:root {
    --primary-dark: #0d47a1;
    --primary-light: #42a5f5;
    --accent-orange: #ff9800;
    --accent-green: #4caf50;
    --neutral-light: #f5f5f5;
    --neutral-dark: #333;
    --text-primary: #212121;
    --text-secondary: #757575;
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 8px rgba(0,0,0,0.15);
    --shadow-lg: 0 8px 16px rgba(0,0,0,0.2);
    --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', 'Open Sans', sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    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 Styles */
  .header {
    background: linear-gradient(to right, var(--primary-dark), var(--primary-light));
    color: white;
    padding: 1.5rem 0;
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-md);
  }

  .header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
  }

  .logo {
    font-size: 1.8rem;
    font-weight: 700;
    letter-spacing: 1px;
    text-shadow: 0 2px 4px rgba(0,0,0,0.2);
  }

  .tagline {
    font-size: 0.9rem;
    opacity: 0.9;
    margin-top: 0.5rem;
  }

  /* Navigation */
  .nav {
    display: flex;
    gap: 2rem;
  }

  .nav-link {
    color: white;
    text-decoration: none;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    transition: var(--transition);
  }

  .nav-link:hover {
    background: rgba(255,255,255,0.2);
  }

  /* Hero Section */
  .hero {
    padding: 8rem 0 4rem;
    background: url('https://images.gptkong.com/demo/sample1.png') no-repeat right center/contain;
    min-height: 500px;
  }

  .hero-content {
    max-width: 600px;
    background: rgba(255,255,255,0.9);
    padding: 2rem;
    border-radius: 8px;
    box-shadow: var(--shadow-lg);
  }

  .hero-title {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--primary-dark);
  }

  .hero-subtitle {
    font-size: 1.2rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
  }

  /* Main Content */
  .main {
    padding: 4rem 0;
  }

  article {
    background: white;
    border-radius: 8px;
    padding: 3rem;
    box-shadow: var(--shadow-sm);
    margin-bottom: 3rem;
  }

  h2 {
    font-size: 1.8rem;
    color: var(--primary-dark);
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--neutral-light);
  }

  h3 {
    font-size: 1.5rem;
    color: var(--primary-light);
    margin: 2rem 0 1rem;
  }

  p {
    margin-bottom: 1.5rem;
    font-size: 1.1rem;
    line-height: 1.8;
  }

  /* Code Blocks */
  pre {
    background: #f8f8f8;
    border-radius: 6px;
    padding: 1.5rem;
    margin: 1.5rem 0;
    overflow: auto;
    border-left: 4px solid var(--primary-light);
  }

  code {
    font-family: 'Courier New', monospace;
    font-size: 0.9rem;
    color: #333;
  }

  /* Images */
  .img-container {
    display: flex;
    flex-wrap: wrap;
    gap: 1.5rem;
    margin: 2rem 0;
  }

  .img-card {
    flex: 1 1 300px;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
  }

  .img-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
  }

  .img-card img {
    width: 100%;
    height: auto;
    display: block;
  }

  /* Table Styles */
  table {
    width: 100%;
    border-collapse: collapse;
    margin: 2rem 0;
    box-shadow: var(--shadow-sm);
  }

  th, td {
    padding: 1rem;
    text-align: left;
    border-bottom: 1px solid var(--neutral-light);
  }

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

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

  /* Footer */
  .footer {
    background: var(--neutral-dark);
    color: white;
    padding: 3rem 0;
    text-align: center;
  }

  .footer p {
    margin-bottom: 0;
    opacity: 0.8;
  }

  /* Responsive Adjustments */
  @media (max-width: 768px) {
    .header-content {
      flex-direction: column;
      text-align: center;
    }

    .nav {
      margin-top: 1rem;
      flex-wrap: wrap;
      justify-content: center;
    }

    .hero {
      background-position: center;
      padding: 6rem 0 2rem;
    }

    .hero-content {
      max-width: 100%;
    }

    article {
      padding: 2rem;
    }
  }

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

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

  /* Utility Classes */
  .btn {
    display: inline-block;
    padding: 0.8rem 1.5rem;
    border-radius: 4px;
    font-weight: 500;
    text-decoration: none;
    transition: var(--transition);
    margin-right: 1rem;
    margin-bottom: 1rem;
  }

  .btn-primary {
    background: var(--accent-orange);
    color: white;
  }

  .btn-primary:hover {
    background: #fb8c00;
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
  }

  .btn-secondary {
    background: var(--primary-light);
    color: white;
  }

  .btn-secondary:hover {
    background: #1e88e5;
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
  }

  .text-center {
    text-align: center;
  }

  .mt-1 { margin-top: 1rem; }
  .mt-2 { margin-top: 2rem; }
  .mt-3 { margin-top: 3rem; }
  .mb-1 { margin-bottom: 1rem; }
  .mb-2 { margin-bottom: 2rem; }
  .mb-3 { margin-bottom: 3rem; }

  /* Reference Notice */
  .reference-notice {
    background: var(--neutral-light);
    padding: 1rem;
    border-radius: 4px;
    margin: 2rem 0;
    text-align: center;
    font-size: 0.9rem;
    color: var(--text-secondary);
  }