:root {
    --primary-color: #003366;
    --secondary-color: #00ccff;
    --accent-color: #ff6600;
    --highlight-color: #66ff66;
    --bg-gradient: linear-gradient(135deg, #f0f0f0 0%, #d9d9d9 100%);
    --card-shadow: 0 10px 30px rgba(0, 51, 102, 0.15);
    --text-light: #ffffff;
    --text-dark: #333333;
    --transition-base: all 0.4s cubic-bezier(0.25, 0.8, 0.25, 1);
  }

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

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

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

  .header {
    position: relative;
    height: 80vh;
    min-height: 600px;
    display: flex;
    align-items: center;
    background: radial-gradient(circle at 70% 30%, var(--primary-color) 0%, #001a33 100%);
    overflow: hidden;
    clip-path: polygon(0 0, 100% 0, 100% 90%, 0 100%);
    margin-bottom: 80px;
  }

  .header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: url('https://images.gptkong.com/demo/sample1.png') no-repeat center/cover;
    opacity: 0.15;
  }

  .header-content {
    position: relative;
    z-index: 2;
    width: 100%;
    color: var(--text-light);
    padding: 0 5%;
  }

  .header-title {
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: 20px;
    text-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
    animation: fadeInUp 1s ease-out;
  }

  .header-subtitle {
    font-size: 1.5rem;
    max-width: 700px;
    margin-bottom: 40px;
    opacity: 0.9;
    animation: fadeInUp 1s ease-out 0.3s forwards;
    opacity: 0;
  }

  .tech-badge {
    display: inline-block;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    padding: 15px 30px;
    border-radius: 50px;
    font-size: 1rem;
    margin-top: 30px;
    animation: fadeIn 1s ease-out 0.6s forwards;
    opacity: 0;
  }

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

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

  .nav {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background: rgba(0, 51, 102, 0.9);
    backdrop-filter: blur(10px);
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 5%;
    z-index: 1000;
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.1);
    transition: var(--transition-base);
  }

  .nav-scrolled {
    padding: 15px 5%;
    background: rgba(0, 51, 102, 0.95);
  }

  .nav-logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-light);
    text-decoration: none;
  }

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

  .nav-item {
    margin-left: 30px;
  }

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

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

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

  .section {
    padding: 100px 0;
    position: relative;
  }

  .section-title {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 50px;
    text-align: center;
    position: relative;
  }

  .section-title::after {
    content: '';
    position: absolute;
    bottom: -15px;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 4px;
    background: var(--accent-color);
    border-radius: 2px;
  }

  .grid-layout {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 50px;
  }

  .card {
    background: white;
    border-radius: 15px;
    overflow: hidden;
    box-shadow: var(--card-shadow);
    transition: var(--transition-base);
  }

  .card:hover {
    transform: translateY(-10px);
    box-shadow: 0 15px 40px rgba(0, 51, 102, 0.2);
  }

  .card-img {
    width: 100%;
    height: 200px;
    object-fit: cover;
  }

  .card-content {
    padding: 25px;
  }

  .card-title {
    font-size: 1.4rem;
    color: var(--primary-color);
    margin-bottom: 15px;
  }

  .card-text {
    color: #666;
    margin-bottom: 20px;
  }

  .btn {
    display: inline-block;
    background: var(--accent-color);
    color: white;
    padding: 12px 25px;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition-base);
  }

  .btn:hover {
    background: var(--highlight-color);
    transform: translateY(-3px);
    box-shadow: 0 5px 15px rgba(255, 102, 0, 0.3);
  }

  .feature-box {
    display: flex;
    align-items: center;
    margin-bottom: 40px;
  }

  .feature-icon {
    flex: 0 0 80px;
    height: 80px;
    background: var(--secondary-color);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-right: 30px;
    box-shadow: 0 5px 15px rgba(0, 204, 255, 0.3);
  }

  .feature-content {
    flex: 1;
  }

  .feature-title {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 10px;
  }

  .code-block {
    background: #2d2d2d;
    border-radius: 10px;
    padding: 20px;
    margin: 30px 0;
    overflow-x: auto;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
  }

  .code-block pre {
    margin: 0;
    font-family: 'Courier New', monospace;
    color: #f8f8f2;
    line-height: 1.5;
    tab-size: 2;
  }

  .code-block code {
    display: block;
    white-space: pre;
  }

  .illustration-container {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 20px;
    margin: 50px 0;
  }

  .illustration {
    width: 150px;
    height: 150px;
    border-radius: 20px;
    object-fit: cover;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    transition: var(--transition-base);
  }

  .illustration:hover {
    transform: scale(1.1) rotate(5deg);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.2);
  }

  .faq-container {
    max-width: 800px;
    margin: 0 auto;
  }

  .faq-item {
    margin-bottom: 15px;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.05);
  }

  .faq-title {
    background: white;
    padding: 20px;
    cursor: pointer;
    font-weight: 600;
    color: var(--primary-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: var(--transition-base);
  }

  .faq-title:hover {
    background: #f5f5f5;
  }

  .faq-title::after {
    content: '+';
    font-size: 1.5rem;
  }

  .faq-item.active .faq-title::after {
    content: '-';
  }

  .faq-content {
    max-height: 0;
    overflow: hidden;
    background: #f9f9f9;
    transition: max-height 0.5s ease;
  }

  .faq-item.active .faq-content {
    max-height: 500px;
  }

  .faq-inner {
    padding: 20px;
  }

  .back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: var(--accent-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    opacity: 0;
    transform: translateY(20px);
    transition: var(--transition-base);
    box-shadow: 0 5px 15px rgba(255, 102, 0, 0.3);
    z-index: 999;
  }

  .back-to-top.show {
    opacity: 1;
    transform: translateY(0);
  }

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

  .footer-text {
    opacity: 0.8;
    margin-top: 20px;
  }

  @media (max-width: 768px) {
    .header-title {
      font-size: 2.5rem;
    }
    
    .header-subtitle {
      font-size: 1.2rem;
    }
    
    .nav-menu {
      display: none;
    }
    
    .grid-layout {
      grid-template-columns: 1fr;
    }
    
    .feature-box {
      flex-direction: column;
      text-align: center;
    }
    
    .feature-icon {
      margin-right: 0;
      margin-bottom: 20px;
    }
  }