var(--shadow-hover); }
.featured-card .cover-wrap { position: relative; aspect-ratio: 3/4; overflow: hidden; background: var(--border); }
.featured-card .cover-wrap img { width: 100%; height: 100%; object-fit: cover; transition: transform 0.35s; }
.featured-card:hover .cover-wrap img { transform: scale(1.08); }
.cover-overlay { position: absolute; bottom: 0; left: 0; right: 0; padding: 36px 12px 10px; background: linear-gradient(transparent, rgba(0,0,0,0.78)); }
.cover-overlay .overlay-title { color: #fff; font-size: 0.92rem; font-weight: 700; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.cover-overlay .overlay-meta { color: rgba(255,255,255,0.75); font-size: 0.7rem; margin-top: 2px; }
.featured-card .card-body { padding: 14px; }
.featured-card .comic-name { font-size: 1rem; font-weight: 700; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.featured-card .comic-author { font-size: 0.8rem; color: var(--text-muted); margin-bottom: 6px; }
.featured-card .comic-desc { font-size: 0.8rem; color: var(--text-secondary); line-height: 1.5; margin-bottom: 10px; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.featured-card .comic-meta { display: flex; flex-wrap: wrap; gap: 10px; font-size: 0.78rem; color: var(--text-secondary); align-items: center; }
.featured-card .comic-rating { color: #f59e0b; font-weight: 600; }
.featured-card .comic-heat { color: var(--primary); }
.status-tag { display: inline-block; padding: 2px 10px; border-radius: 12px; font-size: 0.72rem; font-weight: 600; }
.status-ongoing { background: #f3e8ff; color: #7c3aed; }
.status-completed { background: #d1fae5; color: #059669; }
[data-theme="dark"] .status-ongoing { background: #4c1d95; color: #c4b5fd; }
[data-theme="dark"] .status-completed { background: #064e3b; color: #34d399; }
@media (max-width: 1200px) { .featured-grid { grid-template-columns: repeat(3, 1fr); } }
@media (max-width: 768px) { .featured-grid { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 480px) { .featured-grid { grid-template-columns: repeat(2, 1fr); } }

/* ===== Top 5 Weekly Ranking ===== */
.top5-grid { display: flex; gap: var(--spacing); margin-bottom: calc(var(--spacing) * 2); overflow-x: auto; padding-bottom: 8px; }
.top5-card { flex: 1; min-width: 220px; background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px; text-align: center; box-shadow: var(--shadow); transition: transform 0.35s, box-shadow 0.35s; }
.top5-card:hover { transform: scale(1.03); box-shadow: var(--shadow-hover); }
.top5-rank { font-size: 1.6rem; font-weight: 800; margin-bottom: 10px; }
.rank-1st { color: #f59e0b; font-size: 2rem; }
.rank-2nd { color: #94a3b8; font-size: 1.8rem; }
.rank-3rd { color: #d97706; font-size: 1.6rem; }
.top5-card .top5-rank:not(.rank-1st):not(.rank-2nd):not(.rank-3rd) { color: var(--text-muted); }
.top5-cover { width: 120px; height: 160px; border-radius: 8px; object-fit: cover; margin: 0 auto 12px; }
.top5-info { min-width: 0; }
.top5-title { font-size: 1rem; font-weight: 700; display: block; margin-bottom: 4px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.top5-meta { font-size: 0.8rem; color: var(--text-muted); margin-bottom: 4px; }
.top5-heat { font-size: 0.85rem; color: var(--primary); font-weight: 600; }
@media (max-width: 992px) { .top5-grid { flex-wrap: wrap; } .top5-card { min-width: 160px; flex: 1 1 160px; } }
@media (max-width: 480px) { .top5-card { min-width: 140px; flex: 1 1 140px; padding: 14px; } }

/* ===== Partners (M-O22) ===== */
.partners-section { margin-bottom: calc(var(--spacing) * 2); }
.partners-grid { display: flex; flex-wrap: wrap; gap: var(--spacing); justify-content: center; }
.partner-item { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px 28px; text-align: center; min-width: 160px; box-shadow: var(--shadow); transition: transform 0.3s; }
.partner-item:hover { transform: translateY(-3px); }
.partner-logo { width: 64px; height: 64px; margin: 0 auto 10px; border-radius: 12px; }
.partner-logo-1 { background: linear-gradient(135deg, #a855f7, #7c3aed); }
.partner-logo-2 { background: linear-gradient(135deg, #06b6d4, #0891b2); }
.partner-logo-3 { background: linear-gradient(135deg, #f59e0b, #d97706); }
.partner-logo-4 { background: linear-gradient(135deg, #10b981, #059669); }
.partner-logo-5 { background: linear-gradient(135deg, #ec4899, #db2777); }
.partner-logo-6 { background: linear-gradient(135deg, #6366f1, #4f46e5); }
.partner-item span { font-size: 0.95rem; font-weight: 600; color: var(--text); }
.partner-item p { font-size: 0.78rem; color: var(--text-muted); margin-top: 4px; }

/* ===== User Reviews (M-O21) ===== */
.reviews-section { margin-bottom: calc(var(--spacing) * 2); }
.reviews-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: var(--spacing); }
.review-card { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px 22px; box-shadow: var(--shadow); border-left: 4px solid var(--primary); }
.review-card .review-text { font-size: 0.9rem; color: var(--text-secondary); line-height: 1.8; font-style: italic; margin-bottom: 10px; }
.review-card .review-author { font-size: 0.8rem; color: var(--primary); font-weight: 600; font-style: normal; }
@media (max-width: 768px) { .reviews-grid { grid-template-columns: 1fr; } }

/* ===== Completed Section ===== */
.completed-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: var(--spacing); margin-bottom: calc(var(--spacing) * 2); }
.completed-card { background: var(--bg-card); border-radius: var(--radius); overflow: hidden; box-shadow: var(--shadow); transition: transform 0.35s, box-shadow 0.35s; }
.completed-card:hover { transform: scale(1.03); box-shadow: var(--shadow-hover); }
.completed-card .cover-wrap { position: relative; aspect-ratio: 3/4; overflow: hidden; }
.completed-card .cover-wrap img { width: 100%; height: 100%; object-fit: cover; transition: transform 0.35s; }
.completed-card:hover .cover-wrap img { transform: scale(1.08); }
.badge-completed { position: absolute; top: 10px; right: 10px; background: #059669; color: #fff; font-size: 0.7rem; font-weight: 700; padding: 3px 10px; border-radius: 4px; }
.completed-card .card-info { padding: 12px 14px; }
.completed-card .comic-name { font-size: 0.92rem; font-weight: 600; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; display: block; }
.completed-card .comic-meta-sm { font-size: 0.75rem; color: var(--text-muted); margin-top: 6px; }
@media (max-width: 992px) { .completed-grid { grid-template-columns: repeat(3, 1fr); } }
@media (max-width: 480px) { .completed-grid { grid-template-columns: repeat(2, 1fr); } }

/* ===== FAQ ===== */
.faq-section { margin-bottom: calc(var(--spacing) * 2); }
.faq-list { display: flex; flex-direction: column; gap: 14px; }
.faq-item { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; transition: border-color 0.3s; }
.faq-item[open] { border-color: var(--primary); }
.faq-question { padding: 18px 22px; font-weight: 600; font-size: 0.95rem; cursor: pointer; list-style: none; display: flex; justify-content: space-between; align-items: center; user-select: none; color: var(--text); }
.faq-question::-webkit-details-marker { display: none; }
.faq-question::after { content: '+'; font-size: 1.3rem; color: var(--text-muted); transition: transform 0.3s; flex-shrink: 0; margin-left: 14px; font-weight: 300; }
.faq-item[open] .faq-question::after { content: '\2212'; color: var(--primary); transform: rotate(180deg); }
.faq-question:hover { color: var(--primary); }
.faq-answer { padding: 0 22px 18px; font-size: 0.88rem; color: var(--text-secondary); line-height: 1.9; }

/* ===== About Us (M-B5) ===== */
.about-section { margin-bottom: calc(var(--spacing) * 2); }
.about-intro { font-size: 0.92rem; color: var(--text-secondary); line-height: 2; margin-bottom: calc(var(--spacing) * 2); }
.about-intro p { margin-bottom: var(--spacing); }
.about-features { display: grid; grid-template-columns: repeat(4, 1fr); gap: var(--spacing); margin-bottom: calc(var(--spacing) * 2); }
.feature-item { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 24px 18px; text-align: center; box-shadow: var(--shadow); }
.feature-icon { width: 56px; height: 56px; margin: 0 auto 12px; border-radius: 50%; position: relative; }
.feature-icon-resources { background: #ede9fe; }
.feature-icon-resources::after { content: ''; position: absolute; inset: 10px; border: 2px solid var(--primary); border-radius: 3px 3px 6px 6px; border-top: 3px solid var(--primary); }
.feature-icon-hd { background: #dbeafe; }
.feature-icon-hd::after { content: ''; position: absolute; inset: 10px; border: 2px solid var(--primary); border-radius: 50%; }
.feature-icon-smooth { background: #d1fae5; }
.feature-icon-smooth::after { content: ''; position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); width: 22px; height: 0; border-top: 2px solid var(--primary); box-shadow: 0 6px 0 var(--primary), 0 12px 0 var(--primary); }
.feature-icon-free { background: #fef3c7; }
.feature-icon-free::after { content: ''; position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); width: 18px; height: 22px; border: 2px solid var(--primary); border-radius: 50%; border-bottom: 3px solid var(--primary); border-bottom-left-radius: 3px; border-bottom-right-radius: 3px; }
.feature-item h4 { font-size: 1rem; font-weight: 700; margin-bottom: 8px; color: var(--text); }
.feature-item p { font-size: 0.82rem; color: var(--text-muted); line-height: 1.6; }
.about-commitment { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 24px; margin-bottom: var(--spacing); }
.about-commitment h3 { font-size: 1.1rem; font-weight: 700; margin-bottom: 16px; color: var(--text); }
.about-commitment li { padding: 8px 0; font-size: 0.9rem; color: var(--text-secondary); border-bottom: 1px dashed var(--border); }
.about-commitment li:last-child { border-bottom: none; }
.about-contact { font-size: 0.9rem; color: var(--text-secondary); padding: 20px; background: var(--bg); border-radius: var(--radius); line-height: 1.8; }
.about-contact p { margin-bottom: 6px; }
.about-contact p:last-child { margin-bottom: 0; }
@media (max-width: 992px) { .about-features { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 480px) { .about-features { grid-template-columns: 1fr; } }

/* ===== Disclaimer (M-O23) ===== */
.disclaimer-section { margin-bottom: calc(var(--spacing) * 2); }
.disclaimer-content { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 24px; font-size: 0.88rem; color: var(--text-secondary); line-height: 2; }
.disclaimer-content p { margin-bottom: 12px; }
.disclaimer-content p:last-child { margin-bottom: 0; }

/* ===== Footer ===== */
.site-footer { background: var(--bg-card); border-top: 1px solid var(--border); padding: 32px 0; text-align: center; font-size: 0.85rem; color: var(--text-secondary); }
.site-footer .footer-inner { max-width: var(--max-width); margin: 0 auto; padding: 0 var(--spacing); }
.site-footer p { margin-bottom: 6px; }

/* ===== Theme Toggle ===== */
.theme-toggle { position: fixed; bottom: 88px; right: 24px; width: 44px; height: 44px; border-radius: 50%; background: var(--bg-card); border: 1px solid var(--border); box-shadow: var(--shadow); display: flex; align-items: center; justify-content: center; z-index: 99; transition: transform 0.3s, box-shadow 0.3s; }
.theme-toggle:hover { transform: scale(1.1); box-shadow: var(--shadow-hover); }
.toggle-icon { width: 20px; height: 20px; border-radius: 50%; background: var(--text-secondary); position: relative; transition: background 0.3s, box-shadow 0.3s; }
.toggle-icon::after { content: ''; position: absolute; top: -3px; left: 6px; width: 8px; height: 8px; border-radius: 50%; background: var(--bg-card); }
[data-theme="dark"] .toggle-icon { background: #f59e0b; box-shadow: 0 0 4px rgba(245,158,11,0.5); }
[data-theme="dark"] .toggle-icon::after { top: 4px; left: 2px; width: 6px; height: 6px; }

/* ===== Back to Top ===== */
.back-to-top { position: fixed; bottom: 28px; right: 24px; width: 44px; height: 44px; border-radius: 50%; background: var(--primary); color: #fff; display: flex; align-items: center; justify-content: center; box-shadow: var(--shadow); z-index: 99; opacity: 0; visibility: hidden; transition: opacity 0.3s, visibility 0.3s, transform 0.3s; }
.back-to-top.visible { opacity: 1; visibility: visible; }
.back-to-top:hover { transform: scale(1.1); }
.top-arrow { font-size: 1.2rem; line-height: 1; font-weight: 700; }