/* roulang page: index */
:root {
      --primary: #4E6EF2;
      --primary-hover: #3A5AD9;
      --primary-soft: rgba(78,110,242,0.08);
      --green: #00B578;
      --orange: #FF9F0A;
      --red: #FA5151;
      --bg: #F5F6FA;
      --card: #FFFFFF;
      --text: #1F2329;
      --text-secondary: #86909C;
      --border: #E0E3E8;
      --shadow: 0 2px 8px rgba(0,0,0,0.04), 0 4px 16px rgba(0,0,0,0.04);
      --radius-card: 12px;
      --radius-btn: 8px;
      --radius-input: 8px;
      --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", "Helvetica Neue", sans-serif;
      --max-width: 1200px;
      --nav-height: 64px;
    }

    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    html {
      scroll-behavior: smooth;
    }

    body {
      font-family: var(--font-sans);
      background-color: var(--bg);
      color: var(--text);
      line-height: 1.6;
      -webkit-font-smoothing: antialiased;
      -moz-osx-font-smoothing: grayscale;
    }

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

    a {
      color: inherit;
      text-decoration: none;
      transition: color 0.2s ease;
    }

    .container {
      max-width: var(--max-width);
      margin-left: auto;
      margin-right: auto;
      padding-left: 24px;
      padding-right: 24px;
    }

    /* Header & Navigation */
    .site-header {
      position: sticky;
      top: 0;
      z-index: 50;
      background: rgba(255,255,255,0.92);
      backdrop-filter: blur(8px);
      -webkit-backdrop-filter: blur(8px);
      height: var(--nav-height);
      display: flex;
      align-items: center;
      border-bottom: 1px solid rgba(0,0,0,0.04);
    }

    .header-inner {
      display: flex;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      max-width: var(--max-width);
      margin: 0 auto;
      padding: 0 24px;
    }

    .logo {
      font-size: 22px;
      font-weight: 700;
      color: var(--primary);
      letter-spacing: 1px;
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .logo-icon {
      width: 28px;
      height: 28px;
      background: var(--primary);
      border-radius: 6px;
      display: flex;
      align-items: center;
      justify-content: center;
      color: white;
      font-size: 16px;
      font-weight: 700;
    }

    .nav-menu {
      display: flex;
      align-items: center;
      gap: 28px;
      list-style: none;
    }

    .nav-menu a {
      font-size: 15px;
      color: var(--text);
      font-weight: 500;
      padding: 6px 0;
      position: relative;
      transition: color 0.2s;
    }

    .nav-menu a:hover,
    .nav-menu a.active {
      color: var(--primary);
    }

    .nav-cta {
      margin-left: 16px;
      display: inline-block;
      padding: 10px 22px;
      border: 1px solid var(--primary);
      color: var(--primary);
      font-weight: 600;
      font-size: 15px;
      border-radius: var(--radius-btn);
      transition: all 0.2s ease;
      white-space: nowrap;
    }

    .nav-cta:hover {
      background: var(--primary-soft);
    }

    .hamburger {
      display: none;
      background: none;
      border: none;
      font-size: 24px;
      color: var(--text);
      cursor: pointer;
      width: 36px;
      height: 36px;
      align-items: center;
      justify-content: center;
    }

    .mobile-menu-overlay {
      display: none;
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: rgba(0,0,0,0.3);
      z-index: 40;
    }

    .mobile-drawer {
      position: fixed;
      top: 0;
      right: 0;
      width: 70%;
      max-width: 320px;
      height: 100%;
      background: white;
      z-index: 45;
      padding: 24px;
      transform: translateX(100%);
      transition: transform 0.3s ease;
      display: flex;
      flex-direction: column;
      gap: 20px;
    }

    .mobile-drawer.open {
      transform: translateX(0);
    }

    .mobile-drawer a {
      font-size: 18px;
      font-weight: 500;
      padding: 8px 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: 16px;
      transition: all 0.2s ease;
      cursor: pointer;
      border: none;
      text-align: center;
    }

    .btn-primary {
      background: var(--primary);
      color: white;
    }

    .btn-primary:hover {
      background: var(--primary-hover);
    }

    .btn-outline {
      background: transparent;
      border: 1px solid var(--primary);
      color: var(--primary);
    }

    .btn-outline:hover {
      background: var(--primary-soft);
    }

    /* Hero */
    .hero {
      padding: 60px 0 80px;
      background: var(--bg);
    }

    .hero-grid {
      display: flex;
      align-items: center;
      gap: 48px;
    }

    .hero-content {
      flex: 1 1 50%;
    }

    .hero-visual {
      flex: 1 1 50%;
      background: #E8EBF0;
      border-radius: 24px;
      overflow: hidden;
      min-height: 360px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    .hero-visual img {
      width: 100%;
      height: 100%;
      object-fit: cover;
    }

    h1 {
      font-size: 36px;
      font-weight: 700;
      line-height: 1.3;
      color: var(--text);
      margin-bottom: 16px;
    }

    .hero-sub {
      font-size: 20px;
      font-weight: 600;
      color: var(--primary);
      margin-bottom: 12px;
    }

    .hero-desc {
      font-size: 16px;
      color: var(--text-secondary);
      max-width: 460px;
      margin-bottom: 28px;
      line-height: 1.7;
    }

    .hero-buttons {
      display: flex;
      gap: 14px;
      flex-wrap: wrap;
    }

    /* Section spacing */
    section {
      padding: 80px 0;
    }

    .section-title {
      font-size: 28px;
      font-weight: 700;
      margin-bottom: 36px;
      color: var(--text);
    }

    /* Features */
    #features {
      background: var(--bg);
    }

    .features-grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 24px;
    }

    .feature-card {
      background: var(--card);
      border-radius: var(--radius-card);
      padding: 24px;
      box-shadow: var(--shadow);
      transition: transform 0.2s ease, box-shadow 0.2s ease;
    }

    .feature-card:hover {
      transform: translateY(-2px);
      box-shadow: 0 6px 20px rgba(0,0,0,0.06);
    }

    .feature-icon {
      font-size: 28px;
      color: var(--primary);
      margin-bottom: 16px;
      display: inline-block;
    }

    .feature-card h3 {
      font-size: 20px;
      margin-bottom: 8px;
    }

    .feature-card p {
      color: var(--text-secondary);
      font-size: 15px;
      line-height: 1.7;
    }

    /* Services */
    #services {
      background: white;
    }

    .services-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 24px;
    }

    .service-card {
      background: var(--card);
      border-radius: var(--radius-card);
      box-shadow: var(--shadow);
      overflow: hidden;
      transition: transform 0.2s;
      border-top: 4px solid var(--primary);
      transition: border-width 0.2s;
    }

    .service-card:hover {
      transform: translateY(-2px);
      border-top-width: 6px;
    }

    .service-img {
      background: #E8EBF0;
      aspect-ratio: 16/9;
      overflow: hidden;
    }

    .service-img img {
      width: 100%;
      height: 100%;
      object-fit: cover;
    }

    .service-body {
      padding: 20px 24px 24px;
    }

    .service-body h3 {
      font-size: 20px;
      margin-bottom: 12px;
    }

    .service-body ul {
      list-style: none;
      color: var(--text-secondary);
      font-size: 15px;
      line-height: 1.8;
      margin-bottom: 16px;
    }

    .service-link {
      color: var(--primary);
      font-weight: 600;
      font-size: 15px;
    }

    /* Data comparison */
    #data {
      background: #EEF0F7;
    }

    .data-wrapper {
      display: flex;
      background: white;
      border-radius: var(--radius-card);
      box-shadow: var(--shadow);
      overflow: hidden;
    }

    .data-col {
      flex: 1;
      padding: 32px 40px;
      display: flex;
      flex-direction: column;
      gap: 24px;
    }

    .data-col.left {
      border-right: 1px solid #F0F2F5;
    }

    .data-label {
      font-weight: 700;
      font-size: 18px;
      margin-bottom: 8px;
    }

    .data-item {
      display: flex;
      align-items: baseline;
      gap: 6px;
      font-size: 42px;
      font-weight: 700;
    }

    .data-unit {
      font-size: 20px;
      font-weight: 500;
    }

    .data-desc {
      font-size: 14px;
      color: var(--text-secondary);
    }

    .data-col.left .data-item {
      color: var(--text-secondary);
    }

    .data-col.right .data-item {
      color: var(--primary);
    }

    .green-highlight {
      color: var(--green);
    }

    /* FAQ */
    #faq {
      background: var(--bg);
    }

    .faq-list {
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    .faq-item {
      background: white;
      border-radius: var(--radius-card);
      box-shadow: 0 1px 4px rgba(0,0,0,0.02);
      overflow: hidden;
    }

    .faq-question {
      padding: 16px 20px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      font-weight: 600;
      font-size: 16px;
      cursor: pointer;
      background: white;
      user-select: none;
    }

    .faq-icon {
      font-size: 20px;
      transition: transform 0.3s ease;
    }

    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.3s ease, padding 0.3s ease;
      background: #FAFBFC;
      font-size: 15px;
      color: var(--text-secondary);
      line-height: 1.7;
    }

    .faq-item.open .faq-answer {
      max-height: 200px;
      padding: 16px 20px;
    }

    .faq-item.open .faq-icon {
      transform: rotate(45deg);
    }

    /* CTA */
    #contact {
      background: linear-gradient(180deg, #F5F6FA 0%, #EEF0FB 100%);
    }

    .cta-inner {
      text-align: center;
      max-width: 680px;
      margin: 0 auto;
    }

    .cta-form {
      display: flex;
      gap: 12px;
      margin-top: 28px;
      flex-wrap: wrap;
      justify-content: center;
    }

    .cta-form input {
      padding: 12px 16px;
      border: 1px solid var(--border);
      border-radius: var(--radius-input);
      font-size: 16px;
      background: white;
      flex: 1 1 200px;
      transition: border 0.2s, box-shadow 0.2s;
    }

    .cta-form input:focus {
      outline: none;
      border-color: var(--primary);
      box-shadow: 0 0 0 3px rgba(78,110,242,0.15);
    }

    /* Footer */
    .site-footer {
      background: #1F2329;
      color: #C9CDD4;
      padding: 36px 0;
      text-align: center;
      font-size: 14px;
    }

    .footer-logo {
      font-weight: 700;
      font-size: 20px;
      color: white;
      margin-bottom: 12px;
    }

    .footer-links {
      display: flex;
      gap: 24px;
      justify-content: center;
      margin: 12px 0;
    }

    .footer-links a {
      color: #C9CDD4;
    }

    .footer-links a:hover {
      color: var(--primary);
    }

    /* Responsive */
    @media (max-width: 1024px) {
      .hero-visual {
        min-height: 280px;
      }
    }

    @media (max-width: 768px) {
      .nav-menu {
        display: none;
      }
      .nav-cta.desktop {
        display: none;
      }
      .hamburger {
        display: flex;
      }
      .hero-grid {
        flex-direction: column;
      }
      .hero-visual {
        width: 100%;
        min-height: 240px;
      }
      h1 {
        font-size: 28px;
      }
      .section-title {
        font-size: 24px;
      }
      .features-grid,
      .services-grid {
        grid-template-columns: 1fr;
      }
      .data-wrapper {
        flex-direction: column;
      }
      .data-col.left {
        border-right: none;
        border-bottom: 1px solid #F0F2F5;
      }
      .cta-form {
        flex-direction: column;
      }
      .cta-form input {
        width: 100%;
      }
      .btn {
        width: 100%;
      }
      section {
        padding: 60px 0;
      }
    }

    @media (max-width: 520px) {
      .container {
        padding-left: 16px;
        padding-right: 16px;
      }
    }