:root {
    --primary-blue: #1E90FF;
    --secondary-green: #32CD32;
    --accent-orange: #FFA500;
    --neutral-white: #FFFFFF;
    --neutral-gray: #A9A9A9;
    --dark-blue: #0F4C81;
    --light-blue: #E6F2FF;
    --deep-green: #228B22;
  }

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

  body {
    font-family: 'Roboto', sans-serif;
    line-height: 1.6;
    color: #333;
    background: linear-gradient(135deg, var(--light-blue), var(--neutral-white));
    min-height: 100%;
  }

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

  .header {
    background: linear-gradient(135deg, var(--primary-blue), var(--deep-green));
    color: white;
    padding: 60px 0;
    text-align: center;
    position: relative;
    overflow: hidden;
    border-bottom: 5px solid var(--accent-orange);
  }

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

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

  .header h1 {
    font-size: 2.8rem;
    margin-bottom: 20px;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
  }

  .header p {
    font-size: 1.2rem;
    max-width: 800px;
    margin: 0 auto 30px;
  }

  .notice {
    background-color: var(--neutral-white);
    color: var(--dark-blue);
    padding: 15px;
    border-radius: 8px;
    display: inline-block;
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
    font-weight: bold;
    margin-top: 20px;
  }

  .nav {
    background-color: var(--neutral-white);
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 1000;
  }

  .nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 0;
  }

  .nav-links {
    display: flex;
    gap: 30px;
  }

  .nav-link {
    color: var(--dark-blue);
    text-decoration: none;
    font-weight: 500;
    padding: 5px 10px;
    border-radius: 5px;
    transition: all 0.3s ease;
  }

  .nav-link:hover {
    color: var(--accent-orange);
    background-color: rgba(255,165,0,0.1);
  }

  .main-content {
    padding: 50px 0;
  }

  article {
    background-color: var(--neutral-white);
    border-radius: 15px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.1);
    padding: 40px;
    margin-bottom: 50px;
  }

  article h2 {
    color: var(--dark-blue);
    font-size: 2rem;
    margin-bottom: 30px;
    padding-bottom: 15px;
    border-bottom: 2px solid var(--primary-blue);
  }

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

  article p {
    margin-bottom: 20px;
    font-size: 1.1rem;
    line-height: 1.7;
  }

  pre {
    background-color: #f5f5f5;
    border-radius: 8px;
    padding: 20px;
    margin: 25px 0;
    overflow-x: auto;
    box-shadow: inset 0 0 5px rgba(0,0,0,0.1);
    border-left: 4px solid var(--accent-orange);
  }

  code {
    font-family: 'Courier New', monospace;
    font-size: 0.95rem;
    color: #333;
  }

  .image-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 25px;
    margin: 40px 0;
  }

  .image-card {
    background-color: var(--neutral-white);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 5px 15px rgba(0,0,0,0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
  }

  .image-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 15px 30px rgba(0,0,0,0.2);
  }

  .image-card img {
    width: 100%;
    height: 250px;
    object-fit: cover;
    border-bottom: 3px solid var(--primary-blue);
  }

  .image-card p {
    padding: 15px;
    text-align: center;
    color: var(--dark-blue);
    font-weight: 500;
  }

  .footer {
    background: linear-gradient(135deg, var(--dark-blue), var(--deep-green));
    color: white;
    padding: 40px 0;
    text-align: center;
  }

  .footer-links {
    display: flex;
    justify-content: center;
    gap: 30px;
    margin-bottom: 20px;
  }

  .footer-link {
    color: white;
    text-decoration: none;
    transition: color 0.3s ease;
  }

  .footer-link:hover {
    color: var(--accent-orange);
  }

  @media (max-width: 768px) {
    .header h1 {
      font-size: 2.2rem;
    }
    
    .nav-container {
      flex-direction: column;
      gap: 15px;
    }
    
    .nav-links {
      flex-wrap: wrap;
      justify-content: center;
    }
    
    article {
      padding: 30px;
    }
    
    .image-grid {
      grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    }
  }

  @media (max-width: 480px) {
    .header h1 {
      font-size: 1.8rem;
    }
    
    article {
      padding: 20px;
    }
    
    article h2 {
      font-size: 1.6rem;
    }
    
    article h3 {
      font-size: 1.3rem;
    }
    
    .image-grid {
      grid-template-columns: 1fr;
    }
  }