/* roulang page: index */
/* ---- CSS Custom Properties & Design System ---- */
    :root {
      --primary: #E8451E;
      --primary-deep: #C0392B;
      --primary-soft: #FFF0EC;
      --accent-gold: #FFB800;
      --dark-bg: #1A1A2E;
      --dark-bg-alt: #16213E;
      --surface: #FFFFFF;
      --bg-warm: #FBF9F6;
      --bg-light-gray: #F5F2ED;
      --text-primary: #1E1E24;
      --text-secondary: #5C5C66;
      --text-on-dark: #FFFFFF;
      --text-muted-on-dark: #AAAAAA;
      --border-light: #F0EDE8;
      --border-medium: #E8E5DF;
      --success-green: #2E7D32;
      
      --font-sans: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", system-ui, -apple-system, sans-serif;
      --font-mono: "Inter", "SF Pro Display", system-ui, sans-serif;
      
      --radius-card: 12px;
      --radius-btn: 8px;
      --radius-badge: 6px;
      
      --shadow-sm: 0 1px 3px rgba(0,0,0,0.06), 0 4px 16px rgba(0,0,0,0.04);
      --shadow-hover: 0 8px 30px rgba(232,69,30,0.12);
      
      --spacing-section: 100px;
      --spacing-element: 24px;
      --max-width: 1200px;
      
      --transition-smooth: 0.3s ease;
    }
    
    /* ---- Reset & Base ---- */
    *, *::before, *::after {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    
    html {
      scroll-behavior: smooth;
      -webkit-font-smoothing: antialiased;
      -moz-osx-font-smoothing: grayscale;
    }
    
    body {
      font-family: var(--font-sans);
      font-size: 16px;
      line-height: 1.75;
      color: var(--text-primary);
      background-color: var(--bg-warm);
      overflow-x: hidden;
    }
    
    img {
      max-width: 100%;
      height: auto;
      display: block;
    }
    
    a {
      text-decoration: none;
      color: inherit;
    }
    
    button {
      font-family: inherit;
      cursor: pointer;
      border: none;
      background: none;
    }
    
    .container {
      max-width: var(--max-width);
      margin-left: auto;
      margin-right: auto;
      padding-left: 24px;
      padding-right: 24px;
    }
    
    /* ---- Typography ---- */
    h1, h2, h3, h4 {
      font-weight: 700;
      line-height: 1.3;
    }
    
    h1 {
      font-size: 42px;
      line-height: 52px;
      font-weight: 800;
      letter-spacing: -0.5px;
    }
    
    h2 {
      font-size: 32px;
      line-height: 42px;
      margin-bottom: 16px;
    }
    
    h3 {
      font-size: 20px;
      line-height: 28px;
      font-weight: 600;
    }
    
    h4 {
      font-size: 18px;
      line-height: 26px;
      font-weight: 600;
    }
    
    .section-title {
      text-align: center;
      margin-bottom: 48px;
    }
    
    .section-title h2 {
      margin-bottom: 12px;
    }
    
    .section-title p {
      color: var(--text-secondary);
      max-width: 680px;
      margin: 0 auto;
      font-size: 16px;
    }
    
    /* ---- Buttons ---- */
    .btn {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      padding: 14px 32px;
      border-radius: var(--radius-btn);
      font-weight: 600;
      font-size: 16px;
      transition: all var(--transition-smooth);
      text-align: center;
      white-space: nowrap;
    }
    
    .btn-primary {
      background: var(--primary);
      color: white;
      box-shadow: 0 4px 12px rgba(232,69,30,0.3);
    }
    
    .btn-primary:hover {
      background: var(--primary-deep);
      transform: translateY(-1px);
      box-shadow: 0 8px 20px rgba(232,69,30,0.4);
    }
    
    .btn-outline {
      background: transparent;
      border: 2px solid var(--primary);
      color: var(--primary);
    }
    
    .btn-outline:hover {
      background: var(--primary-soft);
    }
    
    .btn-ghost {
      background: transparent;
      border: 2px solid white;
      color: white;
    }
    
    .btn-ghost:hover {
      background: rgba(255,255,255,0.1);
    }
    
    .btn-small {
      padding: 10px 20px;
      font-size: 14px;
    }
    
    /* ---- Navigation ---- */
    .site-header {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      z-index: 1000;
      transition: background 0.3s ease, backdrop-filter 0.3s ease, box-shadow 0.3s ease;
      background: transparent;
      padding: 16px 0;
    }
    
    .site-header.scrolled {
      background: rgba(255,255,255,0.85);
      backdrop-filter: blur(16px);
      -webkit-backdrop-filter: blur(16px);
      box-shadow: 0 1px 8px rgba(0,0,0,0.06);
      border-bottom: 1px solid rgba(0,0,0,0.05);
    }
    
    .header-inner {
      display: flex;
      align-items: center;
      justify-content: space-between;
    }
    
    .logo {
      font-size: 24px;
      font-weight: 800;
      color: white;
      display: flex;
      align-items: center;
      gap: 8px;
      transition: color 0.3s;
    }
    
    .scrolled .logo {
      color: var(--text-primary);
    }
    
    .logo-icon {
      width: 32px;
      height: 32px;
      background: var(--primary);
      border-radius: 6px;
      display: flex;
      align-items: center;
      justify-content: center;
      color: white;
      font-weight: 800;
      font-size: 18px;
    }
    
    .nav-links {
      display: flex;
      align-items: center;
      gap: 32px;
    }
    
    .nav-links a {
      font-weight: 500;
      color: rgba(255,255,255,0.9);
      transition: color 0.2s;
      font-size: 15px;
    }
    
    .scrolled .nav-links a {
      color: var(--text-primary);
    }
    
    .nav-links a:hover {
      color: var(--primary);
    }
    
    .hamburger {
      display: none;
      flex-direction: column;
      gap: 5px;
      cursor: pointer;
      z-index: 1001;
    }
    
    .hamburger span {
      width: 24px;
      height: 2px;
      background: white;
      transition: 0.3s;
      display: block;
    }
    
    .scrolled .hamburger span {
      background: var(--text-primary);
    }
    
    /* Mobile menu */
    .mobile-menu {
      position: fixed;
      top: 0;
      right: -100%;
      width: 80%;
      max-width: 400px;
      height: 100vh;
      background: var(--surface);
      box-shadow: -8px 0 30px rgba(0,0,0,0.1);
      padding: 80px 32px 32px;
      display: flex;
      flex-direction: column;
      gap: 24px;
      transition: right 0.4s ease;
      z-index: 1000;
    }
    
    .mobile-menu.active {
      right: 0;
    }
    
    .mobile-menu a {
      font-size: 20px;
      font-weight: 600;
      color: var(--text-primary);
      padding: 8px 0;
      border-bottom: 1px solid var(--border-medium);
    }
    
    /* ---- Hero Section ---- */
    .hero {
      background: linear-gradient(135deg, var(--dark-bg) 0%, var(--dark-bg-alt) 100%);
      min-height: 100vh;
      display: flex;
      align-items: center;
      position: relative;
      overflow: hidden;
      color: white;
      padding: 120px 0 80px;
    }
    
    .hero::before {
      content: '';
      position: absolute;
      top: -20%;
      right: -10%;
      width: 60%;
      height: 120%;
      background: repeating-linear-gradient(45deg, transparent, transparent 40px, rgba(255,255,255,0.02) 40px, rgba(255,255,255,0.02) 42px);
      pointer-events: none;
      transform: skewX(-12deg);
    }
    
    .hero-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 60px;
      align-items: center;
      position: relative;
      z-index: 2;
    }
    
    .hero-content h1 {
      margin-bottom: 20px;
      color: white;
    }
    
    .hero-content p {
      font-size: 18px;
      color: rgba(255,255,255,0.8);
      margin-bottom: 32px;
      max-width: 500px;
    }
    
    .hero-buttons {
      display: flex;
      gap: 16px;
      flex-wrap: wrap;
    }
    
    .hero-image {
      background: url('/assets/images/backpic/back-1.webp') center/cover no-repeat;
      border-radius: 24px;
      height: 420px;
      box-shadow: 0 20px 40px rgba(0,0,0,0.4);
      border: 1px solid rgba(255,255,255,0.1);
    }
    
    /* ---- Features Section ---- */
    .features {
      padding: var(--spacing-section) 0;
      background: var(--surface);
    }
    
    .features-grid {
      display: grid;
      grid-template-columns: 1.2fr 0.8fr 1fr;
      gap: 24px;
    }
    
    .feature-card {
      background: var(--surface);
      border: 1px solid var(--border-light);
      border-radius: var(--radius-card);
      padding: 32px;
      transition: all var(--transition-smooth);
      box-shadow: var(--shadow-sm);
    }
    
    .feature-card:hover {
      transform: translateY(-4px);
      box-shadow: var(--shadow-hover);
    }
    
    .feature-icon {
      width: 48px;
      height: 48px;
      background: var(--primary-soft);
      border-radius: 10px;
      display: flex;
      align-items: center;
      justify-content: center;
      margin-bottom: 20px;
      color: var(--primary);
      font-size: 24px;
    }
    
    /* ---- Scenarios ---- */
    .scenarios {
      padding: var(--spacing-section) 0;
      background: var(--bg-light-gray);
    }
    
    .scroll-cards {
      display: flex;
      gap: 24px;
      overflow-x: auto;
      scroll-snap-type: x mandatory;
      padding-bottom: 16px;
      -webkit-overflow-scrolling: touch;
    }
    
    .scroll-cards::-webkit-scrollbar {
      height: 6px;
    }
    
    .scroll-cards::-webkit-scrollbar-thumb {
      background: var(--primary);
      border-radius: 10px;
    }
    
    .scene-card {
      flex: 0 0 340px;
      scroll-snap-align: start;
      background: white;
      border-radius: var(--radius-card);
      overflow: hidden;
      box-shadow: var(--shadow-sm);
      transition: transform 0.3s;
    }
    
    .scene-card:hover {
      transform: translateY(-6px);
    }
    
    .scene-img {
      height: 180px;
      background-size: cover;
      background-position: center;
    }
    
    .scene-info {
      padding: 20px;
    }
    
    /* ---- Cases / Data ---- */
    .data-section {
      padding: var(--spacing-section) 0;
      background: var(--dark-bg);
      color: white;
    }
    
    .stats-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 40px;
      text-align: center;
      margin-bottom: 60px;
    }
    
    .stat-number {
      font-family: var(--font-mono);
      font-size: 48px;
      font-weight: 800;
      color: var(--accent-gold);
      display: block;
    }
    
    .brand-strip {
      display: flex;
      justify-content: center;
      align-items: center;
      gap: 48px;
      flex-wrap: wrap;
      opacity: 0.7;
      filter: grayscale(100%) brightness(2);
    }
    
    /* ---- FAQ ---- */
    .faq {
      padding: var(--spacing-section) 0;
      background: var(--surface);
    }
    
    .faq-list {
      max-width: 800px;
      margin: 0 auto;
    }
    
    .faq-item {
      border: 1px solid var(--border-medium);
      border-radius: 8px;
      margin-bottom: 16px;
      overflow: hidden;
      transition: border-color 0.2s;
    }
    
    .faq-item.active {
      border-color: var(--primary);
    }
    
    .faq-question {
      width: 100%;
      padding: 20px 24px;
      display: flex;
      justify-content: space-between;
      align-items: center;
      background: white;
      font-weight: 600;
      font-size: 18px;
      text-align: left;
    }
    
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.35s ease, padding 0.35s ease;
      background: white;
      padding: 0 24px;
      color: var(--text-secondary);
    }
    
    .faq-item.active .faq-answer {
      max-height: 200px;
      padding: 0 24px 20px;
    }
    
    /* ---- CTA Banner ---- */
    .cta-banner {
      background: var(--primary);
      padding: 80px 0;
      text-align: center;
      color: white;
    }
    
    /* ---- Footer ---- */
    .site-footer {
      background: var(--dark-bg);
      color: var(--text-muted-on-dark);
      padding: 60px 0 30px;
    }
    
    .footer-grid {
      display: grid;
      grid-template-columns: 1.5fr 1fr 1fr 1fr;
      gap: 40px;
      margin-bottom: 40px;
    }
    
    .footer-bottom {
      border-top: 1px solid rgba(255,255,255,0.1);
      padding-top: 24px;
      text-align: center;
      font-size: 14px;
    }
    
    /* ---- Responsive ---- */
    @media (max-width: 1024px) {
      h1 { font-size: 36px; line-height: 46px; }
      .hero-grid { grid-template-columns: 1fr; gap: 40px; }
      .hero-image { height: 300px; }
      .features-grid { grid-template-columns: 1fr 1fr; }
    }
    
    @media (max-width: 768px) {
      .nav-links { display: none; }
      .hamburger { display: flex; }
      .container { padding-left: 20px; padding-right: 20px; }
      h1 { font-size: 28px; line-height: 38px; }
      h2 { font-size: 26px; }
      .hero { padding: 100px 0 60px; }
      .features-grid { grid-template-columns: 1fr; }
      .stats-grid { grid-template-columns: 1fr; gap: 32px; }
      .footer-grid { grid-template-columns: 1fr 1fr; }
      .btn { padding: 14px 24px; width: 100%; }
      .hero-buttons .btn { width: auto; }
    }
    
    @media (max-width: 520px) {
      .scroll-cards { gap: 16px; }
      .scene-card { flex: 0 0 280px; }
    }