/* ============================================
   51视频 - 原创样式表
   品牌色系：活力橙 + 深夜蓝 + 玫瑰红
   ============================================ */

/* CSS Reset & Base */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

:root {
  --primary: #FF6B35;
  --secondary: #1A1A2E;
  --accent: #E94560;
  --bg-dark: #0F0F23;
  --bg-card: #16162A;
  --bg-card-hover: #1E1E3A;
  --text-light: #EAEAEA;
  --text-muted: #A0A0B8;
  --text-white: #FFFFFF;
  --gradient-main: linear-gradient(135deg, #FF6B35, #E94560);
  --gradient-dark: linear-gradient(180deg, #0F0F23, #1A1A2E);
  --shadow-card: 0 4px 24px rgba(0,0,0,0.3);
  --shadow-hover: 0 8px 32px rgba(255,107,53,0.2);
  --radius: 12px;
  --radius-sm: 8px;
  --transition: all 0.3s ease;
}

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

body {
  font-family: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  background: var(--bg-dark);
  color: var(--text-light);
  line-height: 1.7;
  overflow-x: hidden;
}

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

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

.container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }

/* ============================================
   Header & Navigation
   ============================================ */
.site-header {
  position: fixed; top: 0; left: 0; right: 0; z-index: 1000;
  background: rgba(15,15,35,0.95);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(255,107,53,0.15);
  padding: 0 20px;
}

.header-inner {
  max-width: 1200px; margin: 0 auto;
  display: flex; align-items: center; justify-content: space-between;
  height: 68px;
}

.logo { display: flex; align-items: center; gap: 10px; }
.logo img { height: 42px; width: auto; }
.logo-text { font-size: 1.4rem; font-weight: 700; color: var(--primary); letter-spacing: 1px; }

.main-nav { display: flex; align-items: center; gap: 0; }
.main-nav a {
  color: var(--text-light); padding: 8px 16px; font-size: 0.95rem;
  border-radius: var(--radius-sm); transition: var(--transition); position: relative;
}
.main-nav a:hover, .main-nav a.active {
  color: var(--primary); background: rgba(255,107,53,0.1);
}

.mobile-menu-btn {
  display: none; background: none; border: none; color: var(--text-light);
  font-size: 1.5rem; cursor: pointer;
}

/* Search Bar */
.search-bar {
  max-width: 1200px; margin: 0 auto; padding: 12px 20px;
  background: rgba(22,22,42,0.8);
  border-bottom: 1px solid rgba(255,107,53,0.08);
}

.search-wrapper {
  display: flex; align-items: center; gap: 10px;
  max-width: 600px; margin: 0 auto;
}

.search-wrapper input {
  flex: 1; padding: 10px 18px; border: 2px solid rgba(255,107,53,0.3);
  border-radius: 24px; background: var(--bg-card); color: var(--text-light);
  font-size: 0.9rem; outline: none; transition: var(--transition);
}
.search-wrapper input:focus { border-color: var(--primary); box-shadow: 0 0 12px rgba(255,107,53,0.2); }
.search-wrapper input::placeholder { color: var(--text-muted); }

.search-wrapper button {
  padding: 10px 24px; background: var(--gradient-main); color: #fff;
  border: none; border-radius: 24px; cursor: pointer; font-size: 0.9rem;
  font-weight: 600; transition: var(--transition);
}
.search-wrapper button:hover { transform: scale(1.05); box-shadow: 0 4px 16px rgba(255,107,53,0.4); }

/* ============================================
   Hero Section
   ============================================ */
.hero {
  margin-top: 68px; position: relative; overflow: hidden;
  min-height: 520px; display: flex; align-items: center;
}

.hero-bg {
  position: absolute; inset: 0; z-index: 0;
}
.hero-bg img {
  width: 100%; height: 100%; object-fit: cover;
  filter: brightness(0.45);
}

.hero-content {
  position: relative; z-index: 2; max-width: 1200px;
  margin: 0 auto; padding: 80px 20px; text-align: center;
}

.hero h1 {
  font-size: 2.8rem; font-weight: 800; margin-bottom: 16px;
  background: var(--gradient-main); -webkit-background-clip: text;
  -webkit-text-fill-color: transparent; background-clip: text;
  line-height: 1.3;
}

.hero h2 {
  font-size: 1.3rem; color: var(--text-muted); font-weight: 400;
  margin-bottom: 32px; max-width: 640px; margin-left: auto; margin-right: auto;
}

.hero-tags { display: flex; flex-wrap: wrap; justify-content: center; gap: 10px; margin-bottom: 32px; }
.hero-tags span {
  padding: 6px 16px; background: rgba(255,107,53,0.15); color: var(--primary);
  border-radius: 20px; font-size: 0.85rem; border: 1px solid rgba(255,107,53,0.3);
}

.btn-primary {
  display: inline-block; padding: 14px 36px; background: var(--gradient-main);
  color: #fff; border-radius: 28px; font-size: 1rem; font-weight: 600;
  transition: var(--transition); border: none; cursor: pointer;
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: var(--shadow-hover); color: #fff; }

.btn-outline {
  display: inline-block; padding: 12px 32px;
  border: 2px solid var(--primary); color: var(--primary);
  border-radius: 28px; font-size: 0.95rem; font-weight: 600;
  transition: var(--transition); background: transparent;
}
.btn-outline:hover { background: var(--primary); color: #fff; }

/* ============================================
   Section Common
   ============================================ */
.section { padding: 72px 0; }
.section-dark { background: var(--bg-dark); }
.section-alt { background: var(--secondary); }

.section-header { text-align: center; margin-bottom: 48px; }
.section-header h2 {
  font-size: 2rem; font-weight: 700; margin-bottom: 12px;
  color: var(--text-white);
}
.section-header h2 span { color: var(--primary); }
.section-header p { color: var(--text-muted); font-size: 1rem; max-width: 600px; margin: 0 auto; }

.section-label {
  display: inline-block; padding: 4px 14px; background: rgba(255,107,53,0.12);
  color: var(--primary); border-radius: 16px; font-size: 0.8rem; font-weight: 600;
  margin-bottom: 12px; letter-spacing: 1px;
}

/* ============================================
   Video Card Grid
   ============================================ */
.video-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 24px;
}

.video-card {
  background: var(--bg-card); border-radius: var(--radius);
  overflow: hidden; transition: var(--transition);
  box-shadow: var(--shadow-card); cursor: pointer;
}
.video-card:hover { transform: translateY(-6px); box-shadow: var(--shadow-hover); background: var(--bg-card-hover); }

.video-thumb {
  position: relative; padding-top: 56.25%; overflow: hidden;
}
.video-thumb img {
  position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover;
  transition: transform 0.4s ease;
}
.video-card:hover .video-thumb img { transform: scale(1.08); }

.play-btn {
  position: absolute; top: 50%; left: 50%; transform: translate(-50%, -50%);
  width: 56px; height: 56px; background: rgba(255,107,53,0.9);
  border-radius: 50%; display: flex; align-items: center; justify-content: center;
  opacity: 0; transition: var(--transition); z-index: 2;
}
.play-btn::after {
  content: ''; width: 0; height: 0;
  border-left: 18px solid #fff; border-top: 11px solid transparent;
  border-bottom: 11px solid transparent; margin-left: 4px;
}
.video-card:hover .play-btn { opacity: 1; }

.video-duration {
  position: absolute; bottom: 8px; right: 8px;
  background: rgba(0,0,0,0.75); color: #fff; padding: 2px 8px;
  border-radius: 4px; font-size: 0.75rem;
}

.video-info { padding: 14px 16px; }
.video-info h3 {
  font-size: 0.95rem; font-weight: 600; color: var(--text-white);
  margin-bottom: 8px; line-height: 1.4;
  display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden;
}

.video-meta {
  display: flex; align-items: center; gap: 12px;
  font-size: 0.8rem; color: var(--text-muted);
}
.video-meta span { display: flex; align-items: center; gap: 4px; }

.video-tags { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 8px; }
.video-tags span {
  padding: 2px 10px; background: rgba(255,107,53,0.1); color: var(--primary);
  border-radius: 12px; font-size: 0.72rem;
}

/* ============================================
   Service Grid
   ============================================ */
.service-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 24px;
}

.service-card {
  background: var(--bg-card); border-radius: var(--radius); padding: 32px 24px;
  text-align: center; transition: var(--transition); border: 1px solid transparent;
}
.service-card:hover { border-color: var(--primary); transform: translateY(-4px); box-shadow: var(--shadow-hover); }

.service-icon {
  width: 64px; height: 64px; margin: 0 auto 18px;
  background: var(--gradient-main); border-radius: 16px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.8rem;
}

.service-card h3 { font-size: 1.1rem; color: var(--text-white); margin-bottom: 10px; }
.service-card p { font-size: 0.88rem; color: var(--text-muted); line-height: 1.6; }

/* ============================================
   AI Feature Section
   ============================================ */
.ai-feature-wrap {
  display: grid; grid-template-columns: 1fr 1fr; gap: 40px; align-items: center;
}

.ai-feature-img { border-radius: var(--radius); overflow: hidden; }
.ai-feature-img img { width: 100%; border-radius: var(--radius); }

.ai-feature-list { list-style: none; }
.ai-feature-list li {
  padding: 16px 0; border-bottom: 1px solid rgba(255,107,53,0.1);
  display: flex; align-items: flex-start; gap: 14px;
}
.ai-feature-list li:last-child { border-bottom: none; }

.ai-dot {
  width: 10px; height: 10px; background: var(--primary); border-radius: 50%;
  margin-top: 7px; flex-shrink: 0;
}

.ai-feature-list h4 { font-size: 1rem; color: var(--text-white); margin-bottom: 4px; }
.ai-feature-list p { font-size: 0.85rem; color: var(--text-muted); }

/* ============================================
   Expert Team
   ============================================ */
.expert-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 24px;
}

.expert-card {
  background: var(--bg-card); border-radius: var(--radius); padding: 28px 20px;
  text-align: center; transition: var(--transition);
}
.expert-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); }

.expert-avatar {
  width: 96px; height: 96px; border-radius: 50%; margin: 0 auto 16px;
  overflow: hidden; border: 3px solid var(--primary);
}
.expert-avatar img { width: 100%; height: 100%; object-fit: cover; }

.expert-card h3 { font-size: 1.05rem; color: var(--text-white); margin-bottom: 4px; }
.expert-card .expert-title { font-size: 0.85rem; color: var(--primary); margin-bottom: 10px; }
.expert-card p { font-size: 0.82rem; color: var(--text-muted); margin-bottom: 14px; line-height: 1.5; }

.expert-btns { display: flex; justify-content: center; gap: 10px; }
.expert-btns a {
  padding: 6px 16px; border-radius: 16px; font-size: 0.8rem; font-weight: 600;
}
.expert-btns .btn-sm-primary { background: var(--primary); color: #fff; }
.expert-btns .btn-sm-outline { border: 1px solid var(--primary); color: var(--primary); }
.expert-btns .btn-sm-outline:hover { background: var(--primary); color: #fff; }

/* ============================================
   Brand Partners
   ============================================ */
.brand-wall {
  display: flex; flex-wrap: wrap; justify-content: center; gap: 32px;
  align-items: center; padding: 24px 0;
}
.brand-wall .brand-item {
  padding: 16px 28px; background: var(--bg-card); border-radius: var(--radius-sm);
  font-size: 1rem; color: var(--text-muted); font-weight: 600;
  border: 1px solid rgba(255,107,53,0.1); transition: var(--transition);
}
.brand-wall .brand-item:hover { border-color: var(--primary); color: var(--primary); }

/* ============================================
   Reviews
   ============================================ */
.review-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 24px;
}

.review-card {
  background: var(--bg-card); border-radius: var(--radius); padding: 24px;
  border-left: 3px solid var(--primary);
}

.review-stars { color: #FFB800; font-size: 0.9rem; margin-bottom: 10px; letter-spacing: 2px; }
.review-card p { font-size: 0.9rem; color: var(--text-light); margin-bottom: 14px; line-height: 1.6; font-style: italic; }
.review-author { font-size: 0.82rem; color: var(--text-muted); }
.review-author strong { color: var(--primary); }

/* ============================================
   FAQ
   ============================================ */
.faq-list { max-width: 800px; margin: 0 auto; }

.faq-item {
  background: var(--bg-card); border-radius: var(--radius-sm);
  margin-bottom: 12px; overflow: hidden;
}

.faq-question {
  padding: 18px 24px; cursor: pointer; display: flex;
  justify-content: space-between; align-items: center;
  font-weight: 600; color: var(--text-white); font-size: 0.95rem;
  transition: var(--transition);
}
.faq-question:hover { color: var(--primary); }
.faq-question .faq-icon { font-size: 1.2rem; transition: transform 0.3s; color: var(--primary); }
.faq-item.active .faq-icon { transform: rotate(45deg); }

.faq-answer {
  max-height: 0; overflow: hidden; transition: max-height 0.3s ease;
  padding: 0 24px;
}
.faq-item.active .faq-answer { max-height: 300px; padding: 0 24px 18px; }
.faq-answer p { font-size: 0.88rem; color: var(--text-muted); line-height: 1.7; }

/* ============================================
   Contact Section
   ============================================ */
.contact-grid {
  display: grid; grid-template-columns: 1fr 1fr; gap: 40px;
}

.contact-info-list { list-style: none; }
.contact-info-list li {
  padding: 14px 0; border-bottom: 1px solid rgba(255,107,53,0.1);
  display: flex; align-items: center; gap: 14px;
  font-size: 0.92rem; color: var(--text-light);
}
.contact-info-list li strong { color: var(--primary); min-width: 80px; }

.contact-qr {
  display: flex; gap: 24px; justify-content: center; align-items: flex-start;
}
.contact-qr .qr-item { text-align: center; }
.contact-qr .qr-item img { width: 160px; height: 160px; border-radius: var(--radius-sm); margin-bottom: 8px; }
.contact-qr .qr-item p { font-size: 0.82rem; color: var(--text-muted); }

/* ============================================
   Social Share
   ============================================ */
.share-bar {
  display: flex; justify-content: center; gap: 16px; padding: 24px 0;
}
.share-bar a {
  width: 44px; height: 44px; border-radius: 50%;
  background: var(--bg-card); display: flex; align-items: center;
  justify-content: center; color: var(--text-muted); font-size: 1.1rem;
  transition: var(--transition); border: 1px solid rgba(255,107,53,0.15);
}
.share-bar a:hover { background: var(--primary); color: #fff; border-color: var(--primary); }

/* ============================================
   Footer
   ============================================ */
.site-footer {
  background: #0A0A1A; border-top: 1px solid rgba(255,107,53,0.1);
  padding: 48px 0 24px;
}

.footer-grid {
  display: grid; grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 32px; margin-bottom: 32px;
}

.footer-brand .logo-text { font-size: 1.3rem; margin-bottom: 12px; display: block; }
.footer-brand p { font-size: 0.85rem; color: var(--text-muted); line-height: 1.6; }

.footer-links h4 {
  font-size: 0.95rem; color: var(--text-white); margin-bottom: 16px;
  padding-bottom: 8px; border-bottom: 2px solid var(--primary); display: inline-block;
}
.footer-links ul { list-style: none; }
.footer-links li { margin-bottom: 8px; }
.footer-links a { color: var(--text-muted); font-size: 0.85rem; }
.footer-links a:hover { color: var(--primary); }

.footer-bottom {
  text-align: center; padding-top: 24px;
  border-top: 1px solid rgba(255,255,255,0.05);
  font-size: 0.82rem; color: var(--text-muted);
}
.footer-bottom a { color: var(--primary); }

/* ============================================
   Breadcrumb
   ============================================ */
.breadcrumb {
  padding: 14px 0; font-size: 0.85rem; color: var(--text-muted);
  margin-top: 68px;
}
.breadcrumb a { color: var(--primary); }
.breadcrumb span { margin: 0 8px; }

/* ============================================
   How-To Guide
   ============================================ */
.howto-steps {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 24px; counter-reset: step;
}

.howto-step {
  background: var(--bg-card); border-radius: var(--radius); padding: 28px 20px;
  text-align: center; position: relative; counter-increment: step;
}
.howto-step::before {
  content: counter(step); position: absolute; top: -14px; left: 50%;
  transform: translateX(-50%); width: 32px; height: 32px;
  background: var(--gradient-main); border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  color: #fff; font-weight: 700; font-size: 0.9rem;
}
.howto-step h4 { font-size: 1rem; color: var(--text-white); margin-bottom: 8px; margin-top: 8px; }
.howto-step p { font-size: 0.85rem; color: var(--text-muted); }

/* ============================================
   Community Feature Cards
   ============================================ */
.community-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 20px;
}

.community-card {
  background: var(--bg-card); border-radius: var(--radius); padding: 24px 16px;
  text-align: center; transition: var(--transition);
  border: 1px solid transparent;
}
.community-card:hover { border-color: var(--accent); transform: translateY(-3px); }

.community-card .icon { font-size: 2rem; margin-bottom: 12px; }
.community-card h4 { font-size: 0.95rem; color: var(--text-white); margin-bottom: 6px; }
.community-card p { font-size: 0.8rem; color: var(--text-muted); }

/* ============================================
   Inner Page Content
   ============================================ */
.page-hero {
  margin-top: 68px; padding: 60px 0; text-align: center;
  background: var(--gradient-dark); position: relative;
}
.page-hero h1 { font-size: 2.2rem; font-weight: 700; color: var(--text-white); margin-bottom: 12px; }
.page-hero p { font-size: 1rem; color: var(--text-muted); max-width: 600px; margin: 0 auto; }

.content-section { padding: 48px 0; }
.content-section h2 { font-size: 1.6rem; color: var(--text-white); margin-bottom: 20px; }
.content-section h3 { font-size: 1.2rem; color: var(--primary); margin-bottom: 12px; }
.content-section p { font-size: 0.92rem; color: var(--text-light); margin-bottom: 16px; line-height: 1.8; }

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 1024px) {
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .ai-feature-wrap { grid-template-columns: 1fr; }
  .contact-grid { grid-template-columns: 1fr; }
}

@media (max-width: 768px) {
  .main-nav { display: none; }
  .main-nav.active {
    display: flex; flex-direction: column; position: absolute;
    top: 68px; left: 0; right: 0; background: rgba(15,15,35,0.98);
    padding: 16px; gap: 4px; border-bottom: 1px solid rgba(255,107,53,0.2);
  }
  .mobile-menu-btn { display: block; }

  .hero h1 { font-size: 1.8rem; }
  .hero h2 { font-size: 1rem; }
  .hero { min-height: 400px; }

  .section { padding: 48px 0; }
  .section-header h2 { font-size: 1.5rem; }

  .video-grid { grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); }
  .service-grid { grid-template-columns: 1fr 1fr; }
  .expert-grid { grid-template-columns: 1fr 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
  .howto-steps { grid-template-columns: 1fr 1fr; }

  .contact-qr { flex-direction: column; align-items: center; }
}

@media (max-width: 480px) {
  .service-grid { grid-template-columns: 1fr; }
  .expert-grid { grid-template-columns: 1fr; }
  .video-grid { grid-template-columns: 1fr; }
  .howto-steps { grid-template-columns: 1fr; }
  .community-grid { grid-template-columns: 1fr 1fr; }
  .hero-content { padding: 40px 16px; }
  .hero h1 { font-size: 1.5rem; }
}

/* ============================================
   Lazy Load & Animation
   ============================================ */
.lazy { opacity: 0; transition: opacity 0.5s ease; }
.lazy.loaded { opacity: 1; }

.fade-in {
  opacity: 0; transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.fade-in.visible { opacity: 1; transform: translateY(0); }

/* ============================================
   Scrollbar
   ============================================ */
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--bg-dark); }
::-webkit-scrollbar-thumb { background: var(--primary); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--accent); }

/* ============================================
   Additional Styles (Supplement)
   ============================================ */
.howto-step h5 { font-size: 1rem; color: var(--text-white); margin-bottom: 8px; margin-top: 8px; }
.community-card h5 { font-size: 0.95rem; color: var(--text-white); margin-bottom: 8px; }

/* Page Hero for inner pages */
.page-hero {
  text-align: center;
  padding: 48px 20px 36px;
  background: var(--gradient-dark);
}
.page-hero h1 {
  font-size: 1.8rem;
  color: var(--text-white);
  margin-bottom: 12px;
}
.page-hero p {
  color: var(--text-muted);
  font-size: 1rem;
}