:root {
  --primary-dark: #0a2463;
  --primary-light: #3e92cc;
  --accent: #ff7f11;
  --bg-light: #f8f9fa;
  --bg-dark: #1e1e24;
  --text-dark: #2b2d42;
  --text-light: #f8f9fa;
}

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

body {
  background: linear-gradient(135deg, var(--bg-light) 0%, #e6e6e6 100%);
  color: var(--text-dark);
  line-height: 1.6;
  min-height: 100%;
  overflow-x: hidden;
}

header {
  background: linear-gradient(90deg, var(--primary-dark) 0%, var(--primary-light) 100%);
  color: white;
  padding: 2rem 0;
  text-align: center;
  position: relative;
  overflow: hidden;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

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

.header-content {
  position: relative;
  z-index: 1;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 2rem;
}

h1 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
  text-shadow: 0 2px 4px rgba(0,0,0,0.2);
}

.tagline {
  font-size: 1.2rem;
  opacity: 0.9;
  max-width: 800px;
  margin: 0 auto;
}

.nav-container {
  background-color: white;
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

nav {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 2rem;
}

.nav-links {
  display: flex;
  gap: 2rem;
}

.nav-links a {
  color: var(--primary-dark);
  text-decoration: none;
  font-weight: 500;
  padding: 0.5rem 1rem;
  border-radius: 4px;
  transition: all 0.3s ease;
  position: relative;
}

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

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 0;
  height: 2px;
  background: var(--accent);
  transition: width 0.3s ease;
}

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

.main-container {
  max-width: 1200px;
  margin: 2rem auto;
  padding: 0 2rem;
  display: grid;
  grid-template-columns: 1fr;
  gap: 3rem;
}

.hero {
  background: linear-gradient(135deg, rgba(255,255,255,0.9) 0%, rgba(245,245,245,0.9) 100%);
  border-radius: 12px;
  padding: 3rem;
  box-shadow: 0 8px 24px rgba(0,0,0,0.1);
  position: relative;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
}

.hero::before {
  content: "";
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle, rgba(62,146,204,0.05) 0%, rgba(10,36,99,0) 70%);
  z-index: -1;
  animation: rotate 30s linear infinite;
}

@keyframes rotate {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

.hero h2 {
  font-size: 2rem;
  color: var(--primary-dark);
  margin-bottom: 1.5rem;
}

.hero p {
  max-width: 800px;
  margin-bottom: 2rem;
  font-size: 1.1rem;
}

.notice {
  background-color: rgba(255,255,255,0.9);
  border-left: 4px solid var(--accent);
  padding: 1rem;
  margin: 2rem 0;
  border-radius: 0 8px 8px 0;
  box-shadow: 0 2px 8px rgba(0,0,0,0.05);
  font-size: 0.9rem;
}

article {
  background-color: white;
  border-radius: 12px;
  padding: 3rem;
  box-shadow: 0 8px 24px rgba(0,0,0,0.1);
  margin-bottom: 3rem;
}

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

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

article h3 {
  color: var(--primary-dark);
  font-size: 1.5rem;
  margin: 2rem 0 1rem;
}

article p {
  margin-bottom: 1.5rem;
  font-size: 1.05rem;
  line-height: 1.7;
}

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

.image-card {
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  position: relative;
}

.image-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.15);
}

.image-card img {
  width: 100%;
  height: auto;
  display: block;
  transition: transform 0.5s ease;
}

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

.image-card::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(to bottom, rgba(0,0,0,0) 60%, rgba(0,0,0,0.3) 100%);
  z-index: 1;
}

pre {
  background: linear-gradient(135deg, #2b2d42 0%, #1e1e24 100%);
  border-radius: 8px;
  padding: 1.5rem;
  margin: 2rem 0;
  overflow: auto;
  box-shadow: 0 4px 12px rgba(0,0,0,0.2);
  position: relative;
}

code {
  font-family: 'Courier New', monospace;
  color: #f8f9fa;
  font-size: 0.95rem;
  line-height: 1.5;
}

pre::before {
  content: 'CSS3';
  position: absolute;
  top: 0;
  right: 0;
  background: var(--accent);
  color: white;
  padding: 0.25rem 0.75rem;
  border-radius: 0 0 0 8px;
  font-size: 0.8rem;
  font-weight: bold;
}

.split-section {
  display: flex;
  gap: 2rem;
  margin: 3rem 0;
}

.split-section > div {
  flex: 1;
  background: white;
  border-radius: 12px;
  padding: 2rem;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

footer {
  background: linear-gradient(90deg, var(--primary-dark) 0%, var(--primary-light) 100%);
  color: white;
  padding: 3rem 0;
  text-align: center;
  margin-top: 3rem;
}

.footer-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 2rem;
}

@media (max-width: 768px) {
  .nav-links {
    gap: 1rem;
  }
  
  .split-section {
    flex-direction: column;
  }
  
  article {
    padding: 2rem;
  }
  
  .hero {
    padding: 2rem;
  }
}

@media (max-width: 480px) {
  nav {
    flex-direction: column;
    gap: 1rem;
    padding: 1rem;
  }
  
  .nav-links {
    flex-wrap: wrap;
    justify-content: center;
  }
  
  article {
    padding: 1.5rem;
  }
  
  .hero {
    padding: 1.5rem;
  }
}

/* Animation classes */
.fade-in {
  animation: fadeIn 1s ease-in-out;
}

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

.highlight-box {
  background: linear-gradient(135deg, rgba(62,146,204,0.1) 0%, rgba(255,127,17,0.05) 100%);
  border-left: 4px solid var(--accent);
  padding: 1.5rem;
  border-radius: 0 8px 8px 0;
  margin: 2rem 0;
}

.button {
  display: inline-block;
  background: linear-gradient(90deg, var(--accent) 0%, #ff9e3d 100%);
  color: white;
  padding: 0.75rem 1.5rem;
  border-radius: 30px;
  text-decoration: none;
  font-weight: 500;
  box-shadow: 0 4px 8px rgba(255,127,17,0.3);
  transition: all 0.3s ease;
  border: none;
  cursor: pointer;
  margin-top: 1rem;
}

.button:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 12px rgba(255,127,17,0.4);
}

.toc {
  background: white;
  border-radius: 12px;
  padding: 2rem;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
  margin-bottom: 3rem;
}

.toc h3 {
  color: var(--primary-dark);
  margin-bottom: 1rem;
  font-size: 1.3rem;
}

.toc ul {
  list-style: none;
}

.toc li {
  margin-bottom: 0.5rem;
  position: relative;
  padding-left: 1.5rem;
}

.toc li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0.7rem;
  width: 8px;
  height: 8px;
  background: var(--accent);
  border-radius: 50%;
}

.toc a {
  color: var(--primary-dark);
  text-decoration: none;
  transition: color 0.3s ease;
}

.toc a:hover {
  color: var(--accent);
}