:root {
    --primary: #3498db;
    --primary-dark: #2980b9;
    --secondary: #2c3e50;
    --accent: #e67e22;
    --text: #2c3e50;
    --text-light: #7f8c8d;
    --bg: #f9f9f9;
    --card-bg: #ffffff;
    --transition: all 0.3s ease;
  }

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

  body {
    font-family: 'Roboto', sans-serif;
    line-height: 1.6;
    color: var(--text);
    background: var(--bg);
    overflow-x: hidden;
  }

  .container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
  }

  .header {
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: white;
    padding: 40px 0;
    text-align: center;
    position: relative;
    overflow: hidden;
    margin-bottom: 60px;
  }

  .header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: url('https://images.gptkong.com/demo/sample1.png') center/cover no-repeat;
    opacity: 0.1;
    z-index: 0;
  }

  .header-content {
    position: relative;
    z-index: 1;
  }

  .header h1 {
    font-size: 2.5rem;
    margin-bottom: 20px;
    text-shadow: 0 2px 4px rgba(0,0,0,0.2);
  }

  .header p {
    font-size: 1.2rem;
    max-width: 800px;
    margin: 0 auto;
  }

  .design-note {
    background: var(--card-bg);
    padding: 15px;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    margin: 30px auto;
    max-width: 600px;
    text-align: center;
    font-size: 0.9rem;
    color: var(--text-light);
    border-left: 4px solid var(--accent);
  }

  article {
    background: var(--card-bg);
    border-radius: 12px;
    box-shadow: 0 8px 24px rgba(0,0,0,0.08);
    padding: 40px;
    margin-bottom: 60px;
  }

  article h2 {
    color: var(--secondary);
    font-size: 2rem;
    margin-bottom: 30px;
    position: relative;
    padding-bottom: 15px;
  }

  article h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 80px;
    height: 4px;
    background: linear-gradient(90deg, var(--primary), var(--accent));
    border-radius: 2px;
  }

  article h3 {
    color: var(--primary);
    font-size: 1.5rem;
    margin: 30px 0 20px;
  }

  article p {
    margin-bottom: 20px;
    font-size: 1.1rem;
    color: var(--text);
    line-height: 1.8;
  }

  pre {
    background: #f5f7fa;
    border-radius: 8px;
    padding: 20px;
    margin: 25px 0;
    overflow: auto;
    border-left: 4px solid var(--primary);
    font-family: 'Courier New', monospace;
    font-size: 0.95rem;
    line-height: 1.5;
  }

  code {
    font-family: 'Courier New', monospace;
    background: rgba(52, 152, 219, 0.1);
    padding: 2px 6px;
    border-radius: 4px;
    color: var(--primary-dark);
    font-size: 0.9rem;
  }

  table {
    width: 100%;
    border-collapse: collapse;
    margin: 30px 0;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    border-radius: 8px;
    overflow: hidden;
  }

  th, td {
    padding: 15px;
    text-align: left;
    border-bottom: 1px solid #eee;
  }

  th {
    background: var(--primary);
    color: white;
    font-weight: 500;
  }

  tr:nth-child(even) {
    background: #f9f9f9;
  }

  tr:hover {
    background: #f1f1f1;
  }

  .gallery {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
    margin: 40px 0;
  }

  .gallery-item {
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 8px 16px rgba(0,0,0,0.1);
    transition: var(--transition);
  }

  .gallery-item:hover {
    transform: translateY(-5px);
    box-shadow: 0 12px 24px rgba(0,0,0,0.15);
  }

  .gallery-item img {
    width: 100%;
    height: auto;
    display: block;
    transition: var(--transition);
  }

  .gallery-item:hover img {
    transform: scale(1.05);
  }

  .nav-tabs {
    display: flex;
    margin-bottom: 30px;
    border-bottom: 1px solid #eee;
  }

  .nav-tab {
    padding: 12px 24px;
    cursor: pointer;
    font-weight: 500;
    color: var(--text-light);
    transition: var(--transition);
    border-bottom: 3px solid transparent;
  }

  .nav-tab.active {
    color: var(--primary);
    border-bottom-color: var(--primary);
  }

  .nav-tab:hover {
    color: var(--primary-dark);
  }

  .tech-highlight {
    background: linear-gradient(135deg, rgba(52, 152, 219, 0.1), rgba(46, 204, 113, 0.1));
    border-radius: 12px;
    padding: 30px;
    margin: 40px 0;
    border-left: 4px solid var(--primary);
  }

  .tech-highlight h4 {
    color: var(--primary);
    margin-bottom: 15px;
    font-size: 1.3rem;
  }

  .tech-highlight p {
    color: var(--text);
  }

  footer {
    background: var(--secondary);
    color: white;
    padding: 30px 0;
    text-align: center;
    margin-top: 60px;
  }

  @media (max-width: 768px) {
    .header h1 {
      font-size: 2rem;
    }
    
    article {
      padding: 30px;
    }
    
    article h2 {
      font-size: 1.8rem;
    }
    
    article h3 {
      font-size: 1.3rem;
    }
    
    .gallery {
      grid-template-columns: 1fr;
    }
  }

  @media (max-width: 480px) {
    .header {
      padding: 30px 0;
    }
    
    .header h1 {
      font-size: 1.8rem;
    }
    
    article {
      padding: 20px;
    }
    
    article h2 {
      font-size: 1.5rem;
    }
  }

  /* Animations */
  @keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
  }

  .animate {
    animation: fadeIn 1s ease forwards;
  }

  .delay-1 {
    animation-delay: 0.2s;
  }

  .delay-2 {
    animation-delay: 0.4s;
  }

  .delay-3 {
    animation-delay: 0.6s;
  }