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

    html {
      scroll-behavior: smooth;
    }

    body {
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", Arial, sans-serif;
      background: #f6f8fb;
      color: #1f2937;
      line-height: 1.8;
      padding-bottom: 76px;
    }

    a {
      color: inherit;
      text-decoration: none;
    }

    .bt-container {
      max-width: 1200px;
      margin: 0 auto;
      padding: 0 18px;
    }

    .bt-topbar {
      background: #101827;
      color: #fff;
      font-size: 14px;
      padding: 8px 0;
    }

    .bt-topbar-inner {
      display: flex;
      justify-content: space-between;
      align-items: center;
      gap: 12px;
      flex-wrap: wrap;
    }

    .bt-header {
      position: sticky;
      top: 0;
      z-index: 100;
      background: #fff;
      border-bottom: 1px solid #e5e7eb;
      box-shadow: 0 8px 20px rgba(15, 23, 42, 0.04);
    }

    .bt-header-inner {
      height: 68px;
      display: flex;
      align-items: center;
      justify-content: space-between;
    }

    .bt-logo {
      display: flex;
      align-items: center;
      gap: 10px;
      font-weight: 800;
      font-size: 22px;
      color: #111827;
    }

    .bt-logo-icon {
      width: 38px;
      height: 38px;
      border-radius: 12px;
      background: linear-gradient(135deg, #f59e0b, #facc15);
      color: #111827;
      display: flex;
      align-items: center;
      justify-content: center;
      font-weight: 900;
    }

    .bt-nav {
      display: flex;
      align-items: center;
      gap: 18px;
      font-size: 15px;
      color: #374151;
    }

    .bt-nav a:hover {
      color: #d97706;
    }

    .bt-menu-btn {
      display: none;
      border: none;
      background: #f3f4f6;
      color: #111827;
      padding: 8px 12px;
      border-radius: 8px;
      font-size: 15px;
    }

    .bt-hero {
      background:
        radial-gradient(circle at top left, rgba(251, 191, 36, 0.28), transparent 35%),
        linear-gradient(135deg, #111827 0%, #1f2937 58%, #374151 100%);
      color: #fff;
      padding: 76px 0 64px;
    }

    .bt-hero-grid {
      display: grid;
      grid-template-columns: 1.12fr 0.88fr;
      gap: 40px;
      align-items: center;
    }

    .bt-badge {
      display: inline-flex;
      align-items: center;
      gap: 8px;
      background: rgba(255, 255, 255, 0.12);
      border: 1px solid rgba(255, 255, 255, 0.22);
      color: #fde68a;
      padding: 6px 14px;
      border-radius: 999px;
      font-size: 14px;
      margin-bottom: 18px;
    }

    .bt-hero h1 {
      font-size: 46px;
      line-height: 1.22;
      letter-spacing: -1px;
      margin-bottom: 20px;
    }

    .bt-hero p {
      font-size: 18px;
      color: #e5e7eb;
      max-width: 720px;
      margin-bottom: 28px;
    }

    .bt-hero-actions {
      display: flex;
      flex-wrap: wrap;
      gap: 14px;
    }

    .bt-btn {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      min-height: 44px;
      padding: 10px 22px;
      border-radius: 12px;
      font-weight: 700;
      transition: 0.2s ease;
      border: 1px solid transparent;
    }

    .bt-btn-primary {
      background: #f59e0b;
      color: #111827;
    }

    .bt-btn-primary:hover {
      background: #fbbf24;
      transform: translateY(-1px);
    }

    .bt-btn-light {
      background: rgba(255, 255, 255, 0.08);
      color: #fff;
      border-color: rgba(255, 255, 255, 0.22);
    }

    .bt-btn-light:hover {
      background: rgba(255, 255, 255, 0.16);
    }

    .bt-hero-card {
      background: #fff;
      color: #111827;
      border-radius: 24px;
      padding: 26px;
      box-shadow: 0 24px 60px rgba(0, 0, 0, 0.22);
    }

    .bt-hero-card h2 {
      font-size: 22px;
      margin-bottom: 16px;
    }

    .bt-step-mini {
      display: flex;
      gap: 12px;
      padding: 14px 0;
      border-bottom: 1px solid #f1f5f9;
    }

    .bt-step-mini:last-child {
      border-bottom: none;
    }

    .bt-step-num {
      width: 32px;
      height: 32px;
      border-radius: 50%;
      background: #fef3c7;
      color: #92400e;
      display: flex;
      align-items: center;
      justify-content: center;
      font-weight: 800;
      flex-shrink: 0;
    }

    .bt-step-mini strong {
      display: block;
      margin-bottom: 2px;
    }

    .bt-step-mini span {
      color: #6b7280;
      font-size: 14px;
    }

    .bt-quick-nav {
      margin-top: -28px;
      position: relative;
      z-index: 5;
    }

    .bt-quick-nav-inner {
      background: #fff;
      border-radius: 18px;
      box-shadow: 0 16px 36px rgba(15, 23, 42, 0.08);
      display: grid;
      grid-template-columns: repeat(5, 1fr);
      overflow: hidden;
      border: 1px solid #e5e7eb;
    }

    .bt-quick-nav a {
      padding: 18px 14px;
      text-align: center;
      font-weight: 700;
      color: #374151;
      border-right: 1px solid #e5e7eb;
    }

    .bt-quick-nav a:last-child {
      border-right: none;
    }

    .bt-quick-nav a:hover {
      background: #fffbeb;
      color: #b45309;
    }

    .bt-main {
      padding: 48px 0;
    }

    .bt-section {
      background: #fff;
      border: 1px solid #e5e7eb;
      border-radius: 22px;
      padding: 34px;
      margin-bottom: 28px;
      box-shadow: 0 10px 30px rgba(15, 23, 42, 0.035);
    }

    .bt-section-title {
      margin-bottom: 20px;
    }

    .bt-section-title span {
      display: inline-block;
      color: #d97706;
      font-weight: 800;
      font-size: 14px;
      margin-bottom: 6px;
    }

    .bt-section h2 {
      font-size: 30px;
      line-height: 1.35;
      color: #111827;
    }

    .bt-section h3 {
      font-size: 21px;
      margin: 18px 0 8px;
      color: #111827;
    }

    .bt-section p {
      color: #4b5563;
      margin-bottom: 14px;
    }

    .bt-note {
      background: #fffbeb;
      border-left: 5px solid #f59e0b;
      padding: 16px 18px;
      border-radius: 12px;
      color: #78350f;
      margin: 18px 0;
    }

    .bt-grid-3 {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 18px;
      margin-top: 20px;
    }

    .bt-grid-2 {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 18px;
      margin-top: 20px;
    }

    .bt-card {
      border: 1px solid #e5e7eb;
      border-radius: 18px;
      padding: 20px;
      background: #fff;
    }

    .bt-card:hover {
      border-color: #f59e0b;
      box-shadow: 0 12px 28px rgba(245, 158, 11, 0.12);
    }

    .bt-card-icon {
      width: 42px;
      height: 42px;
      border-radius: 14px;
      background: #fef3c7;
      color: #92400e;
      display: flex;
      align-items: center;
      justify-content: center;
      font-weight: 900;
      margin-bottom: 12px;
    }

    .bt-card strong {
      display: block;
      font-size: 18px;
      color: #111827;
      margin-bottom: 8px;
    }

    .bt-card p {
      margin-bottom: 0;
      font-size: 15px;
    }

    .bt-steps {
      counter-reset: step;
      display: grid;
      gap: 16px;
      margin-top: 22px;
    }

    .bt-step {
      position: relative;
      display: grid;
      grid-template-columns: 64px 1fr;
      gap: 18px;
      padding: 22px;
      border-radius: 18px;
      background: #f9fafb;
      border: 1px solid #e5e7eb;
    }

    .bt-step::before {
      counter-increment: step;
      content: counter(step);
      width: 48px;
      height: 48px;
      border-radius: 50%;
      background: #f59e0b;
      color: #111827;
      font-weight: 900;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 20px;
    }

    .bt-step h3 {
      margin: 0 0 6px;
    }

    .bt-table-wrap {
      width: 100%;
      overflow-x: auto;
      margin-top: 18px;
      border-radius: 16px;
      border: 1px solid #e5e7eb;
    }

    table {
      width: 100%;
      border-collapse: collapse;
      min-width: 900px;
      background: #fff;
    }

    th {
      background: #111827;
      color: #fff;
      text-align: left;
      padding: 14px 16px;
      font-size: 15px;
    }

    td {
      padding: 14px 16px;
      border-bottom: 1px solid #e5e7eb;
      color: #4b5563;
      vertical-align: top;
    }

    tr:last-child td {
      border-bottom: none;
    }

    .bt-software-name {
      font-weight: 900;
      color: #111827;
      font-size: 17px;
    }

    .bt-tag {
      display: inline-block;
      margin-top: 6px;
      padding: 3px 8px;
      border-radius: 999px;
      background: #fef3c7;
      color: #92400e;
      font-size: 12px;
      font-weight: 800;
    }

    .bt-risk-list {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 14px;
      margin-top: 18px;
    }

    .bt-risk-item {
      background: #fff7ed;
      border: 1px solid #fed7aa;
      border-radius: 16px;
      padding: 16px;
      color: #7c2d12;
      font-weight: 600;
    }

    .bt-faq {
      display: grid;
      gap: 12px;
      margin-top: 18px;
    }

    .bt-faq-item {
      border: 1px solid #e5e7eb;
      border-radius: 16px;
      overflow: hidden;
      background: #fff;
    }

    .bt-faq-question {
      width: 100%;
      text-align: left;
      background: #fff;
      border: none;
      padding: 18px 20px;
      font-size: 16px;
      font-weight: 800;
      color: #111827;
      cursor: pointer;
      display: flex;
      justify-content: space-between;
      gap: 12px;
    }

    .bt-faq-question::after {
      content: "+";
      font-size: 22px;
      color: #d97706;
      line-height: 1;
    }

    .bt-faq-item.active .bt-faq-question::after {
      content: "-";
    }

    .bt-faq-answer {
      display: none;
      padding: 0 20px 18px;
      color: #4b5563;
    }

    .bt-faq-item.active .bt-faq-answer {
      display: block;
    }

    .bt-cta {
      background: linear-gradient(135deg, #111827, #374151);
      color: #fff;
      border-radius: 24px;
      padding: 38px;
      text-align: center;
      margin-top: 28px;
    }

    .bt-cta h2 {
      font-size: 30px;
      margin-bottom: 12px;
    }

    .bt-cta p {
      color: #e5e7eb;
      max-width: 760px;
      margin: 0 auto 22px;
    }

    .bt-footer {
      background: #0f172a;
      color: #cbd5e1;
      padding: 36px 0;
      font-size: 14px;
    }

    .bt-footer-grid {
      display: grid;
      grid-template-columns: 1.2fr 0.8fr 0.8fr;
      gap: 30px;
    }

    .bt-footer h3 {
      color: #fff;
      margin-bottom: 12px;
    }

    .bt-footer a {
      display: block;
      margin-bottom: 8px;
      color: #cbd5e1;
    }

    .bt-footer a:hover {
      color: #fbbf24;
    }

    .bt-bottom-bar {
      position: fixed;
      left: 0;
      right: 0;
      bottom: 0;
      z-index: 200;
      background: #111827;
      color: #fff;
      box-shadow: 0 -10px 24px rgba(0, 0, 0, 0.18);
    }

    .bt-bottom-inner {
      max-width: 1200px;
      margin: 0 auto;
      padding: 10px 18px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 14px;
    }

    .bt-bottom-text {
      font-weight: 700;
    }

    .bt-bottom-text span {
      color: #fbbf24;
    }

    .bt-bottom-actions {
      display: flex;
      gap: 10px;
      flex-shrink: 0;
    }

    .bt-bottom-actions a {
      padding: 9px 16px;
      border-radius: 999px;
      font-weight: 800;
      font-size: 14px;
    }

    .bt-bottom-actions .bt-guide {
      background: #f59e0b;
      color: #111827;
    }

    .bt-bottom-actions .bt-safe {
      background: #374151;
      color: #fff;
    }

    .bt-backtop {
      position: fixed;
      right: 18px;
      bottom: 92px;
      width: 44px;
      height: 44px;
      border-radius: 50%;
      background: #f59e0b;
      color: #111827;
      display: flex;
      align-items: center;
      justify-content: center;
      font-weight: 900;
      box-shadow: 0 10px 24px rgba(0, 0, 0, 0.16);
      z-index: 180;
    }

    @media (max-width: 900px) {
      .bt-header-inner {
        height: auto;
        padding: 12px 0;
        flex-wrap: wrap;
      }

      .bt-menu-btn {
        display: block;
      }

      .bt-nav {
        display: none;
        width: 100%;
        flex-direction: column;
        align-items: flex-start;
        gap: 0;
        padding-top: 12px;
      }

      .bt-nav.active {
        display: flex;
      }

      .bt-nav a {
        width: 100%;
        padding: 12px 0;
        border-top: 1px solid #e5e7eb;
      }

      .bt-hero {
        padding: 52px 0 48px;
      }

      .bt-hero-grid {
        grid-template-columns: 1fr;
      }

      .bt-hero h1 {
        font-size: 34px;
      }

      .bt-hero p {
        font-size: 16px;
      }

      .bt-quick-nav-inner {
        grid-template-columns: repeat(2, 1fr);
      }

      .bt-quick-nav a {
        border-bottom: 1px solid #e5e7eb;
      }

      .bt-section {
        padding: 24px 18px;
      }

      .bt-section h2 {
        font-size: 25px;
      }

      .bt-grid-3,
      .bt-grid-2,
      .bt-risk-list,
      .bt-footer-grid {
        grid-template-columns: 1fr;
      }

      .bt-step {
        grid-template-columns: 1fr;
      }

      .bt-bottom-inner {
        flex-direction: column;
        align-items: stretch;
        gap: 8px;
      }

      .bt-bottom-text {
        text-align: center;
        font-size: 14px;
      }

      .bt-bottom-actions {
        justify-content: center;
      }

      .bt-bottom-actions a {
        flex: 1;
        text-align: center;
      }

      body {
        padding-bottom: 112px;
      }
    }

    @media (max-width: 480px) {
      .bt-logo {
        font-size: 18px;
      }

      .bt-hero h1 {
        font-size: 29px;
      }

      .bt-hero-actions {
        flex-direction: column;
      }

      .bt-btn {
        width: 100%;
      }

      .bt-quick-nav-inner {
        grid-template-columns: 1fr;
      }

      .bt-cta {
        padding: 28px 18px;
      }

      .bt-cta h2 {
        font-size: 24px;
      }
    }