:root {
    --primary: #FF6F61;
    --secondary: #333333;
    --accent: #4A90E2;
    --bg-light: #FFFFFF;
    --bg-dark: #1A1A1A;
    --text-primary: #333333;
    --text-secondary: #666666;
    --success: #5CB85C;
    --warning: #F0AD4E;
    --danger: #D9534F;
    --radius: 12px;
    --shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
    --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', system-ui, -apple-system, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background: linear-gradient(135deg, #F8F9FA 0%, #E9ECEF 100%);
    min-height: 100%;
    padding-bottom: 60px;
  }

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

  /* Header Styles */
  .header {
    background: linear-gradient(90deg, var(--primary) 0%, var(--secondary) 100%);
    color: var(--bg-light);
    padding: 30px 0;
    text-align: center;
    margin-bottom: 40px;
    position: relative;
    overflow: hidden;
  }

  .header::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: url('https://images.gptkong.com/demo/sample3.png') center/cover no-repeat;
    opacity: 0.15;
    z-index: 0;
  }

  .header-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
    margin: 0 auto;
  }

  .header h1 {
    font-size: 2.5rem;
    margin-bottom: 15px;
    font-weight: 700;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
  }

  .header p {
    font-size: 1.1rem;
    opacity: 0.9;
    margin-bottom: 20px;
  }

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

  /* Navigation */
  .navbar {
    position: sticky;
    top: 0;
    background-color: var(--bg-light);
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    z-index: 1000;
    padding: 15px 0;
  }

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

  .nav-logo {
    font-weight: 700;
    color: var(--primary);
    font-size: 1.2rem;
    text-decoration: none;
  }

  .nav-menu {
    display: flex;
    list-style: none;
  }

  .nav-item {
    margin-left: 25px;
  }

  .nav-link {
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 600;
    position: relative;
    transition: var(--transition);
    padding: 5px 0;
  }

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

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

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

  /* Main Content */
  .main {
    display: grid;
    grid-template-columns: 250px 1fr;
    gap: 30px;
    margin-top: 30px;
  }

  @media (max-width: 768px) {
    .main {
      grid-template-columns: 1fr;
    }
  }

  /* Sidebar */
  .sidebar {
    position: sticky;
    top: 80px;
    height: fit-content;
    background-color: var(--bg-light);
    border-radius: var(--radius);
    padding: 20px;
    box-shadow: var(--shadow);
  }

  .sidebar-title {
    font-size: 1.1rem;
    color: var(--primary);
    margin-bottom: 15px;
    padding-bottom: 10px;
    border-bottom: 1px solid rgba(0, 0, 0, 0.1);
  }

  .sidebar-menu {
    list-style: none;
  }

  .sidebar-item {
    margin-bottom: 10px;
  }

  .sidebar-link {
    color: var(--text-primary);
    text-decoration: none;
    transition: var(--transition);
    display: block;
    padding: 8px 0;
  }

  .sidebar-link:hover {
    color: var(--primary);
    transform: translateX(5px);
  }

  /* Article */
  .article {
    background-color: var(--bg-light);
    border-radius: var(--radius);
    padding: 30px;
    box-shadow: var(--shadow);
  }

  .article h2 {
    color: var(--primary);
    margin: 30px 0 20px;
    font-size: 1.8rem;
    position: relative;
    padding-bottom: 10px;
  }

  .article h2::after {
    content: "";
    position: absolute;
    bottom: 0;
    left: 0;
    width: 60px;
    height: 3px;
    background: linear-gradient(90deg, var(--primary) 0%, var(--accent) 100%);
    border-radius: 3px;
  }

  .article h3 {
    color: var(--secondary);
    margin: 25px 0 15px;
    font-size: 1.4rem;
  }

  .article p {
    margin-bottom: 20px;
    color: var(--text-primary);
    font-size: 1.05rem;
    line-height: 1.7;
  }

  /* Code Blocks */
  pre {
    background-color: var(--bg-dark);
    border-radius: var(--radius);
    padding: 20px;
    margin: 20px 0;
    overflow-x: auto;
    position: relative;
  }

  pre::before {
    content: "CSS";
    position: absolute;
    top: 0;
    left: 0;
    background-color: var(--primary);
    color: white;
    padding: 3px 10px;
    border-radius: var(--radius) 0 var(--radius) 0;
    font-size: 0.8rem;
    font-weight: bold;
  }

  code {
    font-family: 'Fira Code', monospace;
    color: #E0E0E0;
    font-size: 0.9rem;
  }

  /* Cards */
  .card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 20px;
    margin: 30px 0;
  }

  .card {
    background-color: var(--bg-light);
    border-radius: var(--radius);
    padding: 20px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
    transition: var(--transition);
    border: 1px solid rgba(0, 0, 0, 0.05);
  }

  .card:hover {
    transform: translateY(-5px);
    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.15);
  }

  .card-img {
    width: 100%;
    height: 180px;
    object-fit: cover;
    border-radius: calc(var(--radius) - 5px);
    margin-bottom: 15px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
  }

  /* Images */
  .image-container {
    display: flex;
    flex-wrap: wrap;
    gap: 15px;
    margin: 30px 0;
    justify-content: center;
  }

  .image-box {
    width: 150px;
    height: 150px;
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    transition: var(--transition);
  }

  .image-box:hover {
    transform: scale(1.05);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
  }

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

  .image-box:hover img {
    transform: scale(1.1);
  }

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

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

  /* Responsive Adjustments */
  @media (max-width: 992px) {
    .header h1 {
      font-size: 2rem;
    }
  }

  @media (max-width: 768px) {
    .nav-menu {
      display: none;
    }
    
    .header {
      padding: 20px 0;
    }
    
    .article {
      padding: 20px;
    }
  }

  @media (max-width: 576px) {
    .header h1 {
      font-size: 1.8rem;
    }
    
    .header p {
      font-size: 1rem;
    }
    
    .card-grid {
      grid-template-columns: 1fr;
    }
  }