/* roulang page: index */
:root {
      /* 色彩方案 - 自然材质气质 */
      --color-primary-bg: #F5F4EF;
      --color-charcoal-black: #2B2B2B;
      --color-lime-white: #F5F4EF;
      --color-field-green: #4A7C59;
      --color-mist-gray: #E8E5DF;
      --color-dark-charcoal: #1A1A1A;
      --color-text-main: #2B2B2B;
      --color-text-secondary: #5C5C5C;
      --color-text-muted: #8A8A8A;
      
      --font-primary: "PingFang SC", "Microsoft YaHei", "Hiragino Sans GB", "Inter", system-ui, -apple-system, sans-serif;
      --font-number: "Inter", "PingFang SC", sans-serif;
      
      --shadow-light: 0 2px 8px rgba(0,0,0,0.04);
      --shadow-hover: 0 8px 24px rgba(0,0,0,0.08);
      --border-radius-sm: 8px;
      --border-radius-md: 12px;
      --transition-base: 0.25s cubic-bezier(0.25, 0.46, 0.45, 0.94);
      --transition-smooth: 0.3s ease;
    }

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

    body {
      font-family: var(--font-primary);
      background-color: var(--color-primary-bg);
      color: var(--color-text-main);
      line-height: 1.5;
      -webkit-font-smoothing: antialiased;
      scroll-behavior: smooth;
    }

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

    a {
      text-decoration: none;
      color: inherit;
    }

    button, input {
      font-family: inherit;
    }

    .container {
      max-width: 1280px;
      margin: 0 auto;
      padding: 0 40px;
    }

    @media (max-width: 768px) {
      .container {
        padding: 0 24px;
      }
    }

    /* 板块通用间距 */
    section:not(#hero):not(#contact) {
      padding: 140px 0;
    }
    @media (max-width: 768px) {
      section:not(#hero):not(#contact) {
        padding: 80px 0;
      }
    }

    /* ===== 导航 (固定顶部) ===== */
    #header {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 72px;
      background-color: rgba(245, 244, 239, 0.92);
      backdrop-filter: blur(8px);
      border-bottom: 1px solid transparent;
      z-index: 1000;
      transition: background var(--transition-smooth), border var(--transition-smooth);
    }
    #header.scrolled {
      background-color: var(--color-lime-white);
      border-bottom: 1px solid var(--color-mist-gray);
      box-shadow: var(--shadow-light);
    }
    .nav-container {
      display: flex;
      align-items: center;
      justify-content: space-between;
      height: 100%;
    }
    .logo {
      display: flex;
      align-items: baseline;
      font-weight: 700;
      font-size: 1.5rem;
      color: var(--color-charcoal-black);
      letter-spacing: -0.5px;
    }
    .logo small {
      font-size: 0.8rem;
      font-weight: 500;
      margin-left: 4px;
      color: var(--color-text-muted);
    }
    .nav-links {
      display: flex;
      gap: 32px;
      align-items: center;
      list-style: none;
    }
    .nav-links a {
      font-size: 15px;
      font-weight: 500;
      color: var(--color-charcoal-black);
      padding: 4px 0;
      position: relative;
      transition: color 0.2s;
    }
    .nav-links a:hover,
    .nav-links a.active {
      color: var(--color-field-green);
    }
    .nav-links a::after {
      content: '';
      position: absolute;
      bottom: -6px;
      left: 0;
      width: 100%;
      height: 2px;
      background: var(--color-field-green);
      transform: scaleX(0);
      transition: transform 0.2s;
    }
    .nav-links a.active::after {
      transform: scaleX(1);
    }

    /* 汉堡菜单 */
    .hamburger {
      display: none;
      flex-direction: column;
      gap: 6px;
      background: none;
      border: none;
      cursor: pointer;
      padding: 4px;
    }
    .hamburger span {
      display: block;
      width: 26px;
      height: 2px;
      background: var(--color-charcoal-black);
      transition: var(--transition-base);
    }
    .mobile-menu {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100vh;
      background: var(--color-lime-white);
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 36px;
      z-index: 999;
      transform: translateY(-100%);
      transition: transform 0.35s ease-out;
    }
    .mobile-menu.active {
      transform: translateY(0);
    }
    .mobile-menu a {
      font-size: 22px;
      font-weight: 600;
      color: var(--color-charcoal-black);
    }
    .close-menu {
      position: absolute;
      top: 28px;
      right: 36px;
      background: none;
      border: none;
      font-size: 2rem;
      cursor: pointer;
    }

    @media (max-width: 768px) {
      .nav-links { display: none; }
      .hamburger { display: flex; }
    }

    /* ===== 首屏 Hero ===== */
    #hero {
      height: 100vh;
      min-height: 720px;
      display: flex;
      align-items: center;
      background: linear-gradient(120deg, #F5F4EF 0%, #ede9df 100%);
    }
    .hero-grid {
      display: grid;
      grid-template-columns: 7fr 5fr;
      gap: 30px;
      align-items: center;
      width: 100%;
    }
    .hero-content h1 {
      font-size: 52px;
      line-height: 1.15;
      font-weight: 700;
      color: var(--color-charcoal-black);
      margin-bottom: 24px;
      letter-spacing: -0.8px;
    }
    .hero-content p {
      font-size: 18px;
      color: var(--color-text-secondary);
      margin-bottom: 40px;
      max-width: 560px;
    }
    .cta-group {
      display: flex;
      gap: 20px;
      flex-wrap: wrap;
    }
    .btn-primary {
      background: var(--color-field-green);
      color: white;
      font-weight: 600;
      padding: 14px 36px;
      border-radius: var(--border-radius-sm);
      border: none;
      transition: background 0.2s ease;
      display: inline-block;
      cursor: pointer;
      font-size: 16px;
    }
    .btn-primary:hover { background: #3D6B4A; }
    .btn-secondary {
      background: transparent;
      border: 1.5px solid var(--color-charcoal-black);
      color: var(--color-charcoal-black);
      font-weight: 600;
      padding: 14px 36px;
      border-radius: var(--border-radius-sm);
      transition: all 0.2s;
      display: inline-block;
      cursor: pointer;
      font-size: 16px;
    }
    .btn-secondary:hover {
      background: var(--color-charcoal-black);
      color: white;
    }
    .hero-visual {
      display: flex;
      justify-content: center;
      align-items: center;
    }
    .abstract-stadium {
      width: 90%;
      height: auto;
    }

    @media (max-width: 1024px) {
      #hero { min-height: auto; padding: 120px 0 80px; }
      .hero-grid { grid-template-columns: 1fr; }
      .hero-content h1 { font-size: 40px; }
      .hero-visual { order: -1; margin-bottom: 30px; max-width: 320px; justify-self: start; }
    }
    @media (max-width: 768px) {
      .hero-content h1 { font-size: 35px; }
    }

    /* ===== 服务卡片 非对称 ===== */
    .services-grid {
      display: grid;
      grid-template-columns: 2fr 1fr;
      gap: 28px;
    }
    .service-card {
      background: var(--color-mist-gray);
      border-radius: var(--border-radius-md);
      padding: 36px 36px 30px;
      display: flex;
      flex-direction: column;
      border-left: 6px solid var(--color-field-green);
      transition: all var(--transition-base);
    }
    .service-card:hover {
      transform: translateY(-5px);
      box-shadow: var(--shadow-hover);
    }
    .card-icon {
      font-size: 42px;
      color: var(--color-field-green);
      margin-bottom: 18px;
    }
    .service-card h3 {
      font-size: 22px;
      font-weight: 600;
      margin-bottom: 14px;
    }
    .service-card p {
      color: var(--color-text-secondary);
      margin-bottom: 24px;
      flex: 1;
    }
    .text-link {
      color: var(--color-field-green);
      font-weight: 600;
      align-self: flex-start;
      transition: color 0.2s;
    }
    .text-link:hover { text-decoration: underline; }

    @media (max-width: 768px) {
      .services-grid { grid-template-columns: 1fr; }
      .service-card { border-left-width: 4px; }
    }

    /* ===== 优势数据 ===== */
    #advantages {
      background: var(--color-dark-charcoal);
      color: white;
    }
    .stats-grid {
      display: flex;
      justify-content: space-around;
      text-align: center;
      flex-wrap: wrap;
    }
    .stat-item {
      padding: 0 40px;
      border-right: 1px solid rgba(255,255,255,0.2);
    }
    .stat-item:last-child { border-right: none; }
    .stat-number {
      font-size: 64px;
      font-weight: 700;
      font-family: var(--font-number);
      color: var(--color-field-green);
      line-height: 1.1;
    }
    .stat-label {
      font-size: 16px;
      font-weight: 500;
      opacity: 0.9;
      margin-top: 8px;
    }
    @media (max-width: 768px) {
      .stats-grid { gap: 40px; }
      .stat-item { border: none; padding: 0 24px; }
      .stat-number { font-size: 48px; }
    }

    /* ===== 案例区 ===== */
    .cases-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 28px;
    }
    .case-card {
      position: relative;
      border-radius: var(--border-radius-md);
      overflow: hidden;
      background: #ccc;
      aspect-ratio: 4 / 3;
    }
    .case-card img {
      width: 100%;
      height: 100%;
      object-fit: cover;
      filter: grayscale(100%);
      transition: filter 0.4s, transform 0.4s;
    }
    .case-card:hover img {
      filter: grayscale(0%);
      transform: scale(1.03);
    }
    .case-overlay {
      position: absolute;
      top: 0; left: 0; width: 100%; height: 100%;
      background: rgba(74, 124, 89, 0.65);
      display: flex;
      align-items: center;
      justify-content: center;
      opacity: 0;
      transition: opacity 0.3s;
    }
    .case-card:hover .case-overlay { opacity: 1; }
    .case-title {
      color: white;
      font-weight: 700;
      font-size: 22px;
    }
    @media (max-width: 1024px) { .cases-grid { grid-template-columns: 1fr 1fr; } }
    @media (max-width: 540px) { .cases-grid { grid-template-columns: 1fr; } }

    /* FAQ */
    .faq-wrapper {
      display: grid;
      grid-template-columns: 1fr 2fr;
      gap: 60px;
    }
    .faq-list details {
      border-bottom: 1px solid var(--color-mist-gray);
      padding: 22px 0;
    }
    .faq-list summary {
      font-weight: 600;
      font-size: 18px;
      cursor: pointer;
      display: flex;
      justify-content: space-between;
      align-items: center;
    }
    .faq-list summary i {
      transition: transform 0.2s;
    }
    details[open] summary i {
      transform: rotate(45deg);
    }
    .answer {
      margin-top: 14px;
      color: var(--color-text-secondary);
    }
    @media (max-width: 768px) {
      .faq-wrapper { grid-template-columns: 1fr; gap: 30px; }
    }

    /* 联系/页脚 */
    #contact { background: var(--color-dark-charcoal); color: white; padding: 90px 0 40px; }
    .cta-center { text-align: center; margin-bottom: 70px; }
    .footer-grid {
      display: grid;
      grid-template-columns: 1.5fr 1fr 1fr 1fr;
      gap: 30px;
      margin-top: 50px;
    }
    .footer-col h4 { margin-bottom: 18px; }
    .footer-col a, .footer-col p { color: #ddd; font-size: 15px; line-height: 2; }
    .social-icons a { margin-right: 14px; font-size: 20px; color: #ccc; }
    .copyright { text-align: center; margin-top: 50px; color: var(--color-text-muted); font-size: 14px; }
    @media (max-width: 768px) { .footer-grid { grid-template-columns: 1fr; } }
    
    button { font-family: inherit; }