/* roulang page: index */
/* ===== CSS RESET & BASE ===== */
    *, *::before, *::after {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    
    :root {
      /* Brand Colors */
      --primary: #1A3B5C;
      --secondary: #00B4D8;
      --accent: #FF8C42;
      --bg-light: #F8FAFC;
      --bg-subtle: #EEF2F6;
      --text-dark: #1E293B;
      --text-muted: #64748B;
      --white: #FFFFFF;
      --border-light: #E2E8F0;
      
      /* Shadows & Radii */
      --shadow-sm: 0 2px 8px rgba(0,0,0,0.04), 0 1px 2px rgba(0,0,0,0.06);
      --shadow-hover: 0 8px 24px rgba(0,0,0,0.08), 0 2px 6px rgba(0,0,0,0.06);
      --radius-card: 12px;
      --radius-btn: 8px;
      --radius-img: 16px;
      
      /* Typography */
      --font-sans: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
      
      /* Layout */
      --max-width: 1200px;
      --section-padding: 100px 24px;
      --nav-height: 64px;
      --transition: 0.25s ease-in-out;
    }
    
    html {
      scroll-behavior: smooth;
      -webkit-text-size-adjust: 100%;
    }
    
    body {
      font-family: var(--font-sans);
      font-weight: 400;
      font-size: 16px;
      line-height: 1.7;
      color: var(--text-dark);
      background-color: var(--bg-light);
      padding-top: var(--nav-height);
      overflow-x: hidden;
    }
    
    img {
      max-width: 100%;
      height: auto;
      display: block;
    }
    
    a {
      text-decoration: none;
      color: inherit;
      transition: color var(--transition);
    }
    
    button, .btn {
      font-family: inherit;
      cursor: pointer;
      border: none;
      background: none;
    }
    
    .container {
      max-width: var(--max-width);
      margin: 0 auto;
      padding: 0 24px;
      width: 100%;
    }
    
    /* ===== SYSTEM UTILITIES ===== */
    .sr-only {
      position: absolute;
      width: 1px;
      height: 1px;
      padding: 0;
      margin: -1px;
      overflow: hidden;
      clip: rect(0, 0, 0, 0);
      white-space: nowrap;
      border: 0;
    }
    
    /* ===== TYPOGRAPHY ===== */
    h1, h2, h3 {
      font-weight: 600;
      line-height: 1.3;
      color: var(--primary);
    }
    
    h1 {
      font-size: clamp(2.2rem, 6vw, 3.5rem);
      font-weight: 700;
    }
    
    h2 {
      font-size: clamp(1.8rem, 4vw, 2.25rem);
      margin-bottom: 1rem;
      color: var(--primary);
    }
    
    h3 {
      font-size: 1.25rem;
      font-weight: 600;
    }
    
    /* ===== NAVIGATION ===== */
    .nav {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: var(--nav-height);
      background: var(--white);
      border-bottom: 1px solid var(--border-light);
      z-index: 1000;
      display: flex;
      align-items: center;
      transition: box-shadow var(--transition);
    }
    
    .nav.scrolled {
      box-shadow: var(--shadow-sm);
    }
    
    .nav-container {
      display: flex;
      justify-content: space-between;
      align-items: center;
      width: 100%;
    }
    
    .logo {
      display: flex;
      align-items: center;
      gap: 10px;
      font-weight: 700;
      font-size: 1.4rem;
      color: var(--primary);
      letter-spacing: -0.3px;
      text-decoration: none;
    }
    
    .logo-icon {
      width: 32px;
      height: 32px;
      background: var(--secondary);
      border-radius: 8px;
      display: flex;
      align-items: center;
      justify-content: center;
      color: white;
      font-size: 18px;
      font-weight: 700;
      box-shadow: 0 2px 6px rgba(0,180,216,0.3);
    }
    
    .nav-menu {
      display: flex;
      list-style: none;
      gap: 2.5rem;
      align-items: center;
    }
    
    .nav-link {
      font-weight: 500;
      font-size: 1rem;
      color: var(--text-dark);
      position: relative;
      padding: 0.25rem 0;
      transition: color var(--transition);
    }
    
    .nav-link::after {
      content: '';
      position: absolute;
      bottom: -4px;
      left: 0;
      width: 0;
      height: 2px;
      background: var(--secondary);
      transition: width var(--transition);
    }
    
    .nav-link:hover,
    .nav-link.active {
      color: var(--secondary);
    }
    
    .nav-link:hover::after,
    .nav-link.active::after {
      width: 100%;
    }
    
    .hamburger {
      display: none;
      flex-direction: column;
      gap: 5px;
      cursor: pointer;
      padding: 4px;
      background: transparent;
      border: none;
    }
    
    .hamburger span {
      display: block;
      width: 24px;
      height: 2px;
      background: var(--primary);
      border-radius: 2px;
      transition: transform 0.3s, opacity 0.2s;
    }
    
    /* Mobile menu overlay */
    .mobile-overlay {
      position: fixed;
      top: var(--nav-height);
      left: 0;
      width: 100%;
      height: 100vh;
      background: var(--white);
      transform: translateX(100%);
      transition: transform 0.3s ease;
      z-index: 999;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 2rem;
      list-style: none;
    }
    .mobile-overlay.open {
      transform: translateX(0);
    }
    
    /* ===== BUTTONS ===== */
    .btn {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      padding: 12px 28px;
      border-radius: var(--radius-btn);
      font-weight: 600;
      font-size: 1rem;
      letter-spacing: 0.5px;
      transition: all 0.25s ease;
      text-align: center;
      white-space: nowrap;
    }
    
    .btn-primary {
      background: var(--secondary);
      color: var(--white);
      box-shadow: 0 4px 10px rgba(0,180,216,0.25);
    }
    .btn-primary:hover {
      background: var(--accent);
      box-shadow: 0 8px 16px rgba(255,140,66,0.3);
      transform: scale(1.03);
    }
    .btn-outline {
      background: transparent;
      border: 2px solid var(--primary);
      color: var(--primary);
    }
    .btn-outline:hover {
      background: var(--primary);
      color: white;
      transform: scale(1.03);
      border-color: var(--primary);
    }
    
    /* ===== HERO ===== */
    .hero {
      background: var(--bg-light);
      padding: 80px 0;
    }
    
    .hero-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 50px;
      align-items: center;
    }
    
    .hero-content {
      max-width: 550px;
    }
    
    .hero-content h1 {
      margin-bottom: 1.5rem;
    }
    
    .hero-subtitle {
      font-size: 1.15rem;
      color: var(--text-muted);
      margin-bottom: 2rem;
      line-height: 1.7;
    }
    
    .hero-buttons {
      display: flex;
      gap: 16px;
      flex-wrap: wrap;
    }
    
    .hero-image img {
      width: 100%;
      border-radius: var(--radius-img);
      box-shadow: var(--shadow-hover);
    }
    
    /* ===== SECTION SPACING ===== */
    section {
      padding: var(--section-padding);
    }
    .bg-alternate {
      background-color: var(--bg-subtle);
    }
    
    .section-header {
      text-align: center;
      max-width: 700px;
      margin: 0 auto 48px;
    }
    .section-header p {
      color: var(--text-muted);
    }
    
    /* ===== HIGHLIGHTS GRID ===== */
    .highlights-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 28px;
    }
    
    .highlight-card {
      background: var(--white);
      padding: 32px;
      border-radius: var(--radius-card);
      box-shadow: var(--shadow-sm);
      transition: all 0.3s ease;
      text-align: left;
    }
    .highlight-card:hover {
      transform: translateY(-6px);
      box-shadow: var(--shadow-hover);
    }
    .icon-circle {
      width: 56px;
      height: 56px;
      border-radius: 50%;
      background: #E0F2FE;
      display: flex;
      align-items: center;
      justify-content: center;
      margin-bottom: 1.5rem;
      font-size: 1.6rem;
      color: var(--secondary);
    }
    .highlight-card h3 {
      margin-bottom: 0.6rem;
    }
    
    /* ===== CASE WATERFALL ===== */
    .cases-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 28px;
    }
    .case-card {
      background: var(--white);
      border-radius: var(--radius-card);
      overflow: hidden;
      box-shadow: var(--shadow-sm);
      transition: all 0.3s ease;
    }
    .case-card:hover {
      transform: translateY(-4px);
      box-shadow: var(--shadow-hover);
    }
    .case-card img {
      width: 100%;
      aspect-ratio: 16 / 9;
      object-fit: cover;
    }
    .case-info {
      padding: 20px;
    }
    .case-tag {
      background: var(--accent);
      color: white;
      font-size: 0.8rem;
      padding: 2px 12px;
      border-radius: 50px;
      display: inline-block;
      margin-bottom: 0.5rem;
      font-weight: 600;
    }
    .case-title {
      font-weight: 700;
      margin-bottom: 0.25rem;
    }
    
    /* ===== PLAN COMPARISON ===== */
    .plan-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 28px;
      align-items: start;
    }
    .plan-card {
      background: var(--white);
      border-radius: var(--radius-card);
      padding: 32px;
      box-shadow: var(--shadow-sm);
      border: 1px solid var(--border-light);
      transition: all 0.3s;
      position: relative;
    }
    .plan-card.featured {
      border-color: var(--secondary);
      background: #F0F9FF;
      box-shadow: 0 12px 24px rgba(0,180,216,0.1);
    }
    .plan-header {
      font-size: 1.3rem;
      font-weight: 700;
      color: var(--primary);
      margin-bottom: 1.5rem;
    }
    .plan-item {
      display: flex;
      align-items: center;
      gap: 8px;
      margin-bottom: 12px;
      font-size: 0.95rem;
    }
    .check-icon {
      color: var(--secondary);
      font-weight: bold;
    }
    .unavailable {
      color: #cbd5e1;
    }
    
    /* ===== FAQ ===== */
    .faq-list {
      max-width: 800px;
      margin: 0 auto;
    }
    .faq-item {
      border-bottom: 1px solid var(--border-light);
    }
    .faq-question {
      width: 100%;
      text-align: left;
      padding: 20px 8px;
      font-weight: 600;
      font-size: 1.1rem;
      display: flex;
      justify-content: space-between;
      align-items: center;
      background: transparent;
      transition: color 0.2s;
    }
    .faq-question:hover {
      color: var(--secondary);
    }
    .faq-icon {
      font-size: 1.4rem;
      transition: transform 0.3s;
    }
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.4s ease;
      background: #f1f5f9;
      border-radius: 8px;
      margin-bottom: 4px;
    }
    .faq-answer p {
      padding: 0 16px 16px;
      margin: 0;
    }
    .faq-item.active .faq-answer {
      max-height: 200px;
    }
    .faq-item.active .faq-icon {
      transform: rotate(45deg);
    }
    
    /* ===== CTA STRIP ===== */
    .cta-strip {
      background: linear-gradient(105deg, #1A3B5C 0%, #0F5B7A 100%);
      color: white;
      text-align: center;
      padding: 80px 24px;
    }
    .cta-strip h2 {
      color: white;
    }
    .cta-strip .btn-primary {
      background: var(--accent);
    }
    
    /* ===== FOOTER ===== */
    .footer {
      background: #0F1A2E;
      color: #cbd5e1;
      padding: 60px 24px 30px;
    }
    .footer-grid {
      display: grid;
      grid-template-columns: 2fr 1fr 1fr 1fr;
      gap: 40px;
    }
    .footer-logo {
      font-weight: 700;
      font-size: 1.5rem;
      color: white;
    }
    .copyright {
      text-align: center;
      margin-top: 40px;
      border-top: 1px solid #334155;
      padding-top: 24px;
      color: #94a3b8;
    }
    
    /* ===== RESPONSIVE ===== */
    @media (max-width: 1024px) {
      .hero-grid { grid-template-columns: 1fr; }
      .hero-image { order: -1; }
      .highlights-grid, .cases-grid, .plan-grid { grid-template-columns: repeat(2, 1fr); }
    }
    @media (max-width: 768px) {
      .nav-menu { display: none; }
      .hamburger { display: flex; }
      .highlights-grid, .cases-grid, .plan-grid { grid-template-columns: 1fr; }
      .footer-grid { grid-template-columns: 1fr 1fr; }
    }