:root {
    --primary: #1A365D;
    --secondary: #BFC2C7;
    --accent: #FF8C00;
    --highlight: #34C759;
    --bg: #F5F5F5;
    --text: #333;
    --card-bg: #fff;
    --radius: 12px;
    --shadow: 0 4px 20px rgba(0,0,0,0.08);
    --transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
  }

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

  body {
    background: var(--bg);
    color: var(--text);
    font-family: 'Roboto', 'Helvetica', Arial, sans-serif;
    line-height: 1.6;
    padding: 0;
    margin: 0;
    overflow-x: hidden;
  }

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

  header {
    background: linear-gradient(135deg, var(--primary), #0F2A4A);
    color: white;
    padding: 2rem 0;
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow);
  }

  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;
    text-align: center;
    padding: 2rem;
  }

  h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    background: linear-gradient(90deg, white, var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-shadow: 0 2px 4px rgba(0,0,0,0.1);
  }

  .tagline {
    font-size: 1.2rem;
    opacity: 0.9;
    margin-bottom: 2rem;
  }

  .notice {
    background: rgba(255,255,255,0.2);
    padding: 1rem;
    border-radius: var(--radius);
    margin: 2rem auto;
    max-width: 600px;
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255,255,255,0.1);
  }

  article {
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin: 3rem 0;
    padding: 2.5rem;
    position: relative;
    overflow: hidden;
  }

  article::after {
    content: "";
    position: absolute;
    top: 0;
    right: 0;
    width: 200px;
    height: 200px;
    background: radial-gradient(circle, var(--highlight) 0%, transparent 70%);
    opacity: 0.1;
    z-index: 0;
  }

  h2 {
    color: var(--primary);
    font-size: 1.8rem;
    margin: 2rem 0 1.5rem;
    position: relative;
    padding-bottom: 0.5rem;
  }

  h2::after {
    content: "";
    position: absolute;
    bottom: 0;
    left: 0;
    width: 60px;
    height: 3px;
    background: linear-gradient(90deg, var(--accent), var(--highlight));
  }

  h3 {
    color: var(--primary);
    font-size: 1.4rem;
    margin: 1.5rem 0 1rem;
  }

  p {
    margin-bottom: 1.2rem;
    font-size: 1.05rem;
  }

  pre {
    background: #1E1E1E;
    color: #f8f8f2;
    padding: 1.5rem;
    border-radius: var(--radius);
    margin: 1.5rem 0;
    overflow: auto;
    font-family: 'Courier New', monospace;
    position: relative;
    box-shadow: inset 0 0 10px rgba(0,0,0,0.5);
  }

  pre::before {
    content: "CSS";
    position: absolute;
    top: 0;
    left: 0;
    background: var(--accent);
    color: white;
    padding: 0.2rem 0.8rem;
    border-radius: var(--radius) 0 var(--radius) 0;
    font-size: 0.8rem;
  }

  code {
    font-family: 'Courier New', monospace;
    background: rgba(0,0,0,0.05);
    padding: 0.2rem 0.4rem;
    border-radius: 4px;
    font-size: 0.9rem;
  }

  table {
    width: 100%;
    border-collapse: collapse;
    margin: 1.5rem 0;
    box-shadow: 0 0 20px rgba(0,0,0,0.1);
    border-radius: var(--radius);
    overflow: hidden;
  }

  th, td {
    padding: 1rem;
    text-align: left;
    border-bottom: 1px solid rgba(0,0,0,0.05);
  }

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

  tr:nth-child(even) {
    background: rgba(0,0,0,0.02);
  }

  tr:hover {
    background: rgba(0,0,0,0.05);
  }

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

  .gallery-item {
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: var(--transition);
    position: relative;
  }

  .gallery-item:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px 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);
  }

  .gallery-item::after {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(to top, rgba(0,0,0,0.5), transparent 50%);
    opacity: 0;
    transition: var(--transition);
  }

  .gallery-item:hover::after {
    opacity: 1;
  }

  .nav-links {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 1rem;
    margin: 2rem 0;
  }

  .nav-link {
    padding: 0.8rem 1.5rem;
    background: linear-gradient(135deg, var(--primary), var(--highlight));
    color: white;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
  }

  .nav-link:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 15px rgba(0,0,0,0.2);
    background: linear-gradient(135deg, var(--highlight), var(--accent));
  }

  footer {
    background: var(--primary);
    color: white;
    padding: 2rem 0;
    text-align: center;
    margin-top: 3rem;
  }

  @media (max-width: 768px) {
    h1 {
      font-size: 2rem;
    }
    
    article {
      padding: 1.5rem;
    }
    
    .gallery {
      grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    }
  }

  @media (max-width: 480px) {
    h1 {
      font-size: 1.8rem;
    }
    
    article {
      padding: 1.2rem;
    }
    
    pre {
      padding: 1rem;
      font-size: 0.9rem;
    }
    
    .nav-links {
      flex-direction: column;
      align-items: center;
    }
    
    .nav-link {
      width: 100%;
      text-align: center;
    }
  }

  /* Animations */
  @keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-10px); }
  }

  .floating {
    animation: float 3s ease-in-out infinite;
  }

  @keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.6; }
  }

  .pulse {
    animation: pulse 2s ease-in-out infinite;
  }