/* roulang page: index */
/* 设计变量与全局重置 */
    :root {
      --primary: #F15A24;
      --primary-hover: #D1431E;
      --accent: #00C2BA;
      --bg-dark: #1E1E1E;
      --bg-card: #2A2A2A;
      --bg-form: #1A1A1A;
      --bg-nav: #1A1A1A;
      --text-primary: #FFFFFF;
      --text-secondary: #B0B0B0;
      --text-muted: #707070;
      --border-light: #333333;
      --border-input: #444444;
      --radius-card: 12px;
      --radius-btn: 8px;
      --radius-input: 6px;
      --radius-tag: 4px;
      --shadow-card: 0 4px 24px rgba(0,0,0,0.4);
      --shadow-hover: 0 8px 32px rgba(0,0,0,0.6);
      --font-title: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", sans-serif;
      --font-mono: "SF Mono", "Menlo", "Consolas", monospace;
      --nav-width: 240px;
      --header-height: 60px;
    }
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }
    html {
      scroll-behavior: smooth;
      font-size: 16px;
    }
    body {
      font-family: var(--font-title);
      background-color: var(--bg-dark);
      color: var(--text-primary);
      line-height: 1.7;
      -webkit-font-smoothing: antialiased;
      display: flex;
      min-height: 100vh;
    }
    a {
      text-decoration: none;
      color: inherit;
      transition: color 0.2s ease;
    }
    img {
      max-width: 100%;
      display: block;
    }
    button, input, textarea {
      font-family: inherit;
      outline: none;
    }
    /* 左侧竖向导航（桌面端） */
    .side-nav {
      position: fixed;
      top: 0;
      left: 0;
      width: var(--nav-width);
      height: 100vh;
      background-color: var(--bg-nav);
      border-right: 1px solid var(--border-light);
      display: flex;
      flex-direction: column;
      z-index: 1000;
      padding: 1.5rem 1rem;
      transition: transform 0.3s ease;
    }
    .logo-area {
      height: 80px;
      display: flex;
      align-items: center;
      gap: 0.5rem;
      margin-bottom: 2.5rem;
      padding-left: 0.5rem;
    }
    .logo-icon {
      width: 32px;
      height: 32px;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .logo-text {
      font-size: 24px;
      font-weight: 700;
      color: var(--primary);
      letter-spacing: -0.5px;
    }
    .nav-menu {
      list-style: none;
      display: flex;
      flex-direction: column;
      gap: 0.5rem;
      flex: 1;
    }
    .nav-item {
      position: relative;
      padding: 0.75rem 0.5rem;
      font-size: 16px;
      font-weight: 500;
      color: var(--text-secondary);
      border-left: 3px solid transparent;
      transition: all 0.2s ease;
      cursor: pointer;
      border-radius: 0 4px 4px 0;
    }
    .nav-item:hover {
      color: #FFFFFF;
      border-left-color: var(--primary);
      background: rgba(255,255,255,0.03);
    }
    .nav-item.active {
      color: #FFFFFF;
      border-left-color: var(--accent);
      background: rgba(0,194,186,0.08);
    }
    .nav-cta {
      margin-top: auto;
      background: var(--primary);
      color: white;
      text-align: center;
      padding: 0.9rem;
      border-radius: 6px;
      font-weight: 600;
      border-left: none;
      transition: background 0.2s ease, transform 0.1s ease;
      margin-bottom: 1rem;
    }
    .nav-cta:hover {
      background: var(--primary-hover);
      border-left: none;
      transform: scale(1.02);
    }
    /* 移动端顶部导航 */
    .mobile-header {
      display: none;
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: var(--header-height);
      background: var(--bg-nav);
      border-bottom: 1px solid var(--border-light);
      z-index: 1100;
      align-items: center;
      justify-content: space-between;
      padding: 0 1.25rem;
    }
    .mobile-logo {
      font-size: 22px;
      font-weight: 700;
      color: var(--primary);
      display: flex;
      align-items: center;
      gap: 0.4rem;
    }
    .hamburger {
      font-size: 26px;
      background: none;
      border: none;
      color: var(--text-primary);
      cursor: pointer;
      width: 40px;
      height: 40px;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .mobile-menu-overlay {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: var(--bg-dark);
      z-index: 1050;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 2rem;
      font-size: 20px;
      transform: translateX(100%);
      transition: transform 0.3s ease;
      list-style: none;
    }
    .mobile-menu-overlay.open {
      transform: translateX(0);
    }
    .mobile-menu-overlay a {
      color: var(--text-secondary);
      font-weight: 500;
    }
    .mobile-menu-overlay a:hover {
      color: white;
    }
    .mobile-menu-overlay .mobile-cta {
      background: var(--primary);
      color: white;
      padding: 0.8rem 2rem;
      border-radius: 8px;
    }
    /* 主内容区 */
    .main-content {
      margin-left: var(--nav-width);
      width: 100%;
      min-height: 100vh;
    }
    .container {
      max-width: 1200px;
      margin: 0 auto;
      padding: 0 2rem;
    }
    section {
      padding: 5rem 0;
    }
    /* 排版 */
    h1 {
      font-size: 48px;
      line-height: 1.3;
      font-weight: 700;
      letter-spacing: -0.5px;
    }
    h2 {
      font-size: 32px;
      line-height: 1.3;
      font-weight: 600;
      margin-bottom: 1.5rem;
      display: flex;
      align-items: center;
      gap: 0.75rem;
    }
    h3 {
      font-size: 20px;
      line-height: 1.4;
      font-weight: 600;
      margin-bottom: 0.75rem;
    }
    p {
      color: var(--text-secondary);
      margin-bottom: 1.5rem;
    }
    .section-desc {
      font-size: 18px;
      color: var(--text-muted);
      max-width: 700px;
      margin-bottom: 2.5rem;
    }
    /* 卡片与网格 */
    .grid-4, .grid-3, .grid-2 {
      display: grid;
      gap: 2rem;
    }
    .grid-4 { grid-template-columns: repeat(4, 1fr); }
    .grid-3 { grid-template-columns: repeat(3, 1fr); }
    .grid-2 { grid-template-columns: repeat(2, 1fr); }
    .card {
      background: var(--bg-card);
      border-radius: var(--radius-card);
      padding: 1.8rem;
      box-shadow: var(--shadow-card);
      border-bottom: 3px solid var(--primary);
      transition: all 0.3s ease;
    }
    .card:hover {
      transform: translateY(-4px);
      box-shadow: var(--shadow-hover);
      border-bottom-color: var(--accent);
    }
    /* 按钮 */
    .btn-primary {
      background: var(--primary);
      color: white;
      border: none;
      padding: 14px 32px;
      border-radius: var(--radius-btn);
      font-weight: 600;
      font-size: 16px;
      cursor: pointer;
      transition: background 0.2s, transform 0.1s;
      display: inline-block;
    }
    .btn-primary:hover {
      background: var(--primary-hover);
      transform: scale(1.03);
    }
    .btn-primary:active {
      transform: scale(0.98);
    }
    .btn-secondary {
      background: transparent;
      border: 2px solid var(--primary);
      color: var(--primary);
      padding: 12px 28px;
      border-radius: var(--radius-btn);
      font-weight: 600;
      transition: all 0.2s;
      display: inline-block;
    }
    .btn-secondary:hover {
      background: var(--primary);
      color: white;
    }
    .btn-ghost {
      background: transparent;
      border: 1px solid var(--text-muted);
      color: var(--text-secondary);
      padding: 10px 24px;
      border-radius: var(--radius-btn);
      transition: 0.2s;
    }
    .btn-ghost:hover {
      border-color: var(--accent);
      color: var(--accent);
    }
    /* 指标看板数字 */
    .metric-number {
      font-family: var(--font-mono);
      font-size: 56px;
      font-weight: 700;
      line-height: 1.1;
      color: var(--primary);
    }
    .trend-up { color: var(--accent); }
    .trend-down { color: #D1431E; }
    /* 表单 */
    .form-input {
      width: 100%;
      background: var(--bg-card);
      border: 1px solid var(--border-input);
      border-radius: var(--radius-input);
      padding: 0.9rem 1rem;
      color: white;
      font-size: 16px;
      margin-bottom: 1rem;
      transition: 0.2s;
    }
    .form-input:focus {
      border-color: var(--primary);
      box-shadow: 0 0 0 3px rgba(241,90,36,0.2);
    }
    /* FAQ */
    .faq-item {
      background: var(--bg-card);
      border-radius: 8px;
      margin-bottom: 8px;
      overflow: hidden;
    }
    .faq-question {
      padding: 1rem 1.5rem;
      font-weight: 600;
      font-size: 18px;
      display: flex;
      justify-content: space-between;
      align-items: center;
      cursor: pointer;
      user-select: none;
    }
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.3s ease, padding 0.3s;
      color: var(--text-secondary);
      font-size: 16px;
      border-top: 1px solid var(--border-light);
      padding: 0 1.5rem;
    }
    .faq-item.open .faq-answer {
      max-height: 200px;
      padding: 1rem 1.5rem;
    }
    .faq-icon {
      font-size: 24px;
      color: var(--primary);
      transition: 0.2s;
    }
    .faq-item.open .faq-icon {
      color: var(--accent);
    }
    /* 页脚 */
    .footer {
      background: #111111;
      padding: 3rem 0;
      border-top: 1px solid #222;
    }
    .back-to-top {
      background: var(--primary);
      width: 44px;
      height: 44px;
      border-radius: 50%;
      display: flex;
      align-items: center;
      justify-content: center;
      color: white;
      font-size: 20px;
      transition: 0.2s;
    }
    .back-to-top:hover {
      background: var(--primary-hover);
    }
    /* 响应式 */
    @media (max-width: 1024px) {
      .side-nav { display: none; }
      .mobile-header { display: flex; }
      .main-content { margin-left: 0; padding-top: var(--header-height); }
      .grid-4 { grid-template-columns: repeat(2, 1fr); }
      .grid-3 { grid-template-columns: 1fr; }
      .grid-2 { grid-template-columns: 1fr; }
      h1 { font-size: 36px; }
      h2 { font-size: 26px; }
    }
    @media (max-width: 768px) {
      .grid-4, .grid-3, .grid-2 { grid-template-columns: 1fr; }
      .container { padding: 0 1.25rem; }
      h1 { font-size: 30px; }
      .metric-number { font-size: 40px; }
      .card:hover { transform: none; }
    }
    .accent-line {
      width: 4px;
      height: 32px;
      background: var(--accent);
      display: inline-block;
      border-radius: 2px;
    }
    .vs-badge {
      background: var(--primary);
      color: white;
      width: 48px;
      height: 48px;
      border-radius: 50%;
      display: flex;
      align-items: center;
      justify-content: center;
      font-weight: 700;
      font-size: 18px;
      margin: 0 auto;
    }
    .glow-right {
      box-shadow: 0 0 20px rgba(0,194,186,0.15);
    }