/* ===================================================
   17c 品牌官网 - 核心样式文件
   www.k3zj5dc.cn | 霓虹潮流·沉浸式科技娱乐风格
=================================================== */

/* CSS变量 */
:root {
  --pink: #ff2d78;
  --blue: #00d4ff;
  --purple: #8b5cf6;
  --dark: #0a0a1a;
  --white: #ffffff;
  --light-bg: #f8f9ff;
  --card-bg: rgba(255,255,255,0.95);
  --gradient-main: linear-gradient(135deg, #ff2d78 0%, #8b5cf6 50%, #00d4ff 100%);
  --gradient-soft: linear-gradient(135deg, #fff0f8 0%, #f0f8ff 100%);
  --shadow-neon-pink: 0 0 20px rgba(255,45,120,0.4);
  --shadow-neon-blue: 0 0 20px rgba(0,212,255,0.4);
  --shadow-card: 0 8px 32px rgba(139,92,246,0.15);
  --border-radius: 16px;
  --transition: all 0.3s cubic-bezier(0.4,0,0.2,1);
}

/* 重置与基础 */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; font-size: 16px; }
body {
  font-family: 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', '微软雅黑', sans-serif;
  background: var(--light-bg);
  color: #1a1a2e;
  line-height: 1.7;
  overflow-x: hidden;
}
a { text-decoration: none; color: inherit; transition: var(--transition); }
img { max-width: 100%; height: auto; display: block; }
ul { list-style: none; }

/* 粒子背景动画 */
@keyframes float {
  0%, 100% { transform: translateY(0px) rotate(0deg); }
  33% { transform: translateY(-15px) rotate(5deg); }
  66% { transform: translateY(8px) rotate(-3deg); }
}
@keyframes pulse-neon {
  0%, 100% { box-shadow: 0 0 10px rgba(255,45,120,0.5), 0 0 20px rgba(0,212,255,0.3); }
  50% { box-shadow: 0 0 25px rgba(255,45,120,0.8), 0 0 50px rgba(0,212,255,0.6); }
}
@keyframes shimmer {
  0% { background-position: -200% center; }
  100% { background-position: 200% center; }
}
@keyframes danmaku {
  0% { transform: translateX(100vw); opacity: 1; }
  100% { transform: translateX(-100%); opacity: 0.8; }
}
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes neon-border {
  0%, 100% { border-color: var(--pink); }
  50% { border-color: var(--blue); }
}

/* ===== 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(20px);
  border-bottom: 2px solid transparent;
  border-image: var(--gradient-main) 1;
  padding: 0 24px;
  height: 68px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  box-shadow: 0 2px 20px rgba(139,92,246,0.12);
}
.navbar-brand {
  font-size: 1.8rem;
  font-weight: 900;
  background: var(--gradient-main);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -1px;
}
.navbar-brand span { font-size: 0.75rem; font-weight: 400; display: block; color: #888; -webkit-text-fill-color: #888; }
.nav-menu {
  display: flex;
  align-items: center;
  gap: 4px;
}
.nav-menu a {
  padding: 8px 14px;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 600;
  color: #333;
  transition: var(--transition);
  white-space: nowrap;
}
.nav-menu a:hover, .nav-menu a.active {
  background: var(--gradient-main);
  color: white;
  transform: translateY(-1px);
}
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  padding: 8px;
}
.nav-toggle span {
  width: 24px; height: 2px;
  background: var(--gradient-main);
  border-radius: 2px;
  transition: var(--transition);
}

/* ===== 搜索框 ===== */
.search-bar-wrap {
  background: linear-gradient(135deg, #fff0f8 0%, #f0f8ff 100%);
  padding: 16px 24px;
  margin-top: 68px;
  border-bottom: 1px solid rgba(139,92,246,0.1);
}
.search-bar {
  max-width: 700px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  background: white;
  border-radius: 50px;
  border: 2px solid transparent;
  background-clip: padding-box;
  box-shadow: var(--shadow-card);
  overflow: hidden;
  position: relative;
}
.search-bar::before {
  content: '';
  position: absolute;
  inset: -2px;
  border-radius: 50px;
  background: var(--gradient-main);
  z-index: -1;
}
.search-bar input {
  flex: 1;
  border: none;
  outline: none;
  padding: 14px 20px;
  font-size: 0.95rem;
  background: transparent;
  color: #333;
}
.search-bar input::placeholder { color: #aaa; }
.search-btn {
  padding: 12px 28px;
  background: var(--gradient-main);
  color: white;
  border: none;
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 700;
  border-radius: 0 50px 50px 0;
  transition: var(--transition);
}
.search-btn:hover { opacity: 0.9; transform: scale(1.02); }
.search-hot-tags {
  text-align: center;
  margin-top: 10px;
  font-size: 0.82rem;
  color: #888;
}
.search-hot-tags a {
  display: inline-block;
  margin: 2px 4px;
  padding: 3px 10px;
  border-radius: 20px;
  background: rgba(255,45,120,0.08);
  color: var(--pink);
  font-weight: 600;
  transition: var(--transition);
}
.search-hot-tags a:hover { background: var(--pink); color: white; }

/* ===== Banner ===== */
.hero-banner {
  position: relative;
  min-height: 560px;
  display: flex;
  align-items: center;
  overflow: hidden;
  background: linear-gradient(135deg, #0a0a1a 0%, #1a0a2e 50%, #0a1a2e 100%);
}
.hero-banner .hero-bg {
  position: absolute;
  inset: 0;
  background-image: url('/assets/images/17c-banner-neon.jpg');
  background-size: cover;
  background-position: center;
  opacity: 0.4;
}
.hero-particles {
  position: absolute;
  inset: 0;
  overflow: hidden;
  pointer-events: none;
}
.particle {
  position: absolute;
  border-radius: 50%;
  animation: float 6s ease-in-out infinite;
}
.hero-content {
  position: relative;
  z-index: 2;
  max-width: 1200px;
  margin: 0 auto;
  padding: 60px 24px;
  animation: fadeInUp 0.8s ease;
}
.hero-badge {
  display: inline-block;
  padding: 6px 16px;
  border-radius: 20px;
  background: rgba(255,45,120,0.2);
  border: 1px solid rgba(255,45,120,0.5);
  color: #ff6ba8;
  font-size: 0.82rem;
  font-weight: 700;
  margin-bottom: 20px;
  animation: pulse-neon 2s infinite;
}
.hero-title {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 900;
  color: white;
  line-height: 1.2;
  margin-bottom: 16px;
}
.hero-title .gradient-text {
  background: var(--gradient-main);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero-subtitle {
  font-size: 1.1rem;
  color: rgba(255,255,255,0.75);
  margin-bottom: 32px;
  max-width: 600px;
}
.hero-btns { display: flex; gap: 16px; flex-wrap: wrap; }
.btn-primary {
  padding: 14px 32px;
  background: var(--gradient-main);
  color: white;
  border-radius: 50px;
  font-weight: 700;
  font-size: 1rem;
  border: none;
  cursor: pointer;
  transition: var(--transition);
  animation: pulse-neon 2s infinite;
  display: inline-flex;
  align-items: center;
  gap: 8px;
}
.btn-primary:hover { transform: translateY(-3px) scale(1.03); color: white; }
.btn-outline {
  padding: 14px 32px;
  background: transparent;
  color: white;
  border-radius: 50px;
  font-weight: 700;
  font-size: 1rem;
  border: 2px solid rgba(255,255,255,0.4);
  cursor: pointer;
  transition: var(--transition);
  display: inline-flex;
  align-items: center;
  gap: 8px;
}
.btn-outline:hover { border-color: var(--blue); color: var(--blue); transform: translateY(-3px); }
.hero-stats {
  display: flex;
  gap: 32px;
  margin-top: 40px;
  flex-wrap: wrap;
}
.hero-stat { text-align: center; }
.hero-stat .num { font-size: 1.8rem; font-weight: 900; background: var(--gradient-main); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.hero-stat .label { font-size: 0.78rem; color: rgba(255,255,255,0.6); }

/* ===== 弹幕 ===== */
.danmaku-bar {
  background: rgba(0,0,0,0.85);
  padding: 12px 0;
  overflow: hidden;
  position: relative;
  height: 44px;
}
.danmaku-track {
  display: flex;
  gap: 80px;
  white-space: nowrap;
  animation: danmaku 30s linear infinite;
}
.danmaku-item {
  font-size: 0.88rem;
  color: rgba(255,255,255,0.85);
  padding: 4px 12px;
  border-radius: 20px;
  background: rgba(255,45,120,0.15);
  border: 1px solid rgba(255,45,120,0.3);
}

/* ===== 通用区块 ===== */
.section { padding: 72px 24px; }
.section-alt { background: linear-gradient(135deg, #fff0f8 0%, #f0f8ff 100%); }
.container { max-width: 1200px; margin: 0 auto; }
.section-header { text-align: center; margin-bottom: 48px; }
.section-tag {
  display: inline-block;
  padding: 5px 16px;
  border-radius: 20px;
  background: var(--gradient-main);
  color: white;
  font-size: 0.78rem;
  font-weight: 700;
  margin-bottom: 12px;
  letter-spacing: 1px;
}
.section-title {
  font-size: clamp(1.6rem, 3vw, 2.4rem);
  font-weight: 900;
  color: #1a1a2e;
  margin-bottom: 12px;
}
.section-title .highlight {
  background: var(--gradient-main);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.section-desc { color: #666; font-size: 1rem; max-width: 600px; margin: 0 auto; }

/* ===== 视频卡片 ===== */
.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 24px;
}
.video-card {
  background: var(--card-bg);
  border-radius: var(--border-radius);
  overflow: hidden;
  box-shadow: var(--shadow-card);
  transition: var(--transition);
  cursor: pointer;
}
.video-card:hover {
  transform: translateY(-8px);
  box-shadow: 0 20px 60px rgba(139,92,246,0.25);
}
.video-thumb {
  position: relative;
  aspect-ratio: 16/9;
  overflow: hidden;
  background: #1a1a2e;
}
.video-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}
.video-card:hover .video-thumb img { transform: scale(1.08); }
.video-play-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(0,0,0,0);
  transition: var(--transition);
}
.video-card:hover .video-play-overlay { background: rgba(0,0,0,0.45); }
.play-btn-circle {
  width: 60px; height: 60px;
  border-radius: 50%;
  background: var(--gradient-main);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transform: scale(0.7);
  transition: var(--transition);
  box-shadow: 0 0 30px rgba(255,45,120,0.6);
}
.video-card:hover .play-btn-circle { opacity: 1; transform: scale(1); }
.play-btn-circle svg { width: 24px; height: 24px; fill: white; margin-left: 3px; }
.video-duration {
  position: absolute;
  bottom: 8px; right: 8px;
  background: rgba(0,0,0,0.75);
  color: white;
  font-size: 0.75rem;
  padding: 2px 8px;
  border-radius: 4px;
  font-weight: 600;
}
.video-quality {
  position: absolute;
  top: 8px; left: 8px;
  background: var(--gradient-main);
  color: white;
  font-size: 0.7rem;
  padding: 2px 8px;
  border-radius: 4px;
  font-weight: 700;
}
.video-info { padding: 16px; }
.video-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: #1a1a2e;
  margin-bottom: 10px;
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.video-meta {
  display: flex;
  gap: 16px;
  font-size: 0.78rem;
  color: #888;
}
.video-meta span { display: flex; align-items: center; gap: 4px; }
.video-tags { margin-top: 10px; display: flex; gap: 6px; flex-wrap: wrap; }
.video-tag {
  padding: 2px 10px;
  border-radius: 20px;
  background: rgba(255,45,120,0.08);
  color: var(--pink);
  font-size: 0.72rem;
  font-weight: 600;
}

/* ===== 社区模块 ===== */
.community-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
  align-items: start;
}
.topic-list { display: flex; flex-direction: column; gap: 12px; }
.topic-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  background: white;
  border-radius: 12px;
  border-left: 4px solid var(--pink);
  box-shadow: var(--shadow-card);
  transition: var(--transition);
}
.topic-item:hover { transform: translateX(6px); border-left-color: var(--blue); }
.topic-name { font-weight: 700; color: #1a1a2e; font-size: 0.95rem; }
.topic-hot { font-size: 0.8rem; color: var(--pink); font-weight: 700; }
.danmaku-box {
  background: #0a0a1a;
  border-radius: var(--border-radius);
  padding: 20px;
  min-height: 200px;
  overflow: hidden;
  position: relative;
}
.danmaku-box-title { color: rgba(255,255,255,0.6); font-size: 0.82rem; margin-bottom: 16px; }
.danmaku-stream { display: flex; flex-direction: column; gap: 10px; }
.danmaku-msg {
  color: rgba(255,255,255,0.85);
  font-size: 0.88rem;
  padding: 8px 14px;
  border-radius: 20px;
  background: rgba(255,45,120,0.12);
  border: 1px solid rgba(255,45,120,0.25);
  animation: fadeInUp 0.5s ease;
}

/* ===== AI模块 ===== */
.ai-tools-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 24px;
}
.ai-tool-card {
  background: white;
  border-radius: var(--border-radius);
  padding: 28px;
  box-shadow: var(--shadow-card);
  border: 2px solid transparent;
  transition: var(--transition);
  position: relative;
  overflow: hidden;
}
.ai-tool-card::before {
  content: '';
  position: absolute;
  inset: -2px;
  border-radius: var(--border-radius);
  background: var(--gradient-main);
  z-index: -1;
  opacity: 0;
  transition: var(--transition);
}
.ai-tool-card:hover::before { opacity: 1; }
.ai-tool-card:hover { transform: translateY(-6px); }
.ai-tool-icon {
  width: 56px; height: 56px;
  border-radius: 14px;
  background: var(--gradient-main);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 16px;
  font-size: 1.6rem;
}
.ai-tool-name { font-size: 1.1rem; font-weight: 800; color: #1a1a2e; margin-bottom: 8px; }
.ai-tool-desc { font-size: 0.88rem; color: #666; line-height: 1.6; }
.ai-tool-btn {
  margin-top: 16px;
  padding: 8px 20px;
  border-radius: 20px;
  background: var(--gradient-main);
  color: white;
  font-size: 0.82rem;
  font-weight: 700;
  display: inline-block;
  transition: var(--transition);
}
.ai-tool-btn:hover { transform: scale(1.05); color: white; }

/* ===== 专家模块 ===== */
.experts-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 28px;
}
.expert-card {
  background: white;
  border-radius: var(--border-radius);
  padding: 32px 24px;
  text-align: center;
  box-shadow: var(--shadow-card);
  transition: var(--transition);
}
.expert-card:hover { transform: translateY(-8px); box-shadow: 0 20px 60px rgba(255,45,120,0.2); }
.expert-avatar {
  width: 100px; height: 100px;
  border-radius: 50%;
  margin: 0 auto 16px;
  object-fit: cover;
  border: 4px solid transparent;
  background: var(--gradient-main);
  padding: 3px;
}
.expert-avatar-inner {
  width: 100%;
  height: 100%;
  border-radius: 50%;
  object-fit: cover;
  display: block;
}
.expert-name { font-size: 1.1rem; font-weight: 800; color: #1a1a2e; margin-bottom: 6px; }
.expert-role { font-size: 0.85rem; color: var(--pink); font-weight: 600; margin-bottom: 12px; }
.expert-desc { font-size: 0.82rem; color: #666; line-height: 1.6; }

/* ===== 评价模块 ===== */
.reviews-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 24px;
}
.review-card {
  background: white;
  border-radius: var(--border-radius);
  padding: 24px;
  box-shadow: var(--shadow-card);
  transition: var(--transition);
  position: relative;
}
.review-card::before {
  content: '"';
  position: absolute;
  top: 12px; right: 20px;
  font-size: 4rem;
  color: rgba(255,45,120,0.1);
  font-family: Georgia, serif;
  line-height: 1;
}
.review-card:hover { transform: translateY(-4px); }
.review-header { display: flex; align-items: center; gap: 12px; margin-bottom: 16px; }
.review-avatar {
  width: 48px; height: 48px;
  border-radius: 50%;
  object-fit: cover;
  border: 2px solid var(--pink);
}
.review-user { font-weight: 700; color: #1a1a2e; font-size: 0.95rem; }
.review-stars { color: #ffd700; font-size: 0.85rem; }
.review-text { font-size: 0.88rem; color: #555; line-height: 1.7; }

/* ===== FAQ ===== */
.faq-list { max-width: 800px; margin: 0 auto; display: flex; flex-direction: column; gap: 12px; }
.faq-item {
  background: white;
  border-radius: 12px;
  box-shadow: var(--shadow-card);
  overflow: hidden;
}
.faq-question {
  padding: 18px 24px;
  font-weight: 700;
  color: #1a1a2e;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: var(--transition);
  font-size: 0.95rem;
}
.faq-question:hover { color: var(--pink); }
.faq-question .icon {
  width: 24px; height: 24px;
  border-radius: 50%;
  background: var(--gradient-main);
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  flex-shrink: 0;
  transition: var(--transition);
}
.faq-item.open .faq-question .icon { transform: rotate(45deg); }
.faq-answer {
  padding: 0 24px;
  max-height: 0;
  overflow: hidden;
  transition: all 0.4s ease;
  font-size: 0.88rem;
  color: #666;
  line-height: 1.7;
}
.faq-item.open .faq-answer { max-height: 200px; padding: 0 24px 18px; }

/* ===== 合作伙伴 ===== */
.partners-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 20px;
  margin-bottom: 48px;
}
.partner-item {
  background: white;
  border-radius: 12px;
  padding: 20px;
  text-align: center;
  box-shadow: var(--shadow-card);
  font-weight: 800;
  font-size: 1rem;
  color: #888;
  transition: var(--transition);
}
.partner-item:hover { color: var(--pink); transform: scale(1.05); box-shadow: var(--shadow-neon-pink); }

/* ===== 联系模块 ===== */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  align-items: center;
}
.contact-info { display: flex; flex-direction: column; gap: 20px; }
.contact-item { display: flex; align-items: flex-start; gap: 14px; }
.contact-icon {
  width: 44px; height: 44px;
  border-radius: 12px;
  background: var(--gradient-main);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  flex-shrink: 0;
}
.contact-label { font-size: 0.78rem; color: #888; margin-bottom: 2px; }
.contact-value { font-weight: 700; color: #1a1a2e; }
.qr-group { display: flex; gap: 24px; }
.qr-item { text-align: center; }
.qr-placeholder {
  width: 120px; height: 120px;
  border-radius: 12px;
  background: var(--gradient-main);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 0.75rem;
  font-weight: 700;
  margin: 0 auto 8px;
  text-align: center;
  padding: 8px;
}
.qr-label { font-size: 0.8rem; color: #888; }

/* ===== 页脚 ===== */
.footer {
  background: #0a0a1a;
  color: rgba(255,255,255,0.75);
  padding: 48px 24px 24px;
}
.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  max-width: 1200px;
  margin: 0 auto 40px;
}
.footer-brand { font-size: 2rem; font-weight: 900; background: var(--gradient-main); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; margin-bottom: 12px; }
.footer-desc { font-size: 0.85rem; line-height: 1.7; color: rgba(255,255,255,0.5); }
.footer-col-title { font-size: 0.95rem; font-weight: 700; color: white; margin-bottom: 16px; }
.footer-links { display: flex; flex-direction: column; gap: 8px; }
.footer-links a { font-size: 0.85rem; color: rgba(255,255,255,0.5); transition: var(--transition); }
.footer-links a:hover { color: var(--pink); }
.footer-bottom {
  max-width: 1200px;
  margin: 0 auto;
  padding-top: 24px;
  border-top: 1px solid rgba(255,255,255,0.08);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
  font-size: 0.8rem;
  color: rgba(255,255,255,0.4);
}
.footer-bottom a { color: rgba(255,255,255,0.4); }
.footer-bottom a:hover { color: var(--pink); }
.social-links { display: flex; gap: 12px; }
.social-link {
  width: 36px; height: 36px;
  border-radius: 50%;
  background: rgba(255,255,255,0.08);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.85rem;
  transition: var(--transition);
}
.social-link:hover { background: var(--gradient-main); color: white; }

/* ===== 面包屑 ===== */
.breadcrumb {
  padding: 12px 24px;
  background: white;
  border-bottom: 1px solid rgba(139,92,246,0.1);
  font-size: 0.82rem;
  color: #888;
}
.breadcrumb a { color: var(--pink); }
.breadcrumb a:hover { text-decoration: underline; }
.breadcrumb span { margin: 0 6px; }

/* ===== 内页Banner ===== */
.inner-hero {
  background: linear-gradient(135deg, #0a0a1a 0%, #1a0a2e 50%, #0a1a2e 100%);
  padding: 80px 24px 60px;
  text-align: center;
  position: relative;
  overflow: hidden;
}
.inner-hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background: url('/assets/images/17c-banner-neon.jpg') center/cover;
  opacity: 0.15;
}
.inner-hero-content { position: relative; z-index: 1; }
.inner-hero h1 { font-size: clamp(1.8rem, 4vw, 3rem); font-weight: 900; color: white; margin-bottom: 12px; }
.inner-hero p { color: rgba(255,255,255,0.7); font-size: 1rem; max-width: 600px; margin: 0 auto; }

/* ===== 响应式 ===== */
@media (max-width: 1024px) {
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .community-grid { grid-template-columns: 1fr; }
  .contact-grid { grid-template-columns: 1fr; }
}
@media (max-width: 768px) {
  .nav-menu { display: none; flex-direction: column; position: fixed; top: 68px; left: 0; right: 0; background: white; padding: 16px; box-shadow: 0 10px 30px rgba(0,0,0,0.1); gap: 4px; }
  .nav-menu.open { display: flex; }
  .nav-toggle { display: flex; }
  .hero-banner { min-height: 480px; }
  .hero-stats { gap: 20px; }
  .footer-grid { grid-template-columns: 1fr; gap: 24px; }
  .footer-bottom { flex-direction: column; text-align: center; }
  .video-grid { grid-template-columns: 1fr 1fr; }
  .experts-grid { grid-template-columns: 1fr 1fr; }
  .reviews-grid { grid-template-columns: 1fr; }
}
@media (max-width: 480px) {
  .video-grid { grid-template-columns: 1fr; }
  .experts-grid { grid-template-columns: 1fr; }
  .hero-btns { flex-direction: column; }
  .partners-grid { grid-template-columns: repeat(3, 1fr); }
}

/* ===== 工具类 ===== */
.text-center { text-align: center; }
.mt-8 { margin-top: 8px; }
.mt-16 { margin-top: 16px; }
.mt-24 { margin-top: 24px; }
.mt-32 { margin-top: 32px; }
.mb-24 { margin-bottom: 24px; }
.flex { display: flex; }
.flex-center { display: flex; align-items: center; justify-content: center; }
.gap-16 { gap: 16px; }
.hidden { display: none !important; }
.loading-shimmer {
  background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
}