:root {
    --primary-color: #1E3A8A;
    --secondary-color: #3B82F6;
    --accent-color: #F59E0B;
    --light-bg: #F3F4F6;
    --dark-text: #111827;
    --light-text: #ffffff;
    --card-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    --transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
  }

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

  body {
    font-family: 'Open Sans', sans-serif;
    line-height: 1.7;
    color: var(--dark-text);
    background: var(--light-bg);
    overflow-x: hidden;
  }

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

  h1, h2, h3, h4 {
    font-family: 'Roboto', sans-serif;
    margin-bottom: 1.5rem;
    color: var(--primary-color);
    line-height: 1.3;
  }

  h2 { font-size: 2.2rem; }
  h3 { font-size: 1.8rem; }
  p { font-size: 1.1rem; margin-bottom: 1.5rem; }

  /* Hero Section */
  .hero {
    min-height: 600px;
    display: flex;
    align-items: center;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: var(--light-text);
    position: relative;
    overflow: hidden;
    padding: 100px 0;
  }

  .hero::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: 0.15;
    z-index: 1;
  }

  .hero-content {
    position: relative;
    z-index: 2;
    max-width: 800px;
    margin: 0 auto;
    text-align: center;
    padding: 0 20px;
  }

  .hero h1 {
    font-size: 3.5rem;
    margin-bottom: 1.5rem;
    animation: fadeInUp 1s ease-out;
  }

  .hero p {
    font-size: 1.3rem;
    margin-bottom: 2.5rem;
    opacity: 0;
    animation: fadeIn 1s ease-out 0.5s forwards;
  }

  .hero-btn {
    display: inline-block;
    background: var(--accent-color);
    color: var(--light-text);
    padding: 15px 30px;
    border-radius: 50px;
    text-decoration: none;
    font-weight: bold;
    font-size: 1.1rem;
    transition: var(--transition);
    opacity: 0;
    animation: fadeIn 1s ease-out 1s forwards;
    box-shadow: 0 5px 15px rgba(245, 158, 11, 0.3);
  }

  .hero-btn:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(245, 158, 11, 0.4);
  }

  /* Main Content */
  .main-content {
    padding: 80px 0;
    background: var(--light-bg);
  }

  .section {
    margin-bottom: 80px;
    background: white;
    border-radius: 15px;
    padding: 50px;
    box-shadow: var(--card-shadow);
    position: relative;
    overflow: hidden;
  }

  .section::after {
    content: '';
    position: absolute;
    bottom: 0;
    right: 0;
    width: 200px;
    height: 200px;
    background: url('https://images.gptkong.com/demo/sample2.png') center/contain no-repeat;
    opacity: 0.1;
    z-index: 0;
  }

  .section-title {
    position: relative;
    display: inline-block;
    margin-bottom: 2.5rem;
    z-index: 1;
  }

  .section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 0;
    width: 60px;
    height: 4px;
    background: var(--accent-color);
    border-radius: 2px;
  }

  /* Code Blocks */
  pre {
    background: #1E1E1E;
    color: #D4D4D4;
    padding: 20px;
    border-radius: 8px;
    overflow-x: auto;
    margin: 2rem 0;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
    position: relative;
  }

  pre::before {
    content: 'CSS';
    position: absolute;
    top: 0;
    left: 0;
    background: var(--accent-color);
    color: white;
    padding: 5px 15px;
    border-radius: 0 0 5px 0;
    font-size: 0.8rem;
    font-weight: bold;
  }

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

  /* Image Gallery */
  .image-gallery {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
    margin: 2rem 0;
  }

  .gallery-item {
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    transition: var(--transition);
    position: relative;
  }

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

  .gallery-item img {
    width: 100%;
    height: 250px;
    object-fit: cover;
    display: block;
    transition: transform 0.5s ease;
  }

  .gallery-item:hover img {
    transform: scale(1.1);
  }

  /* Navigation */
  .navbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background: rgba(30, 58, 138, 0.95);
    padding: 20px 0;
    z-index: 1000;
    backdrop-filter: blur(10px);
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    transition: all 0.3s ease;
  }

  .nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
  }

  .nav-logo {
    color: white;
    font-size: 1.5rem;
    font-weight: bold;
    text-decoration: none;
  }

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

  .nav-link {
    color: white;
    text-decoration: none;
    font-weight: 500;
    position: relative;
    transition: color 0.3s ease;
  }

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

  .nav-link::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--accent-color);
    transition: width 0.3s ease;
  }

  .nav-link:hover::after {
    width: 100%;
  }

  /* Back to Top */
  .back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: var(--secondary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    box-shadow: 0 5px 15px rgba(59, 130, 246, 0.3);
    z-index: 999;
  }

  .back-to-top.active {
    opacity: 1;
    visibility: visible;
  }

  .back-to-top:hover {
    background: var(--accent-color);
    transform: translateY(-5px);
  }

  /* Footer */
  .footer {
    background: var(--primary-color);
    color: white;
    padding: 50px 0;
    text-align: center;
  }

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

  /* Animations */
  @keyframes fadeInUp {
    from {
      opacity: 0;
      transform: translateY(30px);
    }
    to {
      opacity: 1;
      transform: translateY(0);
    }
  }

  @keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
  }

  /* Responsive */
  @media (max-width: 992px) {
    .hero h1 {
      font-size: 2.8rem;
    }
    .section {
      padding: 40px;
    }
  }

  @media (max-width: 768px) {
    .hero {
      min-height: 500px;
      padding: 80px 0;
    }
    .hero h1 {
      font-size: 2.2rem;
    }
    .hero p {
      font-size: 1.1rem;
    }
    .section {
      padding: 30px;
    }
    .nav-links {
      gap: 20px;
    }
  }

  @media (max-width: 576px) {
    .hero h1 {
      font-size: 1.8rem;
    }
    .hero-btn {
      padding: 12px 25px;
    }
    .section {
      padding: 25px;
    }
    .nav-links {
      gap: 15px;
    }
  }

  /* Utility Classes */
  .text-center { text-align: center; }
  .mb-0 { margin-bottom: 0 !important; }
  .mt-5 { margin-top: 3rem; }
  .pb-5 { padding-bottom: 3rem; }
  .note {
    background: rgba(59, 130, 246, 0.1);
    border-left: 4px solid var(--secondary-color);
    padding: 15px;
    margin: 2rem 0;
    border-radius: 0 5px 5px 0;
  }

  /* Style Reference Note */
  .style-reference {
    position: fixed;
    bottom: 20px;
    left: 20px;
    background: var(--accent-color);
    color: white;
    padding: 10px 15px;
    border-radius: 5px;
    font-size: 0.9rem;
    z-index: 1000;
    box-shadow: 0 3px 10px rgba(245, 158, 11, 0.3);
  }