:root {
  --primary: #0B3D91;
  --secondary: #1E50A2;
  --accent: #34C759;
  --highlight: #FFA500;
  --light: #F5F5F5;
  --dark: #333333;
  --text: #FFFFFF;
  --text-dark: #333333;
}

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

body {
  font-family: 'Open Sans', sans-serif;
  line-height: 1.6;
  color: var(--text-dark);
  background: linear-gradient(135deg, #f5f7fa 0%, #e4e8f0 100%);
  min-height: 100%;
}

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

.header {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: var(--text);
  padding: 2rem 0;
  text-align: center;
  border-radius: 0 0 20px 20px;
  box-shadow: 0 10px 30px rgba(11, 61, 145, 0.2);
  margin-bottom: 3rem;
  position: relative;
  overflow: hidden;
}

.header::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;
}

.header h1 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
  position: relative;
  z-index: 1;
  text-shadow: 0 2px 4px rgba(0,0,0,0.3);
}

.header p {
  font-size: 1.2rem;
  max-width: 800px;
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.notice {
  background: var(--light);
  padding: 1rem;
  border-radius: 8px;
  margin: 2rem auto;
  text-align: center;
  box-shadow: 0 4px 6px rgba(0,0,0,0.1);
  max-width: 800px;
  border-left: 4px solid var(--accent);
}

.main-content {
  display: grid;
  grid-template-columns: 1fr;
  gap: 3rem;
  margin-bottom: 3rem;
}

.article-section {
  background: white;
  border-radius: 12px;
  padding: 2.5rem;
  box-shadow: 0 10px 30px rgba(0,0,0,0.08);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  position: relative;
  overflow: hidden;
}

.article-section:hover {
  transform: translateY(-5px);
  box-shadow: 0 15px 35px rgba(0,0,0,0.12);
}

.article-section h2 {
  color: var(--primary);
  margin-bottom: 1.5rem;
  font-size: 1.8rem;
  position: relative;
  padding-bottom: 0.5rem;
}

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

.article-section h3 {
  color: var(--secondary);
  margin: 1.5rem 0 1rem;
  font-size: 1.4rem;
}

.article-section p {
  margin-bottom: 1.5rem;
  font-size: 1.1rem;
}

.code-container {
  background: #282c34;
  border-radius: 8px;
  padding: 1.5rem;
  margin: 1.5rem 0;
  overflow-x: auto;
  box-shadow: inset 0 0 10px rgba(0,0,0,0.5);
}

pre {
  margin: 0;
  font-family: 'Courier New', monospace;
  color: #abb2bf;
  line-height: 1.5;
  tab-size: 2;
}

.image-gallery {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
  margin: 2rem 0;
}

.gallery-item {
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 5px 15px rgba(0,0,0,0.1);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  position: relative;
}

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

.gallery-item img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}

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

.footer {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: var(--text);
  padding: 2rem 0;
  text-align: center;
  border-radius: 20px 20px 0 0;
  margin-top: 3rem;
}

.navigation {
  display: flex;
  justify-content: center;
  gap: 1.5rem;
  margin-top: 1.5rem;
}

.nav-link {
  color: var(--text);
  text-decoration: none;
  padding: 0.5rem 1rem;
  border-radius: 4px;
  transition: background-color 0.3s ease;
}

.nav-link:hover {
  background-color: rgba(255,255,255,0.2);
}

@media (max-width: 768px) {
  .header h1 {
    font-size: 2rem;
  }
  
  .header p {
    font-size: 1rem;
  }
  
  .article-section {
    padding: 1.5rem;
  }
  
  .image-gallery {
    grid-template-columns: 1fr;
  }
}

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

.article-section {
  animation: fadeIn 0.6s ease forwards;
}

.article-section:nth-child(2) { animation-delay: 0.1s; }
.article-section:nth-child(3) { animation-delay: 0.2s; }
.article-section:nth-child(4) { animation-delay: 0.3s; }
.article-section:nth-child(5) { animation-delay: 0.4s; }
.article-section:nth-child(6) { animation-delay: 0.5s; }
.article-section:nth-child(7) { animation-delay: 0.6s; }
.article-section:nth-child(8) { animation-delay: 0.7s; }
.article-section:nth-child(9) { animation-delay: 0.8s; }