/* =============================================
   红桃视频 - 主样式表 (外部CSS)
   ============================================= */

/* CSS变量 */
:root {
  --brand-red: #e8192c;
  --brand-red-dark: #c0111f;
  --brand-red-light: #ff4d5e;
  --brand-pink: #ff6b7a;
  --text-primary: #1a1a1a;
  --text-secondary: #555;
  --text-muted: #888;
  --bg-light: #f7f8fa;
  --bg-white: #fff;
  --border-color: #e8e8e8;
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.12);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --font-main: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
}

/* 重置 */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; }
body { font-family: var(--font-main); color: var(--text-primary); background: var(--bg-light); line-height: 1.6; }
a { color: inherit; text-decoration: none; }
a:hover { color: var(--brand-red); }
img { max-width: 100%; height: auto; display: block; }
ul { list-style: none; }

/* 容器 */
.container { max-width: 1200px; margin: 0 auto; padding: 0 16px; }

/* =============================================
   顶部品牌栏
   ============================================= */
.top-brand-bar {
  background: var(--brand-red);
  color: #fff;
  padding: 8px 0;
  font-size: 13px;
}
.top-brand-bar .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
}
.brand-logo-link {
  display: flex;
  align-items: center;
  gap: 8px;
  color: #fff;
  font-weight: 700;
  font-size: 18px;
}
.brand-logo-link .logo-icon { font-size: 20px; }
.top-bar-right {
  display: flex;
  align-items: center;
  gap: 16px;
  font-size: 12px;
  opacity: 0.9;
}
.top-slogan { font-weight: 500; }
.top-domain { opacity: 0.85; }

/* =============================================
   主导航
   ============================================= */
.main-nav {
  background: #fff;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
  position: sticky;
  top: 0;
  z-index: 100;
}
.main-nav .container {
  display: flex;
  align-items: center;
  height: 56px;
  gap: 0;
}
.nav-logo {
  flex-shrink: 0;
  margin-right: 24px;
}
.nav-logo a {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 20px;
  font-weight: 800;
  color: var(--brand-red);
}
.nav-logo-icon { font-size: 22px; }
.nav-logo-text { letter-spacing: -0.5px; }
.nav-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 22px;
  cursor: pointer;
  color: var(--text-primary);
  padding: 4px 8px;
  margin-left: auto;
}
.nav-menu {
  display: flex;
  align-items: center;
  gap: 2px;
  flex: 1;
}
.nav-item a {
  display: block;
  padding: 6px 14px;
  font-size: 14px;
  font-weight: 500;
  color: var(--text-secondary);
  border-radius: var(--radius-sm);
  transition: all 0.2s;
  white-space: nowrap;
}
.nav-item a:hover,
.nav-item.active a {
  color: var(--brand-red);
  background: #fff0f1;
}

/* =============================================
   搜索栏
   ============================================= */
.search-bar-wrap {
  background: #fff;
  border-top: 1px solid var(--border-color);
  padding: 12px 0;
}
.search-bar-wrap .container {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.search-form {
  display: flex;
  gap: 8px;
  position: relative;
}
.search-input {
  flex: 1;
  height: 42px;
  border: 2px solid var(--border-color);
  border-radius: 21px;
  padding: 0 20px;
  font-size: 14px;
  font-family: var(--font-main);
  outline: none;
  transition: border-color 0.2s;
  background: var(--bg-light);
}
.search-input:focus { border-color: var(--brand-red); background: #fff; }
.search-btn {
  height: 42px;
  padding: 0 20px;
  background: var(--brand-red);
  color: #fff;
  border: none;
  border-radius: 21px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  font-family: var(--font-main);
  display: flex;
  align-items: center;
  gap: 6px;
  transition: background 0.2s;
  white-space: nowrap;
}
.search-btn:hover { background: var(--brand-red-dark); }
.search-hot-tags {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
  font-size: 12px;
  color: var(--text-muted);
}
.search-hot-tags a {
  color: var(--text-secondary);
  padding: 2px 10px;
  background: var(--bg-light);
  border-radius: 12px;
  border: 1px solid var(--border-color);
  transition: all 0.2s;
}
.search-hot-tags a:hover { color: var(--brand-red); border-color: var(--brand-red); background: #fff0f1; }
.search-tip { font-size: 12px; color: var(--brand-red); margin-top: 4px; }

/* =============================================
   主内容区
   ============================================= */
.page-main { padding: 20px 0 40px; }
.section { margin-bottom: 32px; }
.section-header {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  margin-bottom: 20px;
  gap: 12px;
}
.section-title-wrap { flex: 1; }
.section-title {
  font-size: 22px;
  font-weight: 800;
  color: var(--text-primary);
  position: relative;
  padding-left: 14px;
  margin-bottom: 4px;
}
.section-title::before {
  content: '';
  position: absolute;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 4px;
  height: 22px;
  background: var(--brand-red);
  border-radius: 2px;
}
.section-subtitle { font-size: 13px; color: var(--text-muted); }
.section-more {
  font-size: 13px;
  color: var(--text-muted);
  white-space: nowrap;
  padding: 4px 12px;
  border: 1px solid var(--border-color);
  border-radius: 14px;
  transition: all 0.2s;
}
.section-more:hover { color: var(--brand-red); border-color: var(--brand-red); }

/* 面包屑 */
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 16px;
  flex-wrap: wrap;
}
.breadcrumb a { color: var(--text-muted); }
.breadcrumb a:hover { color: var(--brand-red); }
.breadcrumb .sep { color: #ccc; }
.breadcrumb .current { color: var(--text-primary); }

/* =============================================
   Hero Banner
   ============================================= */
.hero-section { margin-bottom: 32px; }
.hero-banner {
  position: relative;
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: #111;
}
.hero-banner img {
  width: 100%;
  height: 380px;
  object-fit: cover;
  display: block;
  opacity: 0.7;
}
.hero-overlay {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  padding: 40px 40px 32px;
  background: linear-gradient(to top, rgba(0,0,0,0.85) 0%, transparent 100%);
  color: #fff;
}
.hero-tag {
  display: inline-block;
  background: var(--brand-red);
  color: #fff;
  padding: 3px 12px;
  border-radius: 14px;
  font-size: 12px;
  font-weight: 700;
  margin-bottom: 10px;
}
.hero-title {
  font-size: 26px;
  font-weight: 800;
  line-height: 1.3;
  margin-bottom: 12px;
  text-shadow: 0 2px 8px rgba(0,0,0,0.3);
}
.hero-meta {
  display: flex;
  gap: 16px;
  font-size: 13px;
  opacity: 0.85;
  flex-wrap: wrap;
}

/* =============================================
   视频卡片
   ============================================= */
.video-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
}
.video-grid-3 { grid-template-columns: repeat(3, 1fr); }
.video-card {
  background: var(--bg-white);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
}
.video-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}
.video-thumb {
  position: relative;
  aspect-ratio: 16/9;
  overflow: hidden;
  background: #111;
}
.video-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.3s;
}
.video-card:hover .video-thumb img { transform: scale(1.05); }
.video-play-btn {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 48px;
  height: 48px;
  background: rgba(232,25,44,0.9);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: opacity 0.2s, transform 0.2s;
  z-index: 2;
}
.video-card:hover .video-play-btn { opacity: 1; }
.video-play-btn svg {
  fill: #fff;
  width: 18px;
  height: 18px;
  margin-left: 3px;
}
.video-badge {
  position: absolute;
  top: 8px;
  left: 8px;
  background: var(--brand-red);
  color: #fff;
  padding: 2px 8px;
  border-radius: 10px;
  font-size: 11px;
  font-weight: 700;
  z-index: 2;
}
.video-new-tag {
  background: #00a854;
}
.video-duration {
  position: absolute;
  bottom: 8px;
  right: 8px;
  background: rgba(0,0,0,0.7);
  color: #fff;
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 11px;
  z-index: 2;
}
.video-info { padding: 12px; }
.video-title {
  font-size: 14px;
  font-weight: 600;
  line-height: 1.4;
  margin-bottom: 8px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
  color: var(--text-primary);
}
.video-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}
.video-author {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  color: var(--text-muted);
}
.video-author-avatar {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  object-fit: cover;
  flex-shrink: 0;
}
.video-stats {
  display: flex;
  gap: 8px;
  font-size: 11px;
  color: var(--text-muted);
}

/* =============================================
   页面布局（主内容+侧边栏）
   ============================================= */
.page-layout {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 24px;
  align-items: start;
}

/* =============================================
   新闻列表
   ============================================= */
.news-list { display: flex; flex-direction: column; gap: 16px; }
.news-item {
  display: flex;
  gap: 16px;
  background: var(--bg-white);
  border-radius: var(--radius-md);
  padding: 16px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.2s;
}
.news-item:hover { box-shadow: var(--shadow-md); }
.news-thumb {
  flex-shrink: 0;
  width: 140px;
  height: 90px;
  border-radius: var(--radius-sm);
  overflow: hidden;
}
.news-thumb img { width: 100%; height: 100%; object-fit: cover; }
.news-content { flex: 1; }
.news-tag {
  display: inline-block;
  background: #fff0f1;
  color: var(--brand-red);
  padding: 2px 8px;
  border-radius: 10px;
  font-size: 11px;
  font-weight: 700;
  margin-bottom: 6px;
}
.news-title {
  font-size: 15px;
  font-weight: 700;
  line-height: 1.4;
  margin-bottom: 6px;
  color: var(--text-primary);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.news-title:hover { color: var(--brand-red); }
.news-desc {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 8px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.news-footer {
  display: flex;
  gap: 12px;
  font-size: 12px;
  color: var(--text-muted);
  flex-wrap: wrap;
}

/* =============================================
   侧边栏
   ============================================= */
.sidebar { display: flex; flex-direction: column; gap: 20px; }
.sidebar-widget {
  background: var(--bg-white);
  border-radius: var(--radius-md);
  padding: 16px;
  box-shadow: var(--shadow-sm);
}
.sidebar-widget-title {
  font-size: 15px;
  font-weight: 700;
  margin-bottom: 14px;
  padding-bottom: 10px;
  border-bottom: 2px solid #fff0f1;
  color: var(--text-primary);
}
.sidebar-list { display: flex; flex-direction: column; gap: 10px; }
.sidebar-list-item { display: flex; align-items: flex-start; gap: 8px; }
.sidebar-rank {
  flex-shrink: 0;
  width: 20px;
  height: 20px;
  background: #e8e8e8;
  color: #888;
  border-radius: 4px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 11px;
  font-weight: 700;
}
.sidebar-rank.top1 { background: var(--brand-red); color: #fff; }
.sidebar-rank.top2 { background: #ff6b35; color: #fff; }
.sidebar-rank.top3 { background: #ffa500; color: #fff; }
.sidebar-item-title {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.sidebar-item-title:hover { color: var(--brand-red); }

/* =============================================
   专题卡片
   ============================================= */
.topic-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.topic-card {
  background: var(--bg-white);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s, box-shadow 0.2s;
}
.topic-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); }
.topic-cover { position: relative; height: 160px; overflow: hidden; }
.topic-cover img { width: 100%; height: 100%; object-fit: cover; }
.topic-cover-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(to top, rgba(0,0,0,0.7) 0%, transparent 60%);
  display: flex;
  align-items: flex-end;
  padding: 12px;
}
.topic-cover-title { color: #fff; font-size: 16px; font-weight: 700; }
.topic-body { padding: 14px; }
.topic-desc {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 12px;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.topic-footer { display: flex; align-items: center; justify-content: space-between; }
.topic-count { font-size: 12px; color: var(--text-muted); }

/* =============================================
   作者卡片
   ============================================= */
.author-grid { display: grid; grid-template-columns: repeat(5, 1fr); gap: 16px; }
.author-card {
  background: var(--bg-white);
  border-radius: var(--radius-md);
  padding: 20px 12px;
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s, box-shadow 0.2s;
}
.author-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); }
.author-avatar {
  width: 72px;
  height: 72px;
  border-radius: 50%;
  object-fit: cover;
  margin: 0 auto 10px;
  border: 3px solid #fff0f1;
}
.author-name { font-size: 15px; font-weight: 700; margin-bottom: 6px; }
.author-tag {
  display: inline-block;
  background: #fff0f1;
  color: var(--brand-red);
  padding: 2px 10px;
  border-radius: 12px;
  font-size: 11px;
  font-weight: 700;
  margin-bottom: 10px;
}
.author-stats {
  display: flex;
  justify-content: center;
  gap: 12px;
  font-size: 12px;
  color: var(--text-muted);
  margin-bottom: 12px;
}
.author-follow-btn {
  width: 100%;
  padding: 7px 0;
  background: var(--brand-red);
  color: #fff;
  border: none;
  border-radius: 20px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  font-family: var(--font-main);
  transition: background 0.2s;
}
.author-follow-btn:hover { background: var(--brand-red-dark); }

/* =============================================
   互动专区
   ============================================= */
.interact-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.interact-card {
  background: var(--bg-white);
  border-radius: var(--radius-md);
  padding: 24px 16px;
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s;
}
.interact-card:hover { transform: translateY(-4px); }
.interact-icon { font-size: 36px; margin-bottom: 10px; }
.interact-title { font-size: 16px; font-weight: 700; margin-bottom: 8px; }
.interact-desc { font-size: 13px; color: var(--text-secondary); line-height: 1.5; margin-bottom: 16px; }
.interact-btn {
  padding: 8px 20px;
  background: var(--brand-red);
  color: #fff;
  border: none;
  border-radius: 20px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  font-family: var(--font-main);
  transition: background 0.2s;
}
.interact-btn:hover { background: var(--brand-red-dark); }

/* =============================================
   评价卡片
   ============================================= */
.reviews-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.review-card {
  background: var(--bg-white);
  border-radius: var(--radius-md);
  padding: 20px;
  box-shadow: var(--shadow-sm);
}
.review-header { display: flex; align-items: center; gap: 12px; margin-bottom: 12px; }
.review-avatar {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--brand-red);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
  font-weight: 700;
  flex-shrink: 0;
}
.review-username { font-size: 14px; font-weight: 700; margin-bottom: 4px; }
.review-stars { color: #ffa500; font-size: 14px; }
.review-text { font-size: 13px; color: var(--text-secondary); line-height: 1.7; margin-bottom: 12px; }
.review-footer { display: flex; align-items: center; justify-content: space-between; font-size: 12px; color: var(--text-muted); }
.review-like-btn {
  background: none;
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 2px 10px;
  font-size: 12px;
  cursor: pointer;
  font-family: var(--font-main);
  color: var(--text-muted);
  transition: all 0.2s;
}
.review-like-btn:hover { border-color: var(--brand-red); color: var(--brand-red); }

/* =============================================
   FAQ
   ============================================= */
.faq-list { display: flex; flex-direction: column; gap: 8px; }
.faq-item {
  background: var(--bg-white);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}
.faq-question {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
  user-select: none;
}
.faq-question:hover { background: #fff0f1; }
.faq-question.active { color: var(--brand-red); background: #fff0f1; }
.faq-icon {
  font-size: 20px;
  font-weight: 400;
  color: var(--brand-red);
  flex-shrink: 0;
  transition: transform 0.2s;
}
.faq-question.active .faq-icon { transform: rotate(45deg); }
.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.7;
}
.faq-answer.open {
  max-height: 400px;
  padding: 0 20px 16px;
}

/* =============================================
   帮助卡片
   ============================================= */
.help-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.help-card {
  background: var(--bg-white);
  border-radius: var(--radius-md);
  padding: 24px 16px;
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s, box-shadow 0.2s;
  display: block;
  color: var(--text-primary);
}
.help-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); color: var(--brand-red); }
.help-icon { font-size: 36px; margin-bottom: 10px; }
.help-title { font-size: 15px; font-weight: 700; margin-bottom: 8px; }
.help-desc { font-size: 12px; color: var(--text-muted); line-height: 1.5; }

/* =============================================
   按钮
   ============================================= */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 20px;
  border-radius: 20px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  font-family: var(--font-main);
  transition: all 0.2s;
  border: none;
  text-decoration: none;
}
.btn-primary {
  background: var(--brand-red);
  color: #fff;
}
.btn-primary:hover { background: var(--brand-red-dark); color: #fff; }
.btn-outline {
  background: transparent;
  color: var(--brand-red);
  border: 1px solid var(--brand-red);
}
.btn-outline:hover { background: var(--brand-red); color: #fff; }
.btn-sm { padding: 6px 14px; font-size: 13px; }

/* =============================================
   底部
   ============================================= */
.site-footer { background: #1a1a1a; color: #ccc; margin-top: 40px; }
.footer-main { padding: 40px 0 32px; }
.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 32px;
}
.footer-logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 22px;
  font-weight: 800;
  color: #fff;
  margin-bottom: 14px;
}
.footer-logo .logo-icon { color: var(--brand-red); }
.footer-desc { font-size: 13px; line-height: 1.7; color: #aaa; margin-bottom: 10px; }
.footer-domain-info { font-size: 12px; color: #888; margin-bottom: 6px; }
.footer-domain-val { color: #e8192c; font-weight: 600; }
.footer-update { font-size: 12px; color: #888; }
.footer-col-title {
  font-size: 14px;
  font-weight: 700;
  color: #fff;
  margin-bottom: 14px;
  padding-bottom: 8px;
  border-bottom: 1px solid #333;
}
.footer-links { display: flex; flex-direction: column; gap: 8px; }
.footer-links a { font-size: 13px; color: #aaa; transition: color 0.2s; }
.footer-links a:hover { color: var(--brand-red); }
.footer-bottom-brand {
  background: #111;
  padding: 16px 0;
  text-align: center;
}
.footer-bottom-logo {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 20px;
  font-weight: 800;
  color: #fff;
}
.footer-bottom-logo .logo-icon { color: var(--brand-red); }
.footer-copyright {
  background: #0d0d0d;
  padding: 14px 0;
  text-align: center;
  font-size: 12px;
  color: #666;
  line-height: 1.8;
}
.footer-copyright a { color: #888; }
.footer-copyright a:hover { color: var(--brand-red); }
.footer-disclaimer { font-size: 11px; color: #555; margin-top: 4px; }

/* =============================================
   移动端响应式
   ============================================= */
@media (max-width: 1024px) {
  .video-grid { grid-template-columns: repeat(3, 1fr); }
  .author-grid { grid-template-columns: repeat(3, 1fr); }
  .footer-grid { grid-template-columns: 1fr 1fr; gap: 24px; }
  .reviews-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
  .nav-toggle { display: block; }
  .nav-menu {
    display: none;
    position: absolute;
    top: 56px;
    left: 0;
    right: 0;
    background: #fff;
    flex-direction: column;
    padding: 8px 0;
    box-shadow: 0 4px 16px rgba(0,0,0,0.12);
    z-index: 200;
  }
  .nav-menu.open { display: flex; }
  .nav-item a { padding: 12px 20px; border-radius: 0; }
  .main-nav { position: relative; }

  .video-grid { grid-template-columns: repeat(2, 1fr); }
  .video-grid-3 { grid-template-columns: repeat(2, 1fr); }
  .topic-grid { grid-template-columns: repeat(2, 1fr); }
  .interact-grid { grid-template-columns: repeat(2, 1fr); }
  .help-grid { grid-template-columns: repeat(2, 1fr); }
  .author-grid { grid-template-columns: repeat(3, 1fr); }
  .reviews-grid { grid-template-columns: 1fr; }
  .page-layout { grid-template-columns: 1fr; }
  .hero-banner img { height: 220px; }
  .hero-title { font-size: 18px; }
  .hero-overlay { padding: 20px 20px 16px; }
  .footer-grid { grid-template-columns: 1fr; gap: 20px; }
  .news-item { flex-direction: column; }
  .news-thumb { width: 100%; height: 160px; }
  .top-bar-right { display: none; }
}

@media (max-width: 480px) {
  .video-grid { grid-template-columns: 1fr; }
  .video-grid-3 { grid-template-columns: 1fr; }
  .topic-grid { grid-template-columns: 1fr; }
  .author-grid { grid-template-columns: repeat(2, 1fr); }
  .interact-grid { grid-template-columns: repeat(2, 1fr); }
  .help-grid { grid-template-columns: repeat(2, 1fr); }
  .section-title { font-size: 18px; }
  .hero-banner img { height: 180px; }
}

/* =============================================
   回到顶部按钮
   ============================================= */
#backToTop {
  display: none;
  position: fixed;
  bottom: 32px;
  right: 24px;
  width: 44px;
  height: 44px;
  background: var(--brand-red);
  color: #fff;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  font-size: 20px;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 12px rgba(232,25,44,0.4);
  z-index: 999;
  transition: transform 0.2s, background 0.2s;
}
#backToTop:hover { transform: scale(1.1); background: var(--brand-red-dark); }