/* ================================
   CSS 变量和基础设置
================================ */

:root {
  /* 柬埔寨文化色彩系统 */
  --khmer-red: #A52A2A;        /* 高棉红 - 主色 */
  --deep-sea-blue: #192A56;    /* 深海蓝 - 辅色 */
  --angkor-gold: #E4C15D;      /* 吴哥金 - 点缀色 */
  --charcoal: #333333;         /* 炭黑 - 文字色 */
  --off-white: #FDFBF5;        /* 米白 - 背景色 */
  --light-gray: #EAEAEA;       /* 浅灰 - 中性色 */
  
  /* 语义化颜色 */
  --primary-color: var(--khmer-red);
  --secondary-color: var(--deep-sea-blue);
  --accent-color: var(--angkor-gold);
  --text-color: var(--charcoal);
  --bg-color: var(--off-white);
  --border-color: var(--light-gray);
  
  /* 字体系统 */
  --font-primary: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', '微软雅黑', sans-serif;
  --font-heading: 'Noto Sans SC', 'Montserrat', sans-serif;
  
  /* 间距系统 */
  --spacing-xs: 0.5rem;    /* 8px */
  --spacing-sm: 1rem;      /* 16px */
  --spacing-md: 1.5rem;    /* 24px */
  --spacing-lg: 2rem;      /* 32px */
  --spacing-xl: 3rem;      /* 48px */
  --spacing-2xl: 4rem;     /* 64px */
  
  /* 断点 */
  --mobile: 768px;
  --tablet: 992px;
  --desktop: 1200px;
  
  /* 阴影系统 */
  --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);
  
  /* 过渡效果 */
  --transition-fast: 0.2s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
}

/* ================================
   全局重置和基础样式
================================ */

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-primary);
  color: var(--text-color);
  background-color: var(--bg-color);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

a {
  color: var(--primary-color);
  text-decoration: none;
  transition: var(--transition-fast);
}

a:hover {
  color: var(--secondary-color);
  text-decoration: underline;
}

/* ================================
   容器和布局
================================ */

.container {
  max-width: var(--desktop);
  margin: 0 auto;
  padding: 0 var(--spacing-sm);
}

@media (min-width: 768px) {
  .container {
    padding: 0 var(--spacing-lg);
  }
}

/* ================================
   导航栏
================================ */

.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background: var(--secondary-color);
  z-index: 1000;
  padding: var(--spacing-sm) 0;
  transition: var(--transition-normal);
}

.nav-container {
  max-width: var(--desktop);
  margin: 0 auto;
  padding: 0 var(--spacing-sm);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.nav-brand h1 {
  color: var(--off-white);
  font-size: 1.5rem;
  font-weight: 700;
  font-family: var(--font-heading);
}

.nav-menu {
  display: flex;
  gap: var(--spacing-lg);
}

.nav-link {
  color: var(--off-white);
  font-weight: 500;
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: 4px;
  transition: var(--transition-fast);
  position: relative;
}

.nav-link:hover,
.nav-link.active {
  color: var(--accent-color);
  text-decoration: none;
}

.nav-link.active::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: var(--spacing-sm);
  right: var(--spacing-sm);
  height: 2px;
  background: var(--accent-color);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  cursor: pointer;
}

.bar {
  width: 25px;
  height: 3px;
  background: var(--off-white);
  margin: 2px 0;
  transition: var(--transition-fast);
}

/* 移动端导航 */
@media (max-width: 767px) {
  .nav-menu {
    position: fixed;
    top: 70px;
    left: -100%;
    flex-direction: column;
    background: var(--secondary-color);
    width: 100%;
    padding: var(--spacing-lg);
    transition: var(--transition-normal);
    box-shadow: var(--shadow-lg);
  }
  
  .nav-menu.active {
    left: 0;
  }
  
  .nav-toggle {
    display: flex;
  }
  
  .nav-toggle.active .bar:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
  }
  
  .nav-toggle.active .bar:nth-child(2) {
    opacity: 0;
  }
  
  .nav-toggle.active .bar:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -6px);
  }
}

/* ================================
   Hero 区域
================================ */

.hero {
  height: 100vh;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  color: white;
  overflow: hidden;
}

.hero-background {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -2;
}

.hero-image {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.hero-overlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(135deg, rgba(25, 42, 86, 0.7), rgba(165, 42, 42, 0.6));
  z-index: -1;
}

.hero-content {
  max-width: 800px;
  padding: 0 var(--spacing-sm);
  animation: fadeInUp 1s ease-out;
}

.hero-title {
  font-size: clamp(2.5rem, 5vw, 4rem);
  font-weight: 700;
  margin-bottom: var(--spacing-sm);
  font-family: var(--font-heading);
  text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

.hero-subtitle {
  font-size: clamp(1.2rem, 3vw, 1.8rem);
  margin-bottom: var(--spacing-md);
  color: var(--accent-color);
  font-weight: 600;
}

.hero-description {
  font-size: 1.1rem;
  margin-bottom: var(--spacing-xl);
  opacity: 0.9;
  line-height: 1.6;
}

.hero-actions {
  display: flex;
  gap: var(--spacing-sm);
  justify-content: center;
  flex-wrap: wrap;
}

.scroll-indicator {
  position: absolute;
  bottom: var(--spacing-lg);
  left: 50%;
  transform: translateX(-50%);
  animation: bounce 2s infinite;
}

.scroll-arrow {
  width: 24px;
  height: 24px;
  border: 2px solid white;
  border-top: none;
  border-left: none;
  transform: rotate(45deg);
}

/* ================================
   柬埔寨Hero区域
================================ */

.cambodia-hero {
  height: 60vh;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  color: white;
  margin-top: 70px;
}

.cambodia-hero .hero-background {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -2;
}

.cambodia-hero .hero-overlay {
  background: linear-gradient(135deg, rgba(25, 42, 86, 0.8), rgba(165, 42, 42, 0.7));
}

/* ================================
   按钮样式
================================ */

.btn {
  display: inline-block;
  padding: var(--spacing-sm) var(--spacing-lg);
  border-radius: 8px;
  font-weight: 600;
  text-decoration: none;
  transition: var(--transition-normal);
  cursor: pointer;
  border: none;
  font-size: 1rem;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.btn-primary {
  background: var(--accent-color);
  color: var(--charcoal);
  box-shadow: var(--shadow-md);
}

.btn-primary:hover {
  background: #f0d06b;
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  text-decoration: none;
  color: var(--charcoal);
}

.btn-secondary {
  background: transparent;
  color: white;
  border: 2px solid white;
}

.btn-secondary:hover {
  background: white;
  color: var(--secondary-color);
  text-decoration: none;
}

.btn-gold {
  background: var(--accent-color);
  color: var(--charcoal);
  box-shadow: var(--shadow-md);
}

.btn-gold:hover {
  background: #f0d06b;
  transform: translateY(-2px);
  text-decoration: none;
  color: var(--charcoal);
}

/* ================================
   区域标题
================================ */

.section-title {
  font-size: clamp(2rem, 4vw, 2.5rem);
  font-weight: 700;
  color: var(--secondary-color);
  margin-bottom: var(--spacing-md);
  font-family: var(--font-heading);
  position: relative;
}

.section-title::after {
  content: '';
  display: block;
  width: 60px;
  height: 4px;
  background: var(--accent-color);
  margin: var(--spacing-sm) auto 0;
}

.section-subtitle {
  font-size: 1.2rem;
  color: var(--text-color);
  opacity: 0.8;
  margin-bottom: var(--spacing-xl);
  text-align: center;
}

/* ================================
   关于我区域
================================ */

.about {
  padding: var(--spacing-2xl) 0;
  background: white;
}

.about-content {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-xl);
  align-items: center;
}

@media (min-width: 768px) {
  .about-content {
    grid-template-columns: 2fr 1fr;
  }
}

.about-intro h3 {
  font-size: 1.5rem;
  color: var(--primary-color);
  margin-bottom: var(--spacing-sm);
  font-weight: 600;
}

.about-description {
  font-size: 1.1rem;
  margin-bottom: var(--spacing-md);
  line-height: 1.8;
}

.about-mission {
  font-style: italic;
  color: var(--secondary-color);
  border-left: 4px solid var(--accent-color);
  padding-left: var(--spacing-sm);
  margin-bottom: var(--spacing-lg);
}

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: var(--spacing-md);
  margin-top: var(--spacing-lg);
}

.stat-item {
  text-align: center;
  padding: var(--spacing-sm);
}

.stat-number {
  font-size: 2rem;
  font-weight: 700;
  color: var(--primary-color);
  display: block;
}

.stat-label {
  font-size: 0.9rem;
  color: var(--text-color);
  opacity: 0.8;
  margin-top: var(--spacing-xs);
}

/* B站数据实时更新样式 */
.stats.loading {
  opacity: 0.7;
  pointer-events: none;
}

.stats.loading .stat-number {
  animation: pulse 1.5s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

.stat-number {
  transition: all 0.3s ease;
}

.stat-number:hover {
  transform: scale(1.05);
}

.stats-update {
  text-align: center;
  margin-top: var(--spacing-sm);
}

.update-time {
  font-size: 0.75rem;
  color: var(--text-color);
  opacity: 0.6;
  font-style: italic;
}

.about-image {
  display: flex;
  justify-content: center;
}

.image-placeholder {
  width: 200px;
  height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.avatar-frame {
  width: 150px;
  height: 150px;
  background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-lg);
}

.avatar-text {
  color: white;
  font-weight: 700;
  font-size: 1.2rem;
}

/* ================================
   视频区域
================================ */

.videos {
  padding: var(--spacing-2xl) 0;
  background: var(--bg-color);
}

.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
}

.video-card {
  background: white;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: var(--shadow-md);
  transition: var(--transition-normal);
  cursor: pointer;
}

.video-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.video-thumbnail {
  width: 100%;
  height: 200px;
  background: var(--light-gray);
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
}

.video-placeholder {
  width: 100%;
  height: 100%;
  background: linear-gradient(135deg, var(--secondary-color), var(--primary-color));
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 3rem;
}

.video-info {
  padding: var(--spacing-sm);
}

.video-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-color);
  margin-bottom: var(--spacing-xs);
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.video-meta {
  font-size: 0.9rem;
  color: var(--text-color);
  opacity: 0.7;
}

.video-actions {
  text-align: center;
}

/* ================================
   柬埔寨介绍区域
================================ */

.cambodia-intro {
  padding: var(--spacing-2xl) 0;
  background: white;
}

.cambodia-content {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-xl);
  align-items: center;
}

@media (min-width: 768px) {
  .cambodia-content {
    grid-template-columns: 1fr 1fr;
  }
}

.cambodia-description {
  font-size: 1.1rem;
  line-height: 1.8;
  margin-bottom: var(--spacing-lg);
}

.features {
  display: grid;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
}

.feature-item h4 {
  color: var(--primary-color);
  margin-bottom: var(--spacing-xs);
  font-weight: 600;
}

.feature-item p {
  color: var(--text-color);
  opacity: 0.8;
  font-size: 0.95rem;
}

.image-gallery {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-sm);
}

.gallery-image {
  width: 100%;
  height: 150px;
  object-fit: cover;
  border-radius: 8px;
  box-shadow: var(--shadow-sm);
  transition: var(--transition-normal);
}

.gallery-image:hover {
  transform: scale(1.05);
  box-shadow: var(--shadow-md);
}

.gallery-image:first-child {
  grid-column: 1 / -1;
  height: 200px;
}

/* ================================
   页面内导航
================================ */

.page-nav {
  background: var(--bg-color);
  padding: var(--spacing-sm) 0;
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 70px;
  z-index: 100;
}

.nav-anchors {
  display: flex;
  justify-content: center;
  gap: var(--spacing-lg);
  flex-wrap: wrap;
}

.anchor-link {
  padding: var(--spacing-xs) var(--spacing-sm);
  color: var(--text-color);
  font-weight: 500;
  border-radius: 20px;
  transition: var(--transition-fast);
}

.anchor-link:hover {
  background: var(--primary-color);
  color: white;
  text-decoration: none;
}

/* ================================
   概览区域
================================ */

.overview {
  padding: var(--spacing-2xl) 0;
  background: white;
}

.overview-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--spacing-lg);
}

.overview-card {
  background: var(--bg-color);
  padding: var(--spacing-lg);
  border-radius: 12px;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border-color);
  transition: var(--transition-normal);
}

.overview-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.overview-card h3 {
  color: var(--secondary-color);
  margin-bottom: var(--spacing-sm);
  font-weight: 600;
  font-size: 1.2rem;
}

.info-item {
  margin-bottom: var(--spacing-xs);
  line-height: 1.6;
}

.info-item strong {
  color: var(--primary-color);
  font-weight: 600;
}

/* ================================
   历史时间线
================================ */

.history {
  padding: var(--spacing-2xl) 0;
  background: var(--bg-color);
}

.timeline {
  position: relative;
  max-width: 800px;
  margin: 0 auto;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 50%;
  top: 0;
  bottom: 0;
  width: 4px;
  background: var(--accent-color);
  transform: translateX(-50%);
}

.timeline-item {
  position: relative;
  margin-bottom: var(--spacing-xl);
  display: flex;
  align-items: center;
}

.timeline-item:nth-child(odd) {
  flex-direction: row;
}

.timeline-item:nth-child(even) {
  flex-direction: row-reverse;
}

.timeline-date {
  width: 120px;
  text-align: center;
  font-weight: 700;
  color: var(--primary-color);
  background: white;
  padding: var(--spacing-xs);
  border-radius: 20px;
  box-shadow: var(--shadow-sm);
  position: relative;
  z-index: 2;
}

.timeline-content {
  flex: 1;
  background: white;
  padding: var(--spacing-lg);
  margin: 0 var(--spacing-lg);
  border-radius: 12px;
  box-shadow: var(--shadow-md);
  position: relative;
}

.timeline-content h3 {
  color: var(--secondary-color);
  margin-bottom: var(--spacing-sm);
  font-weight: 600;
}

.timeline-content p {
  line-height: 1.7;
  color: var(--text-color);
}

/* 移动端时间线 */
@media (max-width: 767px) {
  .timeline::before {
    left: 20px;
  }
  
  .timeline-item {
    flex-direction: row !important;
    padding-left: 50px;
  }
  
  .timeline-date {
    position: absolute;
    left: -50px;
    width: 80px;
    font-size: 0.8rem;
  }
  
  .timeline-content {
    margin: 0;
  }
}

/* ================================
   文化区域
================================ */

.culture {
  padding: var(--spacing-2xl) 0;
  background: white;
}

.culture-grid {
  display: grid;
  gap: var(--spacing-2xl);
}

.culture-section {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-lg);
  align-items: center;
}

@media (min-width: 768px) {
  .culture-section {
    grid-template-columns: 1fr 1fr;
  }
  
  .culture-section.reverse {
    direction: rtl;
  }
  
  .culture-section.reverse > * {
    direction: ltr;
  }
}

.culture-image {
  border-radius: 12px;
  overflow: hidden;
  box-shadow: var(--shadow-md);
}

.culture-image img {
  width: 100%;
  height: 300px;
  object-fit: cover;
  transition: var(--transition-slow);
}

.culture-image:hover img {
  transform: scale(1.05);
}

.culture-content h3 {
  color: var(--secondary-color);
  margin-bottom: var(--spacing-sm);
  font-size: 1.5rem;
  font-weight: 600;
}

.culture-content p {
  line-height: 1.8;
  margin-bottom: var(--spacing-md);
}

.festivals {
  margin-top: var(--spacing-2xl);
}

.festivals h3 {
  color: var(--secondary-color);
  margin-bottom: var(--spacing-lg);
  font-size: 1.5rem;
  font-weight: 600;
  text-align: center;
}

.festival-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-lg);
}

.festival-card {
  background: var(--bg-color);
  padding: var(--spacing-lg);
  border-radius: 12px;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border-color);
  transition: var(--transition-normal);
}

.festival-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent-color);
}

.festival-card h4 {
  color: var(--primary-color);
  margin-bottom: var(--spacing-xs);
  font-weight: 600;
}

.festival-card p {
  font-size: 0.9rem;
  line-height: 1.6;
  margin-bottom: var(--spacing-xs);
}

.etiquette {
  margin-top: var(--spacing-2xl);
  background: var(--bg-color);
  padding: var(--spacing-xl);
  border-radius: 12px;
}

.etiquette h3 {
  color: var(--secondary-color);
  margin-bottom: var(--spacing-sm);
  font-size: 1.5rem;
  font-weight: 600;
}

.etiquette-content p {
  margin-bottom: var(--spacing-lg);
  line-height: 1.8;
}

.etiquette-rules {
  display: grid;
  gap: var(--spacing-md);
}

.rule-item {
  padding: var(--spacing-sm);
  background: white;
  border-radius: 8px;
  border-left: 4px solid var(--accent-color);
}

.rule-item strong {
  color: var(--primary-color);
}

/* ================================
   现代发展区域
================================ */

.modern {
  padding: var(--spacing-2xl) 0;
  background: var(--bg-color);
}

.modern-content {
  display: grid;
  gap: var(--spacing-2xl);
}

.modern-section {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-lg);
  align-items: center;
}

@media (min-width: 768px) {
  .modern-section {
    grid-template-columns: 1fr 1fr;
  }
  
  .modern-section.reverse {
    direction: rtl;
  }
  
  .modern-section.reverse > * {
    direction: ltr;
  }
}

.modern-image {
  border-radius: 12px;
  overflow: hidden;
  box-shadow: var(--shadow-md);
}

.modern-image img {
  width: 100%;
  height: 300px;
  object-fit: cover;
}

.modern-text h3 {
  color: var(--secondary-color);
  margin-bottom: var(--spacing-sm);
  font-size: 1.5rem;
  font-weight: 600;
}

.modern-text p {
  line-height: 1.8;
  margin-bottom: var(--spacing-md);
}

.modern-text ul {
  padding-left: var(--spacing-lg);
}

.modern-text li {
  margin-bottom: var(--spacing-xs);
  line-height: 1.6;
}

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

.development-stats {
  margin-top: var(--spacing-2xl);
  text-align: center;
}

.development-stats h3 {
  color: var(--secondary-color);
  margin-bottom: var(--spacing-lg);
  font-size: 1.5rem;
  font-weight: 600;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--spacing-lg);
}

.stat-card {
  background: white;
  padding: var(--spacing-lg);
  border-radius: 12px;
  box-shadow: var(--shadow-md);
  transition: var(--transition-normal);
}

.stat-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.stat-card .stat-number {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--primary-color);
  margin-bottom: var(--spacing-xs);
}

.stat-card .stat-label {
  font-size: 0.9rem;
  color: var(--text-color);
  opacity: 0.8;
}

/* ================================
   页脚
================================ */

.footer {
  background: var(--secondary-color);
  color: var(--off-white);
  padding: var(--spacing-2xl) 0 var(--spacing-lg);
}

.footer-content {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-lg);
}

.footer h3,
.footer h4 {
  color: var(--accent-color);
  margin-bottom: var(--spacing-sm);
  font-weight: 600;
}

.footer p {
  line-height: 1.6;
  opacity: 0.9;
}

.footer ul {
  list-style: none;
}

.footer li {
  margin-bottom: var(--spacing-xs);
}

.footer a {
  color: var(--off-white);
  transition: var(--transition-fast);
}

.footer a:hover {
  color: var(--accent-color);
  text-decoration: none;
}

/* ================================
   返回顶部按钮
================================ */

.back-to-top {
  position: fixed;
  bottom: var(--spacing-lg);
  right: var(--spacing-lg);
  background: var(--primary-color);
  color: white;
  width: 50px;
  height: 50px;
  border-radius: 50%;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-lg);
  transition: var(--transition-normal);
  opacity: 0;
  visibility: hidden;
  z-index: 1000;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  background: var(--secondary-color);
  transform: translateY(-2px);
}

/* ================================
   动画
================================ */

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

@keyframes bounce {
  0%, 20%, 50%, 80%, 100% {
    transform: translateX(-50%) translateY(0);
  }
  40% {
    transform: translateX(-50%) translateY(-10px);
  }
  60% {
    transform: translateX(-50%) translateY(-5px);
  }
}

/* ================================
   视频嵌入响应式
================================ */

.video-responsive {
  position: relative;
  overflow: hidden;
  width: 100%;
  padding-top: 56.25%; /* 16:9 Aspect Ratio */
  border-radius: 8px;
  background: var(--light-gray);
}

.video-responsive iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: 0;
  border-radius: 8px;
}

/* ================================
   加载动画
================================ */

.loading {
  display: inline-block;
  width: 20px;
  height: 20px;
  border: 3px solid var(--border-color);
  border-radius: 50%;
  border-top-color: var(--primary-color);
  animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ================================
   可访问性改进
================================ */

@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

:focus-visible {
  outline: 2px solid var(--accent-color);
  outline-offset: 2px;
}

/* ================================
   打印样式
================================ */

@media print {
  .navbar,
  .back-to-top,
  .hero-actions,
  .video-actions {
    display: none;
  }
  
  .hero {
    height: auto;
    page-break-inside: avoid;
  }
  
  body {
    font-size: 12pt;
    line-height: 1.4;
  }
  
  h1, h2, h3 {
    page-break-after: avoid;
  }
}