/* roulang page: index */
:root {
      --primary: #FF4D2E;
      --primary-gradient: linear-gradient(135deg, #FF4D2E 0%, #FF7B4A 100%);
      --primary-dark: #e63e1d;
      --secondary: #0A0E17;
      --card-bg: #1A1F2A;
      --card-bg-light: #222833;
      --light-bg: #F4F6F9;
      --white: #FFFFFF;
      --text-dim: #B0B8C1;
      --text-mid: #5A6270;
      --font-sans: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", sans-serif;
      --font-mono: "JetBrains Mono", "SF Mono", "Menlo", monospace;
      --border-light: rgba(255,255,255,0.08);
      --shadow-sm: 0 4px 16px rgba(0,0,0,0.08);
      --shadow-md: 0 12px 28px rgba(0,0,0,0.15);
      --radius-card: 16px;
      --radius-btn: 8px;
      --section-padding: 120px 0;
      --container-max: 1280px;
      --animate-duration: 0.75s;
    }

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

    html {
      scroll-behavior: smooth;
      font-size: 16px;
    }

    body {
      background-color: var(--secondary);
      color: var(--white);
      font-family: var(--font-sans);
      line-height: 1.75;
      -webkit-font-smoothing: antialiased;
      overflow-x: hidden;
    }

    .container {
      max-width: var(--container-max);
      margin: 0 auto;
      padding: 0 24px;
      width: 100%;
    }

    /* 导航 styling */
    .navbar {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      z-index: 1000;
      padding: 18px 0;
      transition: background 0.3s ease, backdrop-filter 0.3s ease, box-shadow 0.3s ease;
      background-color: transparent;
      backdrop-filter: blur(0px);
      border-bottom: 1px solid transparent;
    }

    .navbar.scrolled {
      background-color: rgba(10, 14, 23, 0.92);
      backdrop-filter: blur(16px);
      border-bottom: 1px solid rgba(255,255,255,0.08);
      box-shadow: 0 8px 24px rgba(0,0,0,0.4);
    }

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

    .logo {
      font-size: 1.7rem;
      font-weight: 700;
      letter-spacing: 1px;
      color: var(--white);
      text-decoration: none;
      display: flex;
      align-items: center;
      gap: 6px;
    }
    .logo span {
      color: var(--primary);
    }

    .nav-links {
      display: flex;
      align-items: center;
      gap: 32px;
      list-style: none;
    }

    .nav-links a {
      color: var(--text-dim);
      text-decoration: none;
      font-weight: 500;
      font-size: 0.95rem;
      transition: color 0.2s;
      letter-spacing: 0.3px;
    }

    .nav-links a:hover {
      color: var(--white);
    }

    .menu-toggle {
      display: none;
      flex-direction: column;
      gap: 6px;
      cursor: pointer;
      background: none;
      border: none;
      padding: 4px;
    }
    .menu-toggle span {
      width: 28px;
      height: 2px;
      background: var(--white);
      transition: 0.25s;
      display: block;
    }

    .mobile-active .menu-toggle span:nth-child(1) { transform: rotate(45deg) translate(5px,6px); }
    .mobile-active .menu-toggle span:nth-child(2) { opacity: 0; }
    .mobile-active .menu-toggle span:nth-child(3) { transform: rotate(-45deg) translate(5px,-6px); }

    @media (max-width: 1024px) {
      .nav-links {
        position: fixed;
        top: 0;
        left: 0;
        width: 100%;
        height: 100vh;
        background: var(--secondary);
        flex-direction: column;
        justify-content: center;
        gap: 40px;
        transform: translateX(100%);
        transition: transform 0.4s cubic-bezier(0.22,0.61,0.36,1);
        opacity: 0;
        z-index: 999;
      }
      .nav-links.active {
        transform: translateX(0);
        opacity: 1;
      }
      .menu-toggle {
        display: flex;
        z-index: 1001;
      }
      .nav-links a { font-size: 1.8rem; }
    }

    /* Hero */
    .hero {
      height: 100vh;
      display: flex;
      align-items: center;
      position: relative;
      overflow: hidden;
      background-color: var(--secondary);
      padding-top: 80px;
    }
    .hero-bg {
      position: absolute;
      right: 0;
      top: 0;
      width: 55%;
      height: 100%;
      background: radial-gradient(circle at 30% 40%, rgba(255,77,46,0.08) 0%, transparent 70%);
      pointer-events: none;
    }
    .hero-content {
      display: flex;
      align-items: center;
      gap: 40px;
      position: relative;
      z-index: 2;
      width: 100%;
    }
    .hero-text {
      flex: 1;
    }
    .hero-text h1 {
      font-size: clamp(2.8rem, 5vw, 3.8rem);
      font-weight: 700;
      line-height: 1.2;
      margin-bottom: 20px;
      color: #fff;
    }
    .hero-highlight {
      color: var(--primary);
    }
    .hero-desc {
      font-size: 1.15rem;
      color: var(--text-dim);
      margin-bottom: 36px;
      max-width: 520px;
      line-height: 1.7;
    }
    .btn-group {
      display: flex;
      gap: 16px;
      flex-wrap: wrap;
    }
    .btn-primary {
      background: var(--primary-gradient);
      color: white;
      font-weight: 600;
      padding: 14px 34px;
      border-radius: var(--radius-btn);
      text-decoration: none;
      display: inline-block;
      letter-spacing: 0.4px;
      transition: transform 0.25s, box-shadow 0.25s;
      box-shadow: 0 6px 20px rgba(255,77,46,0.35);
    }
    .btn-primary:hover {
      transform: scale(1.03);
      box-shadow: 0 10px 24px rgba(255,120,60,0.45);
    }
    .btn-secondary {
      border: 1px solid rgba(255,255,255,0.3);
      color: white;
      padding: 14px 34px;
      border-radius: var(--radius-btn);
      text-decoration: none;
      font-weight: 500;
      transition: 0.2s;
      backdrop-filter: blur(2px);
    }
    .btn-secondary:hover {
      background: rgba(255,77,46,0.12);
      border-color: var(--primary);
    }

    .hero-graphic {
      flex: 1;
      display: flex;
      justify-content: center;
      opacity: 0.9;
    }
    .glow-circle {
      width: 380px;
      height: 380px;
      border-radius: 50%;
      background: radial-gradient(circle at 30% 30%, rgba(255,77,46,0.2), transparent);
      border: 1px solid rgba(255,77,46,0.15);
    }

    @media (max-width: 768px) {
      .hero {
        height: auto;
        min-height: 100vh;
        padding: 130px 0 60px;
      }
      .hero-content {
        flex-direction: column;
        text-align: center;
      }
      .hero-text h1 { font-size: 2.5rem; }
      .btn-group { justify-content: center; }
      .hero-graphic { display: none; }
    }

    section {
      padding: var(--section-padding);
    }
    @media (max-width: 768px) {
      section { padding: 80px 0; }
    }

    .section-title {
      font-size: 2.2rem;
      font-weight: 700;
      margin-bottom: 16px;
    }

    /* features */
    .features-grid {
      display: grid;
      grid-template-columns: 1.5fr 1fr;
      gap: 24px;
      margin-top: 48px;
    }
    .card {
      background: var(--card-bg);
      border-radius: var(--radius-card);
      padding: 32px;
      transition: 0.3s;
      border: 1px solid var(--border-light);
    }
    .card:hover {
      transform: translateY(-6px);
      box-shadow: var(--shadow-md);
    }
    .card-large { padding: 42px; }
    .icon-orange {
      color: var(--primary);
      font-size: 2rem;
      margin-bottom: 18px;
    }
    .card h3 { font-size: 1.5rem; margin-bottom: 10px; }
    .card p { color: var(--text-dim); }

    @media (max-width: 768px) {
      .features-grid {
        grid-template-columns: 1fr;
      }
    }

    .stats-row {
      display: grid;
      grid-template-columns: repeat(4,1fr);
      gap: 24px;
      margin-top: 40px;
    }
    .stat-item {
      text-align: center;
    }
    .stat-number {
      font-family: var(--font-mono);
      font-size: 2.8rem;
      font-weight: 700;
      color: var(--primary);
    }
    @media (max-width: 768px) {
      .stats-row { grid-template-columns: 1fr 1fr; }
    }

    .service-row {
      display: flex;
      align-items: center;
      gap: 60px;
      margin-bottom: 80px;
    }
    .service-row.reverse { flex-direction: row-reverse; }
    .service-img {
      width: 340px;
      height: 240px;
      background: #2a2e38;
      border-radius: 20px;
      object-fit: cover;
    }
    @media (max-width: 1024px) {
      .service-row, .service-row.reverse { flex-direction: column; }
    }

    .faq-list {
      max-width: 800px;
      margin-top: 30px;
    }
    .faq-item {
      border-bottom: 1px solid var(--border-light);
      padding: 18px 0;
    }
    .faq-question {
      font-weight: 600;
      cursor: pointer;
      display: flex;
      justify-content: space-between;
      font-size: 1.1rem;
    }
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.4s ease;
      color: var(--text-dim);
    }
    .faq-item.active .faq-answer { max-height: 180px; margin-top: 12px; }

    .cta-banner {
      background: #0f131c;
      text-align: center;
      padding: 80px 24px;
      border-radius: 28px;
    }