/* ============================================================
   北仑区自贸创新指南 - 样式文件
   设计风格：政务蓝 + 现代简约 + 双栏政策卡片
   ============================================================ */

:root {
  --primary: #0066b3;
  --primary-dark: #004d8a;
  --primary-light: #3b82c9;
  --primary-50: #e8f2fa;
  --primary-100: #d1e5f4;
  --accent: #00a0e9;
  --text-dark: #1a2b3c;
  --text-body: #334155;
  --text-muted: #64748b;
  --text-light: #94a3b8;
  --bg-white: #ffffff;
  --bg-gray: #f5f7fa;
  --bg-silver: #f0f2f5;
  --border-light: #e2e8f0;
  --shadow-sm: 0 1px 3px rgba(0, 102, 179, 0.06);
  --shadow-md: 0 4px 20px rgba(0, 102, 179, 0.08);
  --shadow-lg: 0 12px 40px rgba(0, 102, 179, 0.12);
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei",
    "Helvetica Neue", Helvetica, Arial, sans-serif;
  color: var(--text-body);
  line-height: 1.75;
  background: var(--bg-white);
  overflow-x: hidden;
}

.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 40px;
}

/* ============================================================
   导航栏
   ============================================================ */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-light);
  transition: all 0.3s ease;
}

.navbar.scrolled {
  box-shadow: var(--shadow-md);
}

.nav-container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 40px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 70px;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 18px;
  font-weight: 600;
  color: var(--primary);
  letter-spacing: 2px;
}

.nav-logo img {
  height: 36px;
  border-radius: 6px;
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: 8px;
}

.nav-menu li { position: relative; }

.nav-link {
  display: block;
  padding: 10px 18px;
  color: var(--text-body);
  text-decoration: none;
  font-size: 15px;
  font-weight: 500;
  border-radius: 6px;
  transition: all 0.25s ease;
}

.nav-link:hover,
.nav-link.active {
  color: var(--primary);
  background: var(--primary-50);
}

.dropdown {
  position: absolute;
  top: 100%;
  left: 0;
  min-width: 180px;
  list-style: none;
  background: #fff;
  border-radius: 8px;
  box-shadow: var(--shadow-lg);
  padding: 8px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: all 0.25s ease;
}

.has-dropdown:hover .dropdown {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.dropdown li a {
  display: block;
  padding: 10px 16px;
  color: var(--text-body);
  text-decoration: none;
  font-size: 14px;
  border-radius: 6px;
  transition: all 0.2s ease;
}

.dropdown li a:hover {
  background: var(--primary-50);
  color: var(--primary);
}

/* ============================================================
   Hero 封面区
   ============================================================ */
.hero {
  position: relative;
  height: 100vh;
  min-height: 680px;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, #0066b3 0%, #004d8a 50%, #003366 100%);
  z-index: 0;
}

.hero-bg::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image: url('images/图片-01.jpg');
  background-size: cover;
  background-position: center;
  opacity: 0.25;
  mix-blend-mode: overlay;
}

.hero-bg::after {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 20% 30%, rgba(0, 160, 233, 0.3) 0%, transparent 50%),
    radial-gradient(circle at 80% 70%, rgba(0, 102, 179, 0.4) 0%, transparent 50%);
}

.hero-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg,
    rgba(0, 51, 102, 0.1) 0%,
    rgba(0, 51, 102, 0.4) 100%);
  z-index: 1;
}

.hero-content {
  position: relative;
  z-index: 2;
  text-align: center;
  color: #fff;
  max-width: 900px;
  padding: 0 40px;
}

.hero-year {
  font-size: 72px;
  font-weight: 200;
  letter-spacing: 8px;
  opacity: 0.7;
  margin-bottom: 10px;
  animation: fadeInDown 1s ease;
}

.hero-title {
  font-size: 48px;
  font-weight: 600;
  line-height: 1.4;
  letter-spacing: 4px;
  margin-bottom: 24px;
  animation: fadeInUp 1s ease 0.2s both;
}

.hero-title .highlight {
  background: linear-gradient(90deg, #4fc3f7, #81d4fa);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 14px;
  font-weight: 300;
  opacity: 0.8;
  letter-spacing: 1px;
  margin-bottom: 40px;
  animation: fadeInUp 1s ease 0.4s both;
}

.hero-divider {
  width: 80px;
  height: 3px;
  background: linear-gradient(90deg, transparent, #4fc3f7, transparent);
  margin: 0 auto 30px;
  animation: fadeIn 1s ease 0.6s both;
}

.hero-publisher {
  font-size: 15px;
  font-weight: 400;
  opacity: 0.9;
  letter-spacing: 4px;
  animation: fadeInUp 1s ease 0.8s both;
}

.hero-scroll {
  position: absolute;
  bottom: 40px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 2;
  text-align: center;
  color: rgba(255, 255, 255, 0.7);
  font-size: 12px;
  letter-spacing: 3px;
  animation: float 3s ease-in-out infinite;
}

.scroll-arrow {
  width: 24px;
  height: 24px;
  margin: 12px auto 0;
  border-right: 2px solid rgba(255, 255, 255, 0.5);
  border-bottom: 2px solid rgba(255, 255, 255, 0.5);
  transform: rotate(45deg);
}

.hero-cityline {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 120px;
  background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 1200 120'%3E%3Cpath d='M0 120V90l40-5v-15l25-10 15 10v15l30-20 20 10v20l25-30 20 5 15 25v30l30-40 20 10v30l25-25 20 10 10 15v20l30-50 25 15 15 35v20l20-45 20 10 15 35v20l25-30 15 10v20l20-15 10 15v20l30-40 20 20v20l25-35 20 15 10 20v20l30-50 25 25v25l20-30 15 10v20l25-25 20 10 10 15v25l30-45 20 15 15 30v20l25-35 20 10 10 25v20l30-50 25 20v30l20-35 15 15 10 20v20l25-30 20 10 10 20v20l30-40 20 20v20h0z' fill='rgba(255,255,255,0.08)'/%3E%3C/svg%3E") bottom center / cover no-repeat;
  z-index: 1;
  opacity: 0.6;
}

@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeInDown {
  from { opacity: 0; transform: translateY(-30px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes float {
  0%, 100% { transform: translateX(-50%) translateY(0); }
  50% { transform: translateX(-50%) translateY(-10px); }
}

/* ============================================================
   目录区
   ============================================================ */
.toc-section {
  padding: 120px 0;
  background: var(--bg-white);
}

.section-header {
  text-align: center;
  margin-bottom: 80px;
}

.section-en {
  display: block;
  font-size: 14px;
  color: var(--text-light);
  letter-spacing: 6px;
  margin-bottom: 8px;
}

.section-title {
  font-size: 48px;
  font-weight: 300;
  color: var(--text-dark);
  letter-spacing: 12px;
  position: relative;
  display: inline-block;
}

.section-title::before {
  content: '';
  position: absolute;
  left: 50%;
  bottom: -16px;
  transform: translateX(-50%);
  width: 60px;
  height: 3px;
  background: var(--primary);
}

.toc-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 30px;
  max-width: 1000px;
  margin: 0 auto;
}

.toc-item {
  display: flex;
  gap: 30px;
  padding: 40px;
  background: var(--bg-white);
  border: 1px solid var(--border-light);
  border-radius: 12px;
  text-decoration: none;
  color: inherit;
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
}

.toc-item::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 100%;
  background: var(--primary);
  transform: scaleY(0);
  transition: transform 0.3s ease;
}

.toc-item:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--primary-100);
}

.toc-item:hover::before {
  transform: scaleY(1);
}

.toc-item.toc-main {
  grid-column: span 2;
  background: linear-gradient(135deg, var(--primary-50) 0%, #fff 100%);
  border-color: var(--primary-100);
}

.toc-num {
  font-size: 56px;
  font-weight: 200;
  color: var(--primary);
  line-height: 1;
  flex-shrink: 0;
  opacity: 0.8;
}

.toc-info h3 {
  font-size: 20px;
  font-weight: 600;
  color: var(--text-dark);
  margin-bottom: 8px;
}

.toc-item.toc-main .toc-info h3 {
  font-size: 24px;
}

.toc-info > p {
  font-size: 14px;
  color: var(--text-muted);
  margin-bottom: 16px;
}

.toc-sub {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.toc-sub span {
  padding: 4px 12px;
  background: #fff;
  border: 1px solid var(--primary-100);
  border-radius: 20px;
  font-size: 13px;
  color: var(--primary);
}

/* ============================================================
   通用章节样式
   ============================================================ */
.part-label {
  display: flex;
  align-items: center;
  gap: 20px;
  margin-bottom: 40px;
}

.part-roman {
  font-size: 64px;
  font-weight: 200;
  color: var(--primary);
  line-height: 1;
  letter-spacing: -2px;
}

.part-line {
  flex: 1;
  height: 1px;
  background: linear-gradient(90deg, var(--primary-100), transparent);
  max-width: 400px;
}

.chapter-title {
  font-size: 32px;
  font-weight: 600;
  color: var(--text-dark);
  line-height: 1.4;
  margin-bottom: 10px;
  display: flex;
  align-items: flex-start;
  gap: 16px;
}

.chapter-title.center {
  justify-content: center;
  flex-direction: column;
  align-items: center;
  text-align: center;
}

.title-bar {
  display: inline-block;
  width: 5px;
  height: 1.3em;
  background: var(--primary);
  flex-shrink: 0;
  border-radius: 3px;
  margin-top: 4px;
}

.title-bar.center-bar {
  width: 60px;
  height: 4px;
  margin: 0 auto 20px;
  background: linear-gradient(90deg, transparent, var(--primary), transparent);
  border-radius: 2px;
}

.chapter-en {
  font-size: 13px;
  color: var(--text-light);
  letter-spacing: 1px;
  margin-bottom: 30px;
  margin-left: 21px;
  font-weight: 300;
}

/* ============================================================
   第一部分：片区概况
   ============================================================ */
.overview-section {
  padding: 100px 0;
  background: var(--bg-gray);
  position: relative;
}

.overview-section::before {
  content: '';
  position: absolute;
  top: 0;
  right: 0;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, var(--primary-50) 0%, transparent 70%);
  opacity: 0.5;
}

.overview-layout {
  display: grid;
  grid-template-columns: 1.2fr 1fr;
  gap: 60px;
  align-items: start;
  position: relative;
  z-index: 1;
}

.overview-content p {
  margin-bottom: 18px;
  color: var(--text-body);
  line-height: 1.9;
}

.overview-content strong {
  color: var(--primary);
  font-weight: 600;
}

.overview-image {
  position: sticky;
  top: 100px;
}

.overview-image img {
  width: 100%;
  border-radius: 12px;
  box-shadow: var(--shadow-lg);
}

.image-caption {
  margin-top: 12px;
  font-size: 13px;
  color: var(--text-muted);
  text-align: center;
}

.stats-grid {
  display: flex;
  align-items: center;
  justify-content: center;
  margin-top: 80px;
  padding: 50px;
  background: #fff;
  border-radius: 16px;
  box-shadow: var(--shadow-md);
  position: relative;
  z-index: 1;
}

.stat-card {
  flex: 1;
  text-align: center;
  padding: 0 20px;
}

.stat-num {
  font-size: 56px;
  font-weight: 300;
  color: var(--primary);
  line-height: 1.1;
  margin-bottom: 8px;
}

.stat-label {
  font-size: 14px;
  color: var(--text-muted);
  line-height: 1.6;
}

.stat-label small {
  font-size: 12px;
  color: var(--text-light);
}

.stat-divider {
  width: 1px;
  height: 60px;
  background: var(--border-light);
}

/* ============================================================
   第二部分：综合优势
   ============================================================ */
.advantages-section {
  padding: 100px 0;
  background: #fff;
}

.adv-block {
  margin-top: 80px;
}

.adv-header {
  display: flex;
  align-items: baseline;
  gap: 20px;
  margin-bottom: 30px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--primary-50);
}

.adv-num {
  font-size: 36px;
  font-weight: 300;
  color: var(--primary);
  opacity: 0.6;
}

.adv-header h3 {
  font-size: 26px;
  font-weight: 600;
  color: var(--text-dark);
}

.adv-body {
  display: grid;
  grid-template-columns: 1.1fr 1fr;
  gap: 50px;
  align-items: center;
}

.adv-body.reverse {
  grid-template-columns: 1fr 1.1fr;
}

.adv-body.reverse .adv-text {
  order: 2;
}

.adv-body.reverse .adv-image {
  order: 1;
}

.adv-text p {
  margin-bottom: 16px;
  color: var(--text-body);
  line-height: 1.9;
}

.adv-text strong {
  color: var(--primary);
}

.adv-image img {
  width: 100%;
  border-radius: 12px;
  box-shadow: var(--shadow-lg);
}

.industry-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  margin-top: 30px;
}

.ind-stat {
  padding: 20px;
  background: var(--bg-gray);
  border-radius: 10px;
  text-align: center;
  border-left: 3px solid var(--primary);
  transition: all 0.3s ease;
}

.ind-stat:hover {
  background: var(--primary-50);
  transform: translateY(-2px);
}

.ind-num {
  font-size: 32px;
  font-weight: 600;
  color: var(--primary);
  line-height: 1.1;
  margin-bottom: 6px;
}

.ind-num small {
  font-size: 16px;
  font-weight: 400;
}

.ind-label {
  font-size: 13px;
  color: var(--text-muted);
  line-height: 1.4;
}

.adv-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 30px;
  margin-top: 20px;
}

.strength-card {
  padding: 40px 30px;
  background: var(--bg-gray);
  border-radius: 12px;
  border-top: 4px solid var(--primary);
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
}

.strength-card::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -50%;
  width: 200px;
  height: 200px;
  background: radial-gradient(circle, var(--primary-50), transparent);
  opacity: 0;
  transition: opacity 0.3s ease;
}

.strength-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-lg);
}

.strength-card:hover::before {
  opacity: 1;
}

.strength-icon {
  width: 56px;
  height: 56px;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  position: relative;
  z-index: 1;
}

.strength-icon svg {
  width: 28px;
  height: 28px;
  color: #fff;
}

.strength-card h4 {
  font-size: 19px;
  font-weight: 600;
  color: var(--text-dark);
  margin-bottom: 14px;
  position: relative;
  z-index: 1;
}

.strength-card > p {
  font-size: 14px;
  color: var(--text-muted);
  line-height: 1.8;
  margin-bottom: 20px;
  position: relative;
  z-index: 1;
}

.strength-data {
  border-top: 1px solid var(--border-light);
  padding-top: 16px;
  position: relative;
  z-index: 1;
}

.strength-data span {
  display: block;
  font-size: 13px;
  color: var(--primary);
  font-weight: 500;
  margin-bottom: 6px;
}

/* ============================================================
   第三部分：政策指南
   ============================================================ */
.policies-section {
  padding: 100px 0;
  background: var(--bg-gray);
  position: relative;
}

.policy-tabs {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 12px;
  margin: 50px 0 60px;
  padding: 16px;
  background: #fff;
  border-radius: 12px;
  box-shadow: var(--shadow-sm);
}

.policy-tab {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  border: none;
  background: transparent;
  font-size: 15px;
  font-weight: 500;
  color: var(--text-body);
  cursor: pointer;
  border-radius: 8px;
  transition: all 0.25s ease;
  font-family: inherit;
}

.policy-tab:hover {
  background: var(--primary-50);
  color: var(--primary);
}

.policy-tab.active {
  background: var(--primary);
  color: #fff;
  box-shadow: 0 4px 12px rgba(0, 102, 179, 0.3);
}

.tab-icon {
  font-size: 12px;
  opacity: 0.7;
}

/* ============================================================
   政策面板与卡片
   ============================================================ */
.policy-tabs {
  position: relative;
  z-index: 10;
}

.policy-panels-wrapper {
  position: relative;
  min-height: 800px;
  contain: layout paint;
}

.policy-panel {
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: opacity 0.18s ease, transform 0.18s ease, visibility 0.18s;
  pointer-events: none;
  will-change: opacity, transform;
}

.policy-panel.active {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
  pointer-events: auto;
  position: relative;
}

.policy-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
  contain: layout paint;
}

.policy-card {
  background: #fff;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
  transition: transform 0.18s ease, box-shadow 0.18s ease, border-color 0.18s ease;
  border: 1px solid var(--border-light);
  transform: translateZ(0);
  backface-visibility: hidden;
  contain: layout paint;
}

.policy-card:hover {
  transform: translateY(-2px) translateZ(0);
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.08);
  border-color: var(--primary-100);
}

.policy-card.featured .policy-title {
  background: linear-gradient(135deg, var(--primary-dark), var(--primary));
}

.policy-card.featured .policy-icon {
  color: #ffd700;
}

.policy-title {
  background: linear-gradient(135deg, var(--primary), var(--primary-light));
  color: #fff;
  padding: 18px 24px;
  font-size: 16px;
  font-weight: 600;
  line-height: 1.5;
  display: flex;
  align-items: flex-start;
  gap: 10px;
}

.policy-icon {
  font-size: 18px;
  flex-shrink: 0;
  opacity: 0.9;
}

.policy-body {
  padding: 20px 24px;
}

.policy-row {
  margin-bottom: 16px;
  position: relative;
}

.policy-row:last-of-type {
  margin-bottom: 20px;
}

.row-label {
  display: inline-block;
  padding: 4px 12px;
  background: var(--primary-50);
  color: var(--primary);
  font-size: 13px;
  font-weight: 600;
  border-radius: 4px;
  margin-bottom: 8px;
  border-left: 3px solid var(--primary);
}

.row-content {
  font-size: 14px;
  color: var(--text-body);
  line-height: 1.8;
  padding-left: 8px;
}

.row-content.highlight {
  color: var(--text-dark);
  font-weight: 500;
  background: linear-gradient(90deg, var(--primary-50), transparent);
  padding: 10px 14px;
  border-radius: 6px;
  border-left: 3px solid var(--accent);
}

.policy-departments {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  padding-top: 16px;
  border-top: 1px dashed var(--border-light);
}

.policy-departments span {
  padding: 4px 10px;
  background: var(--bg-gray);
  border: 1px solid var(--border-light);
  border-radius: 4px;
  font-size: 12px;
  color: var(--text-muted);
  transition: all 0.2s ease;
}

.policy-card:hover .policy-departments span {
  background: var(--primary-50);
  color: var(--primary);
  border-color: var(--primary-100);
}

/* ============================================================
   页脚
   ============================================================ */
.footer {
  position: relative;
  background: linear-gradient(180deg, #003366 0%, #002244 100%);
  color: rgba(255, 255, 255, 0.8);
  padding-top: 100px;
}

.footer-cityline {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 100px;
  background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 1200 100'%3E%3Cpath d='M0 100V75l40-8v-12l25-8 15 8v12l30-16 20 8v16l25-24 20 4 15 20v24l30-32 20 8v24l25-20 20 8 10 12v16l30-40 25 12 15 28v16l20-36 20 8 15 28v16l25-24 15 8v16l20-12 10 12v16l30-32 20 16v16l25-28 20 12 10 16v16l30-40 25 20v20l20-24 15 8v16l25-20 20 8 10 12v20l30-36 20 12 15 24v16l25-28 20 8 10 20v16l30-40 25 16v24l20-28 15 12 10 16v16l25-24 20 8 10 16v16l30-32 20 16v16h0z' fill='rgba(255,255,255,0.06)'/%3E%3C/svg%3E") top center / cover no-repeat;
  opacity: 0.8;
}

.footer-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 60px 0;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: 16px;
}

.footer-logo {
  height: 50px;
  border-radius: 8px;
}

.footer-brand h4 {
  font-size: 20px;
  font-weight: 600;
  color: #fff;
  letter-spacing: 2px;
  margin-bottom: 2px;
}

.footer-brand p {
  font-size: 11px;
  opacity: 0.6;
  letter-spacing: 2px;
}

.footer-info {
  text-align: right;
}

.footer-title {
  font-size: 16px;
  color: #fff;
  font-weight: 500;
  margin-bottom: 8px;
}

.footer-info p {
  font-size: 13px;
  opacity: 0.7;
  line-height: 1.8;
}

.footer-date {
  margin-top: 6px;
  letter-spacing: 3px;
}

.footer-bottom {
  text-align: center;
  padding: 0 0 24px;
  font-size: 13px;
  opacity: 0.5;
}

/* ============================================================
   返回顶部
   ============================================================ */
.back-to-top {
  position: fixed;
  right: 30px;
  bottom: 30px;
  width: 48px;
  height: 48px;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 16px rgba(0, 102, 179, 0.3);
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);
  transition: all 0.3s ease;
  z-index: 999;
}

.back-to-top.show {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  background: var(--primary-dark);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0, 102, 179, 0.4);
}

.back-to-top svg {
  width: 20px;
  height: 20px;
}

/* ============================================================
   响应式
   ============================================================ */
@media (max-width: 1024px) {
  .container { padding: 0 24px; }
  .nav-container { padding: 0 24px; }
  .nav-menu { gap: 4px; }
  .nav-link { padding: 8px 12px; font-size: 14px; }

  .hero-title { font-size: 36px; }
  .hero-year { font-size: 56px; }
  .hero-subtitle { font-size: 12px; }

  .overview-layout { grid-template-columns: 1fr; gap: 40px; }
  .overview-image { position: static; }

  .toc-grid { grid-template-columns: 1fr; }
  .toc-item.toc-main { grid-column: span 1; }

  .adv-body,
  .adv-body.reverse { grid-template-columns: 1fr; gap: 30px; }
  .adv-body.reverse .adv-text { order: 1; }
  .adv-body.reverse .adv-image { order: 2; }

  .adv-cards { grid-template-columns: 1fr; gap: 20px; }
  .industry-stats { grid-template-columns: repeat(2, 1fr); }

  .policy-grid { grid-template-columns: 1fr; }

  .stats-grid { flex-wrap: wrap; padding: 30px; gap: 20px; }
  .stat-card { flex: 1 1 40%; padding: 10px; }
  .stat-divider { display: none; }

  .footer-content { flex-direction: column; gap: 30px; text-align: center; }
  .footer-info { text-align: center; }
}

@media (max-width: 640px) {
  .navbar { height: 60px; }
  .nav-logo span { display: none; }
  .nav-menu .nav-link { font-size: 13px; padding: 6px 10px; }
  .has-dropdown .dropdown { display: none; }

  .hero { min-height: 560px; }
  .hero-year { font-size: 42px; letter-spacing: 4px; }
  .hero-title { font-size: 26px; letter-spacing: 2px; line-height: 1.5; }

  .section-title { font-size: 32px; letter-spacing: 8px; }
  .chapter-title { font-size: 24px; }
  .part-roman { font-size: 42px; }

  .policy-tabs { padding: 10px; gap: 6px; }
  .policy-tab { padding: 10px 16px; font-size: 13px; }

  .toc-section, .overview-section, .advantages-section, .policies-section {
    padding: 60px 0;
  }

  .section-header { margin-bottom: 50px; }

  .stat-num { font-size: 40px; }
  .industry-stats { grid-template-columns: 1fr; }
}