/* roulang page: index */
/* ----- 全局变量与重置 ----- */
    :root {
      --bg-deep: #0A0E17;
      --bg-darker: #060A10;
      --red: #E63946;
      --red-hover: #FF4D5A;
      --white: #F1FAEE;
      --gray-blue: #1D2636;
      --gray-blue-light: #222D3F;
      --cyan: #00B4D8;
      --text-light: #B0B8C1;
      --text-muted: #6B7280;
      --border-light: rgba(241, 250, 238, 0.08);
      --border-focus: rgba(230, 57, 70, 0.8);
      --shadow-card: 0 4px 20px rgba(0,0,0,0.4);
      --shadow-card-hover: 0 8px 30px rgba(0,0,0,0.6);
      --radius-card: 8px;
      --radius-btn: 4px;
      --radius-input: 4px;
      --font-sans: "PingFang SC", "Microsoft YaHei", "Hiragino Sans GB", "Noto Sans CJK SC", sans-serif;
      --font-mono: "Inter", "SF Pro Display", system-ui, -apple-system, sans-serif;
      --container-max: 1280px;
      --nav-height: 72px;
      --section-padding: 100px;
    }
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }
    html {
      scroll-behavior: smooth;
      background-color: var(--bg-deep);
    }
    body {
      font-family: var(--font-sans);
      color: var(--text-light);
      background-color: var(--bg-deep);
      line-height: 1.75;
      font-size: 16px;
      -webkit-font-smoothing: antialiased;
      display: flex;
      flex-direction: column;
      min-height: 100vh;
    }
    img {
      max-width: 100%;
      height: auto;
      display: block;
    }
    a {
      text-decoration: none;
      color: inherit;
      transition: color 0.2s, background-color 0.2s;
    }
    button, .btn {
      cursor: pointer;
      border: none;
      background: none;
      font-family: inherit;
    }
    input, select, textarea {
      font-family: inherit;
      font-size: 16px;
      outline: none;
      transition: border 0.2s;
    }
    .container {
      max-width: var(--container-max);
      margin: 0 auto;
      padding-left: 24px;
      padding-right: 24px;
      width: 100%;
    }
    /* 移动优先边距 */
    @media (max-width: 767px) {
      .container {
        padding-left: 16px;
        padding-right: 16px;
      }
    }
    section {
      padding-top: var(--section-padding);
      padding-bottom: var(--section-padding);
    }
    @media (max-width: 767px) {
      :root {
        --section-padding: 60px;
      }
    }
    h1, h2, h3, h4 {
      color: #FFFFFF;
      font-weight: 700;
    }
    h1 {
      font-size: 48px;
      line-height: 1.2;
      font-weight: 800;
      letter-spacing: -0.5px;
    }
    h2 {
      font-size: 36px;
      line-height: 1.3;
      font-weight: 700;
    }
    h3 {
      font-size: 22px;
      line-height: 1.4;
      font-weight: 600;
    }
    h4 {
      font-size: 18px;
      line-height: 1.5;
      font-weight: 600;
    }
    @media (max-width: 767px) {
      h1 { font-size: 40px; }
      h2 { font-size: 30px; }
      h3 { font-size: 20px; }
    }
    p {
      color: var(--text-light);
      margin-bottom: 1.2em;
    }
    .text-muted {
      color: var(--text-muted);
    }
    .section-label {
      font-size: 14px;
      color: var(--cyan);
      text-transform: uppercase;
      letter-spacing: 1px;
      display: flex;
      align-items: center;
      gap: 8px;
      margin-bottom: 8px;
      font-weight: 600;
    }
    .section-label::before {
      content: "";
      display: inline-block;
      width: 24px;
      height: 2px;
      background-color: var(--red);
    }
    /* 按钮系统 */
    .btn {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      font-weight: 700;
      font-size: 16px;
      letter-spacing: 1px;
      border-radius: var(--radius-btn);
      padding: 14px 32px;
      transition: all 0.2s ease;
      text-align: center;
      white-space: nowrap;
    }
    .btn-primary {
      background-color: var(--red);
      color: white;
      border: none;
    }
    .btn-primary:hover {
      background-color: var(--red-hover);
      transform: scale(0.98);
    }
    .btn-outline {
      background: transparent;
      border: 1.5px solid var(--white);
      color: var(--white);
    }
    .btn-outline:hover {
      background: rgba(255,255,255,0.05);
      border-color: white;
    }
    .btn-text {
      background: transparent;
      border: none;
      padding: 8px 0;
      color: var(--cyan);
      font-weight: 600;
      font-size: 16px;
      transition: 0.2s;
      display: inline-flex;
      align-items: center;
    }
    .btn-text:hover {
      color: var(--red);
      transform: translateX(4px);
    }
    @media (max-width: 520px) {
      .btn {
        padding: 12px 24px;
        font-size: 15px;
      }
    }
    /* 卡片基础 */
    .card {
      background: var(--gray-blue);
      border-radius: var(--radius-card);
      box-shadow: var(--shadow-card);
      padding: 32px;
      transition: all 0.25s ease;
      height: 100%;
      border: 1px solid transparent;
    }
    .card:hover {
      box-shadow: var(--shadow-card-hover);
      transform: translateY(-4px);
      background: var(--gray-blue-light);
    }
    /* 装饰线 */
    .accent-line {
      width: 100%;
      height: 1px;
      background: rgba(255,255,255,0.04);
      margin: 24px 0;
    }

/* ----- 导航 ----- */
    #header {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: var(--nav-height);
      background: transparent;
      z-index: 999;
      transition: background 0.3s, border-bottom 0.3s;
      display: flex;
      align-items: center;
      backdrop-filter: blur(0px);
    }
    #header.scrolled {
      background: #0A0E17;
      border-bottom: 1px solid rgba(255,255,255,0.08);
      backdrop-filter: blur(8px);
    }
    .nav-container {
      display: flex;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      max-width: var(--container-max);
      margin: 0 auto;
      padding: 0 24px;
    }
    .logo {
      display: flex;
      flex-direction: column;
      font-weight: 800;
      color: #FFFFFF;
      line-height: 1.2;
      letter-spacing: 0.02em;
    }
    .logo-cn {
      font-size: 22px;
      color: #FFFFFF;
    }
    .logo-en {
      font-size: 14px;
      color: var(--text-light);
      font-family: var(--font-mono);
      letter-spacing: 1px;
    }
    .nav-links {
      display: flex;
      gap: 32px;
      align-items: center;
    }
    .nav-links a {
      color: var(--text-light);
      font-weight: 500;
      position: relative;
      padding: 8px 0;
      font-size: 16px;
      transition: color 0.2s;
    }
    .nav-links a:hover,
    .nav-links a.active {
      color: #FFFFFF;
    }
    .nav-links a::after {
      content: "";
      position: absolute;
      bottom: 0;
      left: 0;
      width: 100%;
      height: 2px;
      background: var(--red);
      transform: scaleX(0);
      transition: transform 0.2s;
    }
    .nav-links a:hover::after,
    .nav-links a.active::after {
      transform: scaleX(1);
    }
    .nav-cta {
      margin-left: 16px;
    }
    .menu-toggle {
      display: none;
      background: none;
      border: none;
      width: 28px;
      height: 20px;
      flex-direction: column;
      justify-content: space-between;
      cursor: pointer;
    }
    .menu-toggle span {
      display: block;
      height: 2px;
      background: white;
      transition: 0.3s;
    }
    @media (max-width: 1024px) {
      .nav-links {
        gap: 20px;
      }
    }
    @media (max-width: 767px) {
      .nav-links {
        display: none;
      }
      .menu-toggle {
        display: flex;
      }
      .nav-container {
        padding: 0 16px;
      }
      .mobile-menu {
        position: fixed;
        top: 0;
        left: 0;
        width: 100%;
        height: 100vh;
        background: #0A0E17;
        display: flex;
        flex-direction: column;
        align-items: center;
        justify-content: center;
        gap: 40px;
        z-index: 1000;
        transform: translateX(100%);
        transition: transform 0.3s ease;
      }
      .mobile-menu.open {
        transform: translateX(0);
      }
      .mobile-menu a {
        font-size: 22px;
        color: white;
      }
      .close-menu {
        position: absolute;
        top: 24px;
        right: 24px;
        background: none;
        color: white;
        font-size: 32px;
        border: none;
      }
    }