/* roulang page: index */
/* ----- 设计变量 ----- */
    :root {
      --deep-titanium: #1C1E21;
      --forge-orange: #F15A24;
      --cold-silver: #E0E4E8;
      --anodized-black: #0B0C0E;
      --bg-light: #F8F9FA;
      --bg-dark: #15171A;
      --text-primary: #1C1E21;
      --text-secondary: #4A4D52;
      --text-on-dark: #E0E4E8;
      --border-light: #E9EBED;
      --border-active: #F15A24;
      --shadow-sm: 0 4px 10px rgba(241, 90, 36, 0.08);
      --shadow-card: 0 8px 20px rgba(0,0,0,0.04);
      --shadow-elevated: 0 16px 32px rgba(241, 90, 36, 0.1);
      --radius-precision: 2px;
      --space-unit: 8px;
      --nav-width: 80px;
      --font-sans: 'Inter', 'PingFang SC', 'Microsoft YaHei', system-ui, -apple-system, sans-serif;
      --transition-smooth: 0.25s cubic-bezier(0.25, 0.46, 0.45, 0.94);
    }

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

    body {
      font-family: var(--font-sans);
      background-color: var(--bg-light);
      color: var(--text-primary);
      line-height: 1.7;
      font-weight: 400;
      font-size: 16px;
      display: flex;
      min-height: 100vh;
      overflow-x: hidden;
    }

    /* 左侧固定导航 (桌面) */
    .side-nav {
      position: fixed;
      left: 0;
      top: 0;
      width: var(--nav-width);
      height: 100vh;
      background-color: var(--anodized-black);
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      padding: 40px 0 24px;
      z-index: 1000;
      border-right: 1px solid rgba(224, 228, 232, 0.1);
    }

    .logo-area {
      writing-mode: vertical-rl;
      text-orientation: mixed;
      font-weight: 700;
      font-size: 18px;
      letter-spacing: 2px;
      color: var(--forge-orange);
      display: flex;
      align-items: center;
      gap: 8px;
    }

    .logo-icon {
      width: 24px;
      height: 24px;
      border: 2px solid var(--forge-orange);
      display: flex;
      align-items: center;
      justify-content: center;
      font-weight: 700;
      font-size: 14px;
      color: var(--forge-orange);
      margin-bottom: 8px;
      transform: rotate(90deg);
    }

    .nav-menu {
      display: flex;
      flex-direction: column;
      gap: 32px;
      writing-mode: vertical-rl;
      text-orientation: mixed;
    }

    .nav-link {
      color: var(--cold-silver);
      text-decoration: none;
      font-size: 14px;
      font-weight: 500;
      letter-spacing: 1px;
      transition: color var(--transition-smooth);
      position: relative;
    }

    .nav-link:hover,
    .nav-link.active {
      color: var(--forge-orange);
    }

    .nav-divider {
      width: 20px;
      height: 1px;
      background: rgba(224, 228, 232, 0.2);
      margin: 8px 0;
    }

    .main-content {
      margin-left: var(--nav-width);
      width: calc(100% - var(--nav-width));
      background: var(--bg-light);
    }

    /* 移动端底部导航 */
    .mobile-bottom-nav {
      display: none;
      position: fixed;
      bottom: 0;
      left: 0;
      width: 100%;
      background: rgba(11, 12, 14, 0.85);
      backdrop-filter: blur(20px);
      -webkit-backdrop-filter: blur(20px);
      border-top: 1px solid rgba(224, 228, 232, 0.15);
      flex-direction: row;
      justify-content: space-around;
      align-items: center;
      padding: 12px 16px;
      z-index: 1000;
    }

    .mobile-nav-link {
      color: var(--cold-silver);
      font-size: 12px;
      text-decoration: none;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 4px;
      font-weight: 500;
    }

    .mobile-nav-link.active {
      color: var(--forge-orange);
    }

    /* 容器与板块 */
    .container {
      max-width: 1280px;
      margin: 0 auto;
      padding: 0 40px;
    }

    section {
      padding: 120px 0;
      position: relative;
    }

    /* 按钮组件 */
    .btn-primary {
      background: var(--forge-orange);
      color: white;
      border: none;
      padding: 16px 32px;
      font-weight: 600;
      font-size: 16px;
      letter-spacing: 0.5px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 12px;
      transition: all var(--transition-smooth);
      border-radius: var(--radius-precision);
      text-decoration: none;
    }

    .btn-primary:hover {
      background: #d94a1a;
      gap: 18px;
      box-shadow: var(--shadow-elevated);
    }

    .arrow-icon {
      transition: transform var(--transition-smooth);
    }

    .btn-primary:hover .arrow-icon {
      transform: translateX(6px);
    }

    /* 卡片组件 */
    .card {
      background: white;
      border: 1px solid var(--border-light);
      border-radius: var(--radius-precision);
      padding: 40px 32px;
      transition: all 0.3s ease;
      position: relative;
      box-shadow: var(--shadow-card);
    }

    .card:hover {
      border-color: var(--border-active);
      transform: translateY(-4px);
      box-shadow: var(--shadow-elevated);
    }

    .metric-card {
      background: white;
      border: 1px solid var(--border-light);
      border-radius: var(--radius-precision);
      padding: 24px;
      text-align: left;
    }

    /* 排版 */
    h1 {
      font-size: 56px;
      line-height: 1.15;
      font-weight: 700;
      letter-spacing: -0.02em;
      color: var(--deep-titanium);
    }

    h2 {
      font-size: 40px;
      line-height: 1.2;
      font-weight: 600;
      letter-spacing: -0.01em;
      color: var(--deep-titanium);
      margin-bottom: 24px;
    }

    h3 {
      font-size: 24px;
      font-weight: 600;
      line-height: 1.3;
    }

    .text-secondary {
      color: var(--text-secondary);
    }

    .bg-dark-section {
      background-color: var(--bg-dark);
      color: var(--text-on-dark);
    }

    /* 数据看板 */
    .kpi-grid {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 24px;
      margin-top: 60px;
    }

    .kpi-number {
      font-size: 42px;
      font-weight: 700;
      font-family: 'Inter', sans-serif;
      color: var(--forge-orange);
      line-height: 1.1;
    }

    /* 服务矩阵非对称 */
    .service-matrix {
      display: grid;
      grid-template-columns: 5fr 7fr;
      gap: 40px;
    }

    .service-large-card {
      grid-row: span 2;
    }

    .service-stack {
      display: flex;
      flex-direction: column;
      gap: 24px;
    }

    .card-grid-line {
      background-image: linear-gradient(rgba(0,0,0,0.03) 1px, transparent 1px);
      background-size: 100% 8px;
    }

    /* 效能对比 */
    .comparison-split {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 60px;
      align-items: center;
    }

    .bar-chart-visual {
      background: rgba(255,255,255,0.05);
      padding: 24px;
      border-radius: var(--radius-precision);
    }

    .bar-item {
      display: flex;
      align-items: center;
      gap: 16px;
      margin-bottom: 24px;
    }

    .bar-fill {
      height: 12px;
      background: var(--forge-orange);
      width: 0%;
      transition: width 1s ease;
    }

    /* FAQ 双列 */
    .faq-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 24px;
    }

    .faq-item {
      border-left: 2px solid var(--forge-orange);
      padding-left: 24px;
      cursor: pointer;
      transition: background 0.2s;
    }

    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.4s ease, padding 0.3s;
      color: var(--text-secondary);
      font-size: 15px;
    }

    .faq-item.open .faq-answer {
      max-height: 200px;
      padding-top: 16px;
      background: rgba(248,249,250,0.5);
    }

    /* 表单 */
    .contact-form {
      background: var(--anodized-black);
      padding: 80px 0;
    }

    .input-line {
      background: transparent;
      border: none;
      border-bottom: 1px solid var(--cold-silver);
      padding: 16px 0;
      width: 100%;
      color: white;
      font-size: 16px;
      outline: none;
      transition: border 0.2s;
    }

    .input-line:focus {
      border-bottom: 2px solid var(--forge-orange);
    }

    .submit-full {
      width: 100%;
      background: var(--forge-orange);
      color: white;
      border: none;
      padding: 18px;
      font-weight: 600;
      cursor: pointer;
      margin-top: 24px;
      transition: background 0.2s;
    }

    footer {
      text-align: center;
      padding: 32px;
      color: #9CA3AF;
      font-size: 14px;
      background: var(--bg-light);
    }

    /* 响应式 */
    @media (max-width: 1024px) {
      h1 { font-size: 42px; }
      .kpi-grid { grid-template-columns: repeat(2,1fr); }
      .service-matrix { grid-template-columns: 1fr; }
      .comparison-split { grid-template-columns: 1fr; }
    }

    @media (max-width: 768px) {
      .side-nav { display: none; }
      .main-content { margin-left: 0; width: 100%; }
      .mobile-bottom-nav { display: flex; }
      section { padding: 80px 0; }
      .container { padding: 0 24px; }
      h1 { font-size: 36px; }
      h2 { font-size: 30px; }
      .faq-grid { grid-template-columns: 1fr; }
      .kpi-grid { grid-template-columns: 1fr; }
    }