/* roulang page: index */
/* ----- 设计变量与全局重置 ----- */
    :root {
      --primary-bg: #0A0E17;
      --card-bg: #141A24;
      --accent-red: #E63946;
      --accent-red-hover: #ff4f5e;
      --text-white: #F8F9FA;
      --text-gray: #B0B5BD;
      --border-subtle: rgba(255, 255, 255, 0.06);
      --radius-sm: 8px;
      --radius-md: 12px;
      --shadow-card: 0 8px 30px rgba(0, 0, 0, 0.5);
      --transition-smooth: 0.25s ease;
      --font-sans: "PingFang SC", "Microsoft YaHei", "Inter", system-ui, -apple-system, sans-serif;
      --container-max: 1200px;
      --section-gap: 100px;
      --section-gap-mobile: 60px;
    }

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

    body {
      font-family: var(--font-sans);
      background-color: var(--primary-bg);
      color: var(--text-gray);
      line-height: 1.5;
      font-size: 15px;
      -webkit-font-smoothing: antialiased;
      -moz-osx-font-smoothing: grayscale;
    }

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

    a {
      text-decoration: none;
      color: inherit;
      transition: color var(--transition-smooth);
    }

    button, .btn {
      cursor: pointer;
      font-family: inherit;
      transition: all var(--transition-smooth);
      border: none;
      outline: none;
    }

    .container {
      max-width: var(--container-max);
      margin: 0 auto;
      padding: 0 20px;
    }
    @media (max-width: 768px) {
      .container {
        padding: 0 16px;
      }
    }

    /* ----- 导航系统 (沉浸式) ----- */
    .header {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      z-index: 1000;
      padding: 16px 0;
      transition: background 0.3s ease, backdrop-filter 0.3s ease, padding 0.3s ease;
      background: transparent;
    }
    .header.scrolled {
      background: rgba(10, 14, 23, 0.85);
      backdrop-filter: blur(12px);
      -webkit-backdrop-filter: blur(12px);
      padding: 12px 0;
      box-shadow: 0 4px 20px rgba(0,0,0,0.3);
    }
    .nav-container {
      display: flex;
      align-items: center;
      justify-content: space-between;
      max-width: var(--container-max);
      margin: 0 auto;
      padding: 0 20px;
    }
    .logo {
      font-size: 24px;
      font-weight: 700;
      color: var(--text-white);
      letter-spacing: -0.5px;
    }
    .logo span {
      color: var(--accent-red);
    }
    .nav-links {
      display: flex;
      align-items: center;
      gap: 32px;
    }
    .nav-links a {
      color: var(--text-gray);
      font-weight: 500;
      font-size: 15px;
      position: relative;
      padding: 4px 0;
    }
    .nav-links a:hover, .nav-links a.active {
      color: var(--text-white);
    }
    .nav-links a::after {
      content: '';
      position: absolute;
      bottom: 0;
      left: 0;
      width: 0;
      height: 2px;
      background: var(--accent-red);
      transition: width 0.25s ease;
    }
    .nav-links a:hover::after, .nav-links a.active::after {
      width: 100%;
    }
    .btn-nav {
      background: var(--accent-red);
      color: white !important;
      padding: 10px 22px !important;
      border-radius: var(--radius-sm);
      font-weight: 600;
      margin-left: 16px;
      transition: transform 0.25s ease, background 0.25s ease;
    }
    .btn-nav:hover {
      background: var(--accent-red-hover);
      transform: translateY(-2px);
    }
    .btn-nav::after {
      display: none;
    }
    .hamburger {
      display: none;
      flex-direction: column;
      cursor: pointer;
      gap: 5px;
      width: 24px;
      height: 18px;
      justify-content: center;
      z-index: 1001;
    }
    .hamburger span {
      display: block;
      height: 2px;
      background: white;
      transition: 0.3s;
      border-radius: 2px;
    }
    .hamburger.active span:nth-child(1) {
      transform: rotate(45deg) translate(5px, 5px);
    }
    .hamburger.active span:nth-child(2) {
      opacity: 0;
    }
    .hamburger.active span:nth-child(3) {
      transform: rotate(-45deg) translate(5px, -5px);
    }
    @media (max-width: 1024px) {
      .nav-links {
        gap: 20px;
      }
    }
    @media (max-width: 768px) {
      .hamburger {
        display: flex;
      }
      .nav-links {
        position: fixed;
        top: 0;
        right: -100%;
        width: 70%;
        max-width: 320px;
        height: 100vh;
        background: #0A0E17;
        flex-direction: column;
        justify-content: center;
        align-items: flex-start;
        padding: 40px;
        transition: right 0.4s ease;
        box-shadow: -10px 0 30px rgba(0,0,0,0.7);
        gap: 28px;
      }
      .nav-links.active {
        right: 0;
      }
      .nav-links a {
        font-size: 18px;
        font-weight: 500;
      }
      .btn-nav {
        margin-left: 0;
        width: 100%;
        text-align: center;
      }
    }

    /* ----- 通用板块样式 ----- */
    section {
      padding: var(--section-gap) 0;
    }
    @media (max-width: 768px) {
      section {
        padding: var(--section-gap-mobile) 0;
      }
    }
    .section-title {
      font-size: 28px;
      font-weight: 600;
      color: var(--text-white);
      margin-bottom: 16px;
      position: relative;
      display: inline-block;
    }
    .section-title::after {
      content: '';
      display: block;
      width: 40px;
      height: 2px;
      background: var(--accent-red);
      margin-top: 8px;
    }
    .center-title {
      text-align: center;
      margin-bottom: 48px;
    }
    .center-title .section-title::after {
      margin: 8px auto 0;
    }

    /* ----- 首屏 Hero ----- */
    .hero {
      min-height: 100vh;
      display: flex;
      align-items: center;
      background: var(--primary-bg);
      position: relative;
      overflow: hidden;
      padding-top: 80px;
    }
    .hero-grid {
      display: flex;
      align-items: center;
      gap: 60px;
    }
    .hero-text {
      flex: 0 0 50%;
    }
    .hero-text h1 {
      font-size: 42px;
      font-weight: 700;
      line-height: 1.2;
      color: var(--text-white);
      margin-bottom: 20px;
      letter-spacing: -0.5px;
    }
    .hero-text h1 .highlight {
      color: var(--accent-red);
    }
    .hero-sub {
      font-size: 16px;
      color: var(--text-gray);
      margin-bottom: 32px;
      max-width: 450px;
    }
    .hero-buttons {
      display: flex;
      gap: 16px;
      flex-wrap: wrap;
    }
    .btn-primary {
      background: var(--accent-red);
      color: white;
      padding: 14px 32px;
      border-radius: var(--radius-sm);
      font-weight: 600;
      font-size: 16px;
      box-shadow: 0 4px 15px rgba(230, 57, 70, 0.4);
    }
    .btn-primary:hover {
      background: var(--accent-red-hover);
      transform: translateY(-2px);
    }
    .btn-outline {
      background: transparent;
      border: 1px solid var(--text-white);
      color: var(--text-white);
      padding: 14px 32px;
      border-radius: var(--radius-sm);
      font-weight: 600;
      font-size: 16px;
    }
    .btn-outline:hover {
      background: rgba(255,255,255,0.05);
      transform: translateY(-2px);
    }
    .hero-image {
      flex: 0 0 45%;
      position: relative;
    }
    .hero-image img {
      width: 100%;
      border-radius: var(--radius-md);
      box-shadow: 0 20px 40px rgba(0,0,0,0.6);
      object-fit: cover;
    }
    @media (max-width: 768px) {
      .hero-grid {
        flex-direction: column;
        text-align: center;
      }
      .hero-text, .hero-image {
        flex: auto;
        width: 100%;
      }
      .hero-text h1 {
        font-size: 36px;
      }
      .hero-buttons {
        justify-content: center;
      }
    }

    /* ----- 核心优势 (大数字风格) ----- */
    .advantages-list {
      display: flex;
      flex-direction: column;
      gap: 40px;
      max-width: 900px;
      margin-top: 40px;
    }
    .adv-item {
      display: flex;
      align-items: flex-start;
      gap: 24px;
    }
    .adv-number {
      font-size: 48px;
      font-weight: 700;
      color: var(--accent-red);
      opacity: 0.15;
      line-height: 1;
      min-width: 70px;
    }
    .adv-content h3 {
      font-size: 20px;
      font-weight: 600;
      color: var(--text-white);
      margin-bottom: 8px;
    }
    .adv-content p {
      color: var(--text-gray);
      font-size: 15px;
      line-height: 1.6;
    }
    @media (max-width: 768px) {
      .adv-number {
        font-size: 36px;
      }
    }

    /* ----- 功能卡片 + 标签筛选 ----- */
    .filter-tags {
      display: flex;
      flex-wrap: wrap;
      gap: 12px;
      margin-bottom: 40px;
      justify-content: center;
    }
    .tag {
      padding: 8px 20px;
      border-radius: 20px;
      background: transparent;
      border: 1px solid rgba(255,255,255,0.2);
      color: var(--text-gray);
      font-weight: 500;
      cursor: pointer;
      transition: 0.2s;
    }
    .tag.active {
      background: var(--accent-red);
      border-color: var(--accent-red);
      color: white;
    }
    .features-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 24px;
    }
    .feature-card {
      background: var(--card-bg);
      border-radius: var(--radius-sm);
      padding: 28px 24px;
      transition: all 0.3s ease;
      border: 1px solid transparent;
    }
    .feature-card:hover {
      transform: translateY(-4px);
      box-shadow: var(--shadow-card);
      border-color: rgba(255,255,255,0.05);
    }
    .feature-icon {
      width: 40px;
      height: 40px;
      border: 2px solid var(--accent-red);
      border-radius: 6px;
      display: flex;
      align-items: center;
      justify-content: center;
      margin-bottom: 20px;
      color: var(--accent-red);
      font-size: 18px;
    }
    .feature-card h3 {
      color: var(--text-white);
      font-weight: 600;
      margin-bottom: 10px;
    }
    @media (max-width: 1024px) {
      .features-grid {
        grid-template-columns: repeat(2, 1fr);
      }
    }
    @media (max-width: 520px) {
      .features-grid {
        grid-template-columns: 1fr;
      }
    }

    /* ----- 使用场景 (图文交错) ----- */
    .scene-row {
      display: flex;
      align-items: center;
      gap: 50px;
      margin-bottom: 60px;
    }
    .scene-row.reverse {
      flex-direction: row-reverse;
    }
    .scene-img {
      flex: 0 0 45%;
    }
    .scene-img img {
      border-radius: var(--radius-md);
      box-shadow: 0 10px 25px rgba(0,0,0,0.5);
    }
    .scene-text {
      flex: 1;
    }
    .scene-label {
      display: inline-block;
      background: rgba(230,57,70,0.15);
      color: var(--accent-red);
      padding: 4px 12px;
      border-radius: 20px;
      font-size: 12px;
      font-weight: 600;
      margin-bottom: 12px;
    }
    .scene-text h3 {
      color: var(--text-white);
      font-size: 24px;
      margin-bottom: 12px;
    }
    @media (max-width: 768px) {
      .scene-row, .scene-row.reverse {
        flex-direction: column;
      }
    }

    /* ----- 数据背书 ----- */
    .stats-grid {
      display: flex;
      justify-content: space-around;
      text-align: center;
      margin: 30px 0;
      flex-wrap: wrap;
      gap: 30px;
    }
    .stat-number {
      font-size: 42px;
      font-weight: 700;
      color: var(--accent-red);
    }
    .stat-label {
      color: var(--text-gray);
      font-size: 14px;
    }

    /* ----- FAQ 手风琴 ----- */
    .faq-list {
      max-width: 800px;
      margin: 0 auto;
    }
    .faq-item {
      background: var(--card-bg);
      border-radius: var(--radius-sm);
      margin-bottom: 12px;
      overflow: hidden;
    }
    .faq-question {
      padding: 18px 24px;
      display: flex;
      justify-content: space-between;
      align-items: center;
      cursor: pointer;
      color: var(--text-white);
      font-weight: 500;
    }
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.3s ease;
      padding: 0 24px;
      color: var(--text-gray);
    }
    .faq-item.active .faq-answer {
      max-height: 200px;
      padding-bottom: 18px;
    }

    /* ----- CTA 横幅 & 页脚 ----- */
    .cta-banner {
      background: var(--accent-red);
      text-align: center;
      padding: 60px 20px;
      color: white;
    }
    .btn-white {
      background: white;
      color: #0A0E17;
      padding: 14px 36px;
      border-radius: var(--radius-sm);
      font-weight: 700;
      margin-top: 20px;
      display: inline-block;
    }
    .footer {
      background: #0A0E17;
      padding: 40px 0;
      text-align: center;
      border-top: 1px solid rgba(255,255,255,0.06);
      color: var(--text-gray);
    }