:root {
    --primary: #1e3c72;
    --secondary: #2a5298;
    --accent: #ffa500;
    --light: #f8f9fa;
    --dark: #212529;
    --gradient: linear-gradient(135deg, var(--primary), var(--secondary));
    --shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
  }

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

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

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

  header {
    background: var(--gradient);
    color: white;
    padding: 60px 0;
    text-align: center;
    position: relative;
    overflow: hidden;
  }

  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 h1 {
    font-size: 3rem;
    margin-bottom: 20px;
    position: relative;
    text-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
  }

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

  .reference {
    background: rgba(255, 255, 255, 0.2);
    padding: 10px 20px;
    border-radius: 30px;
    display: inline-block;
    font-size: 0.9rem;
    backdrop-filter: blur(5px);
    margin-top: 20px;
  }

  nav {
    position: sticky;
    top: 0;
    background: rgba(30, 60, 114, 0.95);
    backdrop-filter: blur(10px);
    z-index: 1000;
    box-shadow: var(--shadow);
  }

  nav ul {
    display: flex;
    justify-content: center;
    list-style: none;
    padding: 15px 0;
  }

  nav li {
    margin: 0 15px;
  }

  nav a {
    color: white;
    text-decoration: none;
    font-weight: 500;
    padding: 5px 10px;
    border-radius: 4px;
    transition: var(--transition);
  }

  nav a:hover {
    background: rgba(255, 255, 255, 0.2);
    color: var(--accent);
  }

  article {
    padding: 60px 0;
  }

  article h2 {
    font-size: 2.2rem;
    color: var(--primary);
    margin-bottom: 30px;
    text-align: center;
    position: relative;
  }

  article h2::after {
    content: "";
    display: block;
    width: 100px;
    height: 4px;
    background: var(--accent);
    margin: 15px auto;
    border-radius: 2px;
  }

  article h3 {
    font-size: 1.8rem;
    color: var(--secondary);
    margin: 40px 0 20px;
    position: relative;
    padding-left: 20px;
  }

  article h3::before {
    content: "";
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 8px;
    height: 8px;
    background: var(--accent);
    border-radius: 50%;
  }

  article p {
    font-size: 1.1rem;
    margin-bottom: 20px;
    line-height: 1.8;
  }

  .content-block {
    background: white;
    border-radius: 10px;
    padding: 40px;
    margin: 40px 0;
    box-shadow: var(--shadow);
    transition: var(--transition);
  }

  .content-block:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.15);
  }

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

  .image-card {
    border-radius: 10px;
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: var(--transition);
    position: relative;
  }

  .image-card:hover {
    transform: scale(1.03);
  }

  .image-card img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
  }

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

  .image-card:hover::after {
    opacity: 1;
  }

  pre {
    background: #f5f7fa;
    border-radius: 8px;
    padding: 20px;
    margin: 30px 0;
    overflow: auto;
    font-family: 'Courier New', monospace;
    font-size: 0.95rem;
    line-height: 1.5;
    border-left: 4px solid var(--accent);
  }

  code {
    font-family: 'Courier New', monospace;
    background: rgba(255, 165, 0, 0.1);
    padding: 2px 6px;
    border-radius: 4px;
    color: #d63384;
  }

  .btn {
    display: inline-block;
    background: var(--accent);
    color: white;
    padding: 12px 25px;
    border-radius: 30px;
    text-decoration: none;
    font-weight: 500;
    margin: 20px 0;
    transition: var(--transition);
    box-shadow: 0 4px 15px rgba(255, 165, 0, 0.3);
  }

  .btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(255, 165, 0, 0.4);
  }

  footer {
    background: var(--gradient);
    color: white;
    text-align: center;
    padding: 40px 0;
    margin-top: 60px;
  }

  @media (max-width: 768px) {
    header h1 {
      font-size: 2.2rem;
    }

    nav ul {
      flex-wrap: wrap;
    }

    nav li {
      margin: 5px 10px;
    }

    .content-block {
      padding: 30px;
    }

    article h2 {
      font-size: 1.8rem;
    }

    article h3 {
      font-size: 1.5rem;
    }
  }

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

  .fade-in {
    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; }