:root {
    --primary-color: #002B5B;
    --secondary-color: #00BFA6;
    --accent-color: #FF9800;
    --background-color: #F5F5F5;
    --text-color: #333333;
    --light-gray: #EAEAEA;
    --white: #FFFFFF;
    --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 {
    font-family: 'Open Sans', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background: var(--background-color);
    overflow-x: hidden;
  }

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

  .hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: var(--white);
    padding: 80px 0;
    text-align: center;
    position: relative;
    overflow: hidden;
    margin-bottom: 60px;
  }

  .hero::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: url('https://images.gptkong.com/demo/sample1.png') no-repeat;
    background-size: cover;
    opacity: 0.1;
    z-index: 0;
  }

  .hero-content {
    position: relative;
    z-index: 1;
  }

  .hero h1 {
    font-size: 2.8rem;
    margin-bottom: 20px;
    text-shadow: 0 2px 4px rgba(0,0,0,0.2);
  }

  .hero p {
    font-size: 1.2rem;
    max-width: 700px;
    margin: 0 auto 30px;
  }

  .notice {
    background: var(--white);
    color: var(--primary-color);
    padding: 15px;
    border-radius: 8px;
    display: inline-block;
    box-shadow: var(--shadow);
    font-weight: bold;
    margin-top: 30px;
  }

  .nav {
    position: sticky;
    top: 0;
    background: var(--white);
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    z-index: 100;
    padding: 15px 0;
  }

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

  .nav-logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
    text-decoration: none;
  }

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

  .nav-link {
    color: var(--text-color);
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition);
    position: relative;
  }

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

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

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

  .main {
    display: grid;
    grid-template-columns: 250px 1fr;
    gap: 40px;
    margin-bottom: 60px;
  }

  .sidebar {
    background: var(--white);
    border-radius: 8px;
    box-shadow: var(--shadow);
    padding: 30px;
    height: fit-content;
    position: sticky;
    top: 90px;
  }

  .sidebar-title {
    font-size: 1.2rem;
    color: var(--primary-color);
    margin-bottom: 20px;
    padding-bottom: 10px;
    border-bottom: 2px solid var(--light-gray);
  }

  .sidebar-nav {
    display: flex;
    flex-direction: column;
    gap: 15px;
  }

  .sidebar-link {
    color: var(--text-color);
    text-decoration: none;
    transition: var(--transition);
    padding: 8px 0;
    border-bottom: 1px dashed var(--light-gray);
  }

  .sidebar-link:hover {
    color: var(--secondary-color);
    padding-left: 10px;
  }

  .content {
    background: var(--white);
    border-radius: 8px;
    box-shadow: var(--shadow);
    padding: 40px;
  }

  article h2 {
    color: var(--primary-color);
    font-size: 1.8rem;
    margin: 40px 0 20px;
    position: relative;
    padding-bottom: 10px;
  }

  article h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 60px;
    height: 3px;
    background: var(--secondary-color);
  }

  article h3 {
    color: var(--primary-color);
    font-size: 1.4rem;
    margin: 30px 0 15px;
  }

  article p {
    margin-bottom: 20px;
    font-size: 1.05rem;
  }

  pre {
    background: #2d2d2d;
    color: #f8f8f2;
    padding: 20px;
    border-radius: 8px;
    overflow-x: auto;
    margin: 25px 0;
    font-size: 0.9rem;
    line-height: 1.5;
    box-shadow: var(--shadow);
  }

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

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

  .gallery-image {
    border-radius: 8px;
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: var(--transition);
    height: 300px;
  }

  .gallery-image:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0,0,0,0.15);
  }

  .gallery-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: var(--transition);
  }

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

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

  .footer-content {
    max-width: 800px;
    margin: 0 auto;
  }

  .footer-links {
    display: flex;
    justify-content: center;
    gap: 30px;
    margin: 30px 0;
  }

  .footer-link {
    color: var(--white);
    text-decoration: none;
    transition: var(--transition);
  }

  .footer-link:hover {
    color: var(--secondary-color);
  }

  .footer-copyright {
    margin-top: 30px;
    font-size: 0.9rem;
    opacity: 0.8;
  }

  @media (max-width: 992px) {
    .main {
      grid-template-columns: 1fr;
    }
    
    .sidebar {
      position: static;
    }
  }

  @media (max-width: 768px) {
    .hero h1 {
      font-size: 2.2rem;
    }
    
    .nav-container {
      flex-direction: column;
      gap: 15px;
    }
    
    .nav-links {
      gap: 15px;
    }
    
    .image-gallery {
      grid-template-columns: 1fr;
    }
  }

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

  .fade-in {
    animation: fadeIn 0.6s ease-out forwards;
  }

  .delay-1 { animation-delay: 0.2s; }
  .delay-2 { animation-delay: 0.4s; }
  .delay-3 { animation-delay: 0.6s; }