:root {
      --primary-color: #1D7BFF;
      --bg-color: #f7f9fc;
      --card-bg: #ffffff;
      --text-main: #222222;
      --text-muted: #666666;
      --border-color: #e3e8f0;
      --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    }
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body { font-family: var(--font-family); background-color: var(--bg-color); color: var(--text-main); line-height: 1.6; }
    a { color: inherit; text-decoration: none; transition: color 0.2s; }
    a:hover { color: var(--primary-color); }
    
    .site-header { background-color: var(--card-bg); border-bottom: 2px solid var(--primary-color); position: sticky; top: 0; z-index: 100; }
    .header-top { max-width: 1200px; margin: 0 auto; padding: 15px 20px; display: flex; justify-content: center; align-items: center; position: relative; }
    .logo { display: flex; align-items: center; gap: 10px; font-size: 24px; font-weight: 800; color: var(--text-main); }
    .logo img { height: 36px; }
    .menu-toggle { display: none; position: absolute; right: 20px; background: none; border: none; flex-direction: column; gap: 6px; cursor: pointer; }
    .menu-toggle span { display: block; width: 25px; height: 3px; background-color: var(--text-main); }
    .desktop-nav { border-top: 1px solid var(--border-color); background-color: #fafbfc; }
    .nav-container { max-width: 1200px; margin: 0 auto; display: flex; justify-content: center; flex-wrap: wrap; }
    .nav-container a { padding: 12px 20px; font-size: 14px; font-weight: 600; color: var(--text-muted); border-bottom: 2px solid transparent; }
    .nav-container a:hover { color: var(--primary-color); border-bottom-color: var(--primary-color); }
    .drawer-overlay { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.5); z-index: 998; display: none; }
    .mobile-drawer { position: fixed; top: 0; left: -280px; width: 280px; height: 100%; background-color: var(--card-bg); z-index: 999; transition: left 0.3s; display: flex; flex-direction: column; }
    .mobile-drawer.open { left: 0; }
    .drawer-header { padding: 20px; border-bottom: 1px solid var(--border-color); display: flex; justify-content: space-between; align-items: center; }
    .drawer-close { background: none; border: none; font-size: 24px; }
    .drawer-nav { display: flex; flex-direction: column; padding: 20px; }
    .drawer-nav a { padding: 12px 0; border-bottom: 1px solid var(--border-color); }

    .main-container { max-width: 1000px; margin: 40px auto; padding: 0 20px; }
    .download-header { text-align: center; margin-bottom: 40px; }
    .download-header h1 { font-size: 28px; color: var(--text-main); margin-bottom: 10px; }
    .download-header p { color: var(--text-muted); }

    .download-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
    .download-card { background-color: var(--card-bg); border: 1px solid var(--border-color); border-radius: 4px; padding: 25px; display: flex; flex-direction: column; }
    .download-tag { display: inline-block; align-self: flex-start; background-color: #eff6ff; color: var(--primary-color); font-size: 12px; font-weight: 700; padding: 3px 8px; border-radius: 3px; margin-bottom: 15px; }
    .download-title { font-size: 18px; font-weight: 700; margin-bottom: 10px; color: var(--text-main); }
    .download-desc { font-size: 14px; color: var(--text-muted); margin-bottom: 20px; flex-grow: 1; line-height: 1.6; }
    .download-btn { display: inline-block; text-align: center; background-color: var(--primary-color); color: #fff; padding: 10px 20px; border-radius: 4px; font-weight: 600; transition: background-color 0.2s; }
    .download-btn:hover { background-color: var(--primary-hover); color: #fff; }

    .site-footer { background-color: #1e293b; color: #94a3b8; font-size: 14px; margin-top: 50px; border-top: 3px solid var(--primary-color); }
    .footer-container { max-width: 1200px; margin: 0 auto; padding: 40px 20px; display: grid; grid-template-columns: 2fr 1fr 1fr; gap: 40px; }
    .footer-info .logo { color: #fff; margin-bottom: 15px; }
    .footer-links h4, .footer-contact h4 { color: #fff; margin-bottom: 15px; font-size: 16px; font-weight: 700; }
    .footer-links-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
    .footer-links-grid a { color: #94a3b8; }
    .friend-links { border-top: 1px solid #334155; border-bottom: 1px solid #334155; max-width: 1200px; margin: 0 auto; padding: 20px; display: flex; flex-direction: column; gap: 10px; }
    .friend-title { font-weight: 700; color: #fff; }
    .friend-content { display: flex; flex-wrap: wrap; gap: 15px; }
    .friend-content a { color: #94a3b8; }
    .footer-bottom { text-align: center; padding: 20px; background-color: #0f172a; font-size: 12px; }

    @media (max-width: 768px) {
      .desktop-nav { display: none; }
      .menu-toggle { display: flex; }
      .download-grid { grid-template-columns: 1fr; }
      .footer-container { grid-template-columns: 1fr; }
    }