<style>
    :root { 
      --maxw: 880px;
      --primary: #2563eb;
      --primary-dark: #1e40af;
      --border: #e5e7eb;
      --bg-light: #f9fafb;
    }
    * { box-sizing: border-box; }
    body { 
      margin: 0; 
      font-family: system-ui, -apple-system, sans-serif; 
      color: #222; 
      line-height: 1.6;
    }
    
    /* Navigation */
    nav {
      border-bottom: 1px solid var(--border);
      padding: 16px 24px;
      position: sticky;
      top: 0;
      background: white;
      z-index: 100;
    }
    nav .container {
      max-width: var(--maxw);
      margin: 0 auto;
      display: flex;
      justify-content: space-between;
      align-items: center;
    }
    nav .brand {
      font-weight: 600;
      font-size: 18px;
      text-decoration: none;
      color: #222;
    }
    nav ul {
      list-style: none;
      margin: 0;
      padding: 0;
      display: flex;
      gap: 24px;
    }
    nav a {
      text-decoration: none;
      color: #666;
      transition: color 0.2s;
    }
    nav a:hover { color: var(--primary); }
    
    /* Sections */
    section {
      padding: 64px 24px;
    }
    .container {
      max-width: var(--maxw);
      margin: 0 auto;
    }
    
    /* Hero */
    .hero {
      text-align: center;
      padding: 96px 24px 64px;
    }
    .logo {
      width: 160px;
      height: auto;
      margin-bottom: 24px;
    }
    h1 {
      margin: 0 0 16px;
      font-size: clamp(32px, 5vw, 48px);
      font-weight: 700;
    }
    .subtitle {
      font-size: 20px;
      color: #666;
      margin: 0 auto 32px;
      max-width: 600px;
    }
    
    /* Buttons */
    .btn {
      display: inline-block;
      padding: 12px 24px;
      border-radius: 8px;
      text-decoration: none;
      font-weight: 500;
      transition: all 0.2s;
    }
    .btn-primary {
      background: var(--primary);
      color: white;
      border: 2px solid var(--primary);
    }
    .btn-primary:hover {
      background: var(--primary-dark);
      border-color: var(--primary-dark);
    }
    .btn-secondary {
      background: white;
      color: #222;
      border: 2px solid #222;
    }
    .btn-secondary:hover {
      background: #222;
      color: white;
    }
    .btn-group {
      display: flex;
      gap: 12px;
      justify-content: center;
      flex-wrap: wrap;
    }
    
    /* Course Cards */
    h2 {
      font-size: 32px;
      margin: 0 0 16px;
      text-align: center;
    }
    .section-intro {
      text-align: center;
      color: #666;
      margin-bottom: 48px;
    }
    .courses-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
      gap: 24px;
      margin-top: 32px;
    }
    .course-card {
      border: 1px solid var(--border);
      border-radius: 12px;
      padding: 32px 24px;
      text-align: center;
      transition: transform 0.2s, box-shadow 0.2s;
      background: white;
    }
    .course-card:hover {
      transform: translateY(-4px);
      box-shadow: 0 12px 24px rgba(0,0,0,0.1);
    }
    .course-icon {
      font-size: 48px;
      margin-bottom: 16px;
    }
    .course-card h3 {
      margin: 0 0 8px;
      font-size: 22px;
    }
    .course-card p {
      color: #666;
      margin: 0 0 16px;
      font-size: 15px;
    }
    .badge {
      display: inline-block;
      padding: 4px 12px;
      background: var(--bg-light);
      border-radius: 12px;
      font-size: 13px;
      color: var(--primary);
      font-weight: 500;
      margin-top: 8px;
    }
    .badge.coming-soon {
      color: #6b7280;
    }
    
    /* Features */
    .features {
      background: var(--bg-light);
    }
    .features-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
      gap: 32px;
      margin-top: 48px;
    }
    .feature {
      text-align: center;
    }
    .feature-icon {
      font-size: 40px;
      margin-bottom: 16px;
    }
    .feature h3 {
      margin: 0 0 8px;
      font-size: 20px;
    }
    .feature p {
      color: #666;
      margin: 0;
      font-size: 15px;
    }
    
    /* Footer */
    footer {
      text-align: center;
      padding: 32px 24px;
      color: #666;
      font-size: 14px;
      border-top: 1px solid var(--border);
    }
    
    /* Page transitions */
    .page {
      display: none;
    }
    .page.active {
      display: block;
    }
    
    /* Course Detail Page */
    .course-header {
      background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
      color: white;
      padding: 64px 24px;
      text-align: center;
    }
    .course-header h1 {
      color: white;
      margin-bottom: 16px;
    }
    .course-header .subtitle {
      color: rgba(255,255,255,0.9);
    }
    .course-content {
      padding: 48px 24px;
    }
    .course-content h3 {
      font-size: 24px;
      margin: 32px 0 16px;
    }
    .course-content h3:first-child {
      margin-top: 0;
    }
    .course-content ul {
      padding-left: 24px;
    }
    .course-content li {
      margin-bottom: 8px;
    }
    .info-box {
      background: var(--bg-light);
      border-left: 4px solid var(--primary);
      padding: 24px;
      border-radius: 8px;
      margin: 32px 0;
    }
    .info-box h4 {
      margin: 0 0 12px;
      font-size: 18px;
    }
    .info-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
      gap: 16px;
    }
    .info-item {
      display: flex;
      align-items: center;
      gap: 8px;
    }
    .info-item strong {
      color: #666;
      font-size: 14px;
    }
    
    @media (max-width: 640px) {
      nav ul {
        gap: 16px;
        font-size: 14px;
      }
      .btn-group {
        flex-direction: column;
        width: 100%;
      }
      .btn {
        width: 100%;
      }
    }
  </style>