:root {
    --primary: #001f3f;
    --secondary: #004080;
    --accent: #FFD700;
    --light: #f8f9fa;
    --dark: #212529;
    --success: #28a745;
    --info: #17a2b8;
    --warning: #ffc107;
    --danger: #dc3545;
  }

  @import url('https://fonts.googleapis.com/css2?family=Roboto:wght@300;400;700&family=Open+Sans:wght@400;600&display=swap');

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

  body {
    font-family: 'Open Sans', sans-serif;
    color: var(--dark);
    line-height: 1.6;
    background: linear-gradient(135deg, #f5f7fa 0%, #e4e8eb 100%);
    min-height: 100%;
    overflow-x: hidden;
  }

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

  .header {
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    color: white;
    padding: 2rem 0;
    position: relative;
    overflow: hidden;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  }

  .header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: url('https://images.gptkong.com/demo/sample3.png') center/cover no-repeat;
    opacity: 0.1;
    z-index: 0;
  }

  .header-content {
    position: relative;
    z-index: 1;
    text-align: center;
    padding: 2rem;
  }

  .header h1 {
    font-family: 'Roboto', sans-serif;
    font-size: 2.5rem;
    margin-bottom: 1rem;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
  }

  .header p {
    font-size: 1.2rem;
    max-width: 800px;
    margin: 0 auto 2rem;
  }

  .notice {
    background-color: var(--accent);
    color: var(--primary);
    padding: 1rem;
    text-align: center;
    font-weight: bold;
    margin-bottom: 2rem;
    border-radius: 4px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  }

  .article-container {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
    padding: 2rem 0;
  }

  article {
    background: white;
    border-radius: 8px;
    padding: 2rem;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
    position: relative;
    overflow: hidden;
  }

  article::after {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    width: 100px;
    height: 100px;
    background: url('https://images.gptkong.com/demo/sample6.png') center/contain no-repeat;
    opacity: 0.1;
    z-index: 0;
  }

  article h2 {
    font-family: 'Roboto', sans-serif;
    color: var(--primary);
    font-size: 1.8rem;
    margin-bottom: 1.5rem;
    position: relative;
    z-index: 1;
  }

  article h3 {
    font-family: 'Roboto', sans-serif;
    color: var(--secondary);
    font-size: 1.4rem;
    margin: 2rem 0 1rem;
    position: relative;
    z-index: 1;
  }

  article p {
    margin-bottom: 1.5rem;
    position: relative;
    z-index: 1;
  }

  article .highlight {
    color: var(--accent);
    font-weight: 600;
  }

  pre {
    background: #f5f5f5;
    border-radius: 6px;
    padding: 1.5rem;
    margin: 1.5rem 0;
    overflow: auto;
    position: relative;
    z-index: 1;
    border-left: 4px solid var(--accent);
  }

  code {
    font-family: 'Courier New', monospace;
    color: #333;
  }

  .image-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
    margin: 2rem 0;
  }

  .image-card {
    background: white;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
  }

  .image-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.15);
  }

  .image-card img {
    width: 100%;
    height: auto;
    display: block;
    border-radius: 8px 8px 0 0;
  }

  .image-card .caption {
    padding: 1rem;
    text-align: center;
    background: linear-gradient(to right, var(--primary), var(--secondary));
    color: white;
  }

  .nav-tabs {
    display: flex;
    flex-wrap: wrap;
    margin-bottom: 2rem;
    border-bottom: 1px solid #dee2e6;
  }

  .nav-tabs .tab {
    padding: 0.75rem 1.5rem;
    cursor: pointer;
    border: 1px solid transparent;
    border-bottom: none;
    border-radius: 4px 4px 0 0;
    margin-right: 0.5rem;
    transition: all 0.3s ease;
  }

  .nav-tabs .tab.active {
    background: white;
    border-color: #dee2e6 #dee2e6 white;
    color: var(--primary);
    font-weight: bold;
  }

  .tab-content {
    display: none;
    padding: 1.5rem;
    background: white;
    border-radius: 0 0 4px 4px;
    border: 1px solid #dee2e6;
    border-top: none;
  }

  .tab-content.active {
    display: block;
  }

  .accordion {
    margin: 2rem 0;
  }

  .accordion-item {
    margin-bottom: 0.5rem;
    border-radius: 4px;
    overflow: hidden;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
  }

  .accordion-header {
    padding: 1rem 1.5rem;
    background: linear-gradient(to right, var(--primary), var(--secondary));
    color: white;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: background 0.3s ease;
  }

  .accordion-header:hover {
    background: linear-gradient(to right, var(--secondary), var(--primary));
  }

  .accordion-content {
    padding: 1rem 1.5rem;
    background: white;
    display: none;
  }

  .accordion-item.active .accordion-content {
    display: block;
  }

  .footer {
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    color: white;
    padding: 2rem 0;
    text-align: center;
    margin-top: 3rem;
  }

  .footer p {
    margin-bottom: 0;
  }

  @media (max-width: 768px) {
    .header h1 {
      font-size: 2rem;
    }
    
    .header p {
      font-size: 1rem;
    }
    
    article {
      padding: 1.5rem;
    }
    
    article h2 {
      font-size: 1.5rem;
    }
    
    article h3 {
      font-size: 1.2rem;
    }
    
    pre {
      padding: 1rem;
    }
  }

  @media (max-width: 576px) {
    .header h1 {
      font-size: 1.8rem;
    }
    
    .nav-tabs .tab {
      padding: 0.5rem 1rem;
      font-size: 0.9rem;
    }
  }

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

  .animated {
    animation: fadeIn 0.8s ease-out forwards;
  }

  .delay-1 { animation-delay: 0.2s; }
  .delay-2 { animation-delay: 0.4s; }
  .delay-3 { animation-delay: 0.6s; }

  /* Tooltip */
  .tooltip {
    position: relative;
    display: inline-block;
    border-bottom: 1px dotted var(--accent);
    cursor: help;
  }

  .tooltip .tooltiptext {
    visibility: hidden;
    width: 200px;
    background-color: var(--dark);
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 5px;
    position: absolute;
    z-index: 1;
    bottom: 125%;
    left: 50%;
    transform: translateX(-50%);
    opacity: 0;
    transition: opacity 0.3s;
  }

  .tooltip:hover .tooltiptext {
    visibility: visible;
    opacity: 1;
  }