:root {
    --primary-bg: #121212;
    --secondary-bg: #1E1E1E;
    --text-color: #E0E0E0;
    --highlight: #00FFFF;
    --accent-purple: #BB86FC;
    --accent-green: #03DAC6;
    --card-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
  }

  @font-face {
    font-family: 'Roboto';
    src: local('Roboto'), local('Roboto-Regular');
    font-display: swap;
  }

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

  body {
    background: radial-gradient(circle at 10% 20%, #1a1a1a, var(--primary-bg));
    color: var(--text-color);
    font-family: 'Roboto', 'Helvetica Neue', sans-serif;
    line-height: 1.7;
    padding: 0;
    overflow-x: hidden;
  }

  .header-notice {
    background: linear-gradient(90deg, var(--accent-purple), var(--highlight));
    color: var(--secondary-bg);
    text-align: center;
    padding: 12px;
    font-weight: bold;
    font-size: 16px;
    position: relative;
    z-index: 100;
  }

  .hero {
    min-height: 400px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: url('https://images.gptkong.com/demo/sample1.png') center/cover no-repeat;
    position: relative;
    margin-bottom: 60px;
  }

  .hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(18, 18, 18, 0.7);
  }

  .hero-content {
    position: relative;
    z-index: 2;
    text-align: center;
    padding: 40px;
    max-width: 800px;
  }

  .hero h1 {
    font-size: 3rem;
    margin-bottom: 20px;
    background: linear-gradient(90deg, var(--highlight), var(--accent-green));
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
    text-shadow: 0 2px 10px rgba(0, 255, 255, 0.3);
  }

  .hero p {
    font-size: 1.2rem;
    margin-bottom: 30px;
  }

  .nav-container {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: var(--secondary-bg);
    box-shadow: 0 2px 15px rgba(0, 0, 0, 0.5);
  }

  .navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 5%;
    max-width: 1400px;
    margin: 0 auto;
  }

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

  .nav-links a {
    color: var(--text-color);
    text-decoration: none;
    font-weight: 500;
    position: relative;
    transition: color 0.3s;
  }

  .nav-links a:hover {
    color: var(--highlight);
  }

  .nav-links a::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--highlight);
    transition: width 0.3s;
  }

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

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

  article {
    background: var(--secondary-bg);
    border-radius: 12px;
    padding: 40px;
    margin-bottom: 60px;
    box-shadow: var(--card-shadow);
  }

  article h2 {
    font-size: 2.2rem;
    margin-bottom: 30px;
    color: var(--highlight);
    position: relative;
    padding-bottom: 15px;
  }

  article h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100px;
    height: 3px;
    background: linear-gradient(90deg, var(--highlight), transparent);
  }

  article h3 {
    font-size: 1.8rem;
    margin: 40px 0 20px;
    color: var(--accent-purple);
  }

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

  .highlight {
    color: var(--highlight);
    font-weight: 500;
  }

  .accent-purple {
    color: var(--accent-purple);
  }

  .accent-green {
    color: var(--accent-green);
  }

  pre {
    background: #2d2d2d;
    border-radius: 8px;
    padding: 20px;
    margin: 25px 0;
    overflow: auto;
    box-shadow: inset 0 0 10px rgba(0, 0, 0, 0.5);
    border-left: 4px solid var(--highlight);
  }

  code {
    font-family: 'Courier New', monospace;
    color: #f8f8f2;
  }

  .code-block {
    position: relative;
  }

  .code-block::before {
    content: 'CSS';
    position: absolute;
    top: 0;
    left: 0;
    background: var(--highlight);
    color: var(--secondary-bg);
    padding: 3px 10px;
    font-size: 0.8rem;
    border-radius: 0 0 5px 0;
  }

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

  .gallery-item {
    border-radius: 10px;
    overflow: hidden;
    box-shadow: var(--card-shadow);
    transition: transform 0.3s, box-shadow 0.3s;
  }

  .gallery-item:hover {
    transform: translateY(-10px);
    box-shadow: 0 15px 30px rgba(0, 0, 0, 0.4);
  }

  .gallery-item img {
    width: 100%;
    height: auto;
    display: block;
    transition: transform 0.5s;
  }

  .gallery-item:hover img {
    transform: scale(1.05);
  }

  .summary-card {
    background: linear-gradient(135deg, #252525, #1a1a1a);
    border-radius: 12px;
    padding: 30px;
    margin: 50px 0;
    box-shadow: var(--card-shadow);
    border-left: 5px solid var(--accent-purple);
  }

  .summary-card h4 {
    color: var(--highlight);
    margin-bottom: 20px;
    font-size: 1.5rem;
  }

  .summary-card ul {
    padding-left: 20px;
  }

  .summary-card li {
    margin-bottom: 10px;
    position: relative;
  }

  .summary-card li::before {
    content: '→';
    color: var(--accent-green);
    position: absolute;
    left: -20px;
  }

  footer {
    background: var(--secondary-bg);
    padding: 40px 0;
    text-align: center;
    margin-top: 80px;
    border-top: 1px solid #333;
  }

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

  .footer-links a {
    color: var(--text-color);
    text-decoration: none;
    transition: color 0.3s;
  }

  .footer-links a:hover {
    color: var(--highlight);
  }

  .copyright {
    color: #888;
    font-size: 0.9rem;
  }

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

    .nav-links {
      gap: 15px;
    }

    article {
      padding: 30px 20px;
    }

    article h2 {
      font-size: 1.8rem;
    }

    article h3 {
      font-size: 1.5rem;
    }

    .gallery {
      grid-template-columns: 1fr;
    }
  }

  @media (max-width: 480px) {
    .navbar {
      flex-direction: column;
      gap: 15px;
    }

    .nav-links {
      flex-wrap: wrap;
      justify-content: center;
    }

    .hero h1 {
      font-size: 1.8rem;
    }
  }

  /* 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: 0.7; }
  }

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

  /* Utility classes */
  .text-center {
    text-align: center;
  }

  .mb-30 {
    margin-bottom: 30px;
  }

  .mt-40 {
    margin-top: 40px;
  }