:root {
  --primary: #0D2C54;
  --secondary: #AAB8C2;
  --accent: #3F51B5;
  --highlight: #FFC107;
  --bg: #F7F9FB;
  --text: #333;
  --light: #ECEFF1;
  --card-bg: rgba(247, 249, 251, 0.7);
  --border: rgba(170, 184, 194, 0.3);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Roboto', sans-serif;
}

body {
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  padding-top: 80px;
}

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

.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  background: rgba(13, 44, 84, 0.9);
  backdrop-filter: blur(10px);
  z-index: 1000;
  padding: 15px 0;
  box-shadow: 0 2px 15px rgba(0, 0, 0, 0.1);
}

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

.logo {
  color: white;
  font-size: 1.5rem;
  font-weight: 700;
  text-decoration: none;
}

.nav-links {
  display: flex;
  gap: 25px;
}

.nav-links a {
  color: white;
  text-decoration: none;
  font-weight: 500;
  transition: color 0.3s ease;
}

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

.hero {
  background: linear-gradient(135deg, rgba(13, 44, 84, 0.8), rgba(63, 81, 181, 0.6));
  padding: 80px 0;
  margin-bottom: 60px;
  position: relative;
  overflow: hidden;
}

.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: 0.1;
  z-index: -1;
}

.hero-content {
  max-width: 800px;
  margin: 0 auto;
  text-align: center;
  color: white;
}

.hero h1 {
  font-size: 2.5rem;
  margin-bottom: 20px;
  text-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
}

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

.notice {
  background: rgba(255, 255, 255, 0.2);
  backdrop-filter: blur(5px);
  padding: 15px;
  border-radius: 8px;
  margin: 30px 0;
  text-align: center;
  border: 1px solid rgba(255, 255, 255, 0.3);
}

.main {
  display: grid;
  grid-template-columns: 250px 1fr;
  gap: 30px;
  margin-bottom: 60px;
}

.sidebar {
  background: var(--card-bg);
  backdrop-filter: blur(8px);
  border-radius: 12px;
  padding: 20px;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.05);
  height: fit-content;
  position: sticky;
  top: 100px;
}

.sidebar h3 {
  color: var(--primary);
  margin-bottom: 20px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border);
}

.sidebar-links {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.sidebar-links a {
  color: var(--text);
  text-decoration: none;
  padding: 8px 12px;
  border-radius: 6px;
  transition: all 0.3s ease;
}

.sidebar-links a:hover {
  background: rgba(63, 81, 181, 0.1);
  color: var(--accent);
}

.content {
  background: var(--card-bg);
  backdrop-filter: blur(5px);
  border-radius: 12px;
  padding: 30px;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.05);
}

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

article h2::after {
  content: '';
  position: absolute;
  bottom: -8px;
  left: 0;
  width: 60px;
  height: 3px;
  background: linear-gradient(90deg, var(--accent), var(--highlight));
  border-radius: 3px;
}

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

article p {
  margin-bottom: 15px;
  font-size: 1.1rem;
}

pre {
  background: rgba(13, 44, 84, 0.05);
  border-radius: 8px;
  padding: 15px;
  margin: 20px 0;
  overflow-x: auto;
  border: 1px solid var(--border);
}

code {
  font-family: 'Courier New', monospace;
  font-size: 0.9rem;
  color: var(--primary);
}

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

.card {
  background: var(--card-bg);
  backdrop-filter: blur(5px);
  border-radius: 12px;
  padding: 20px;
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.05);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.1);
}

.card img {
  width: 100%;
  border-radius: 8px;
  margin-bottom: 15px;
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
  transition: transform 0.3s ease;
}

.card:hover img {
  transform: scale(1.02);
}

.footer {
  background: var(--primary);
  color: white;
  padding: 40px 0;
  text-align: center;
}

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

.footer-links a {
  color: white;
  text-decoration: none;
  transition: color 0.3s ease;
}

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

@media (max-width: 768px) {
  .main {
    grid-template-columns: 1fr;
  }
  
  .sidebar {
    position: static;
    margin-bottom: 30px;
  }
  
  .hero h1 {
    font-size: 2rem;
  }
  
  .hero p {
    font-size: 1rem;
  }
}

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

.content {
  animation: fadeIn 0.6s ease forwards;
}

/* Button styles */
.btn {
  display: inline-block;
  background: linear-gradient(135deg, var(--accent), var(--highlight));
  color: white;
  padding: 12px 25px;
  border-radius: 25px;
  text-decoration: none;
  font-weight: 500;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  box-shadow: 0 4px 10px rgba(63, 81, 181, 0.3);
}

.btn:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 15px rgba(63, 81, 181, 0.4);
}