:root {
  --primary: #1E3A8A;
  --secondary: #8B5CF6;
  --accent: #F97316;
  --success: #10B981;
  --light: #F3F4F6;
  --dark: #1F2937;
  --text: #4B5563;
  --white: #FFFFFF;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

body {
  background-color: var(--light);
  color: var(--text);
  line-height: 1.6;
  overflow-x: hidden;
}

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

/* Header Styles */
.header {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: var(--white);
  padding: 2rem 0;
  text-align: center;
  position: relative;
  overflow: hidden;
  margin-bottom: 3rem;
}

.header::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;
}

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

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

/* Navigation */
.nav {
  position: sticky;
  top: 0;
  background: rgba(30, 58, 138, 0.95);
  backdrop-filter: blur(10px);
  z-index: 1000;
  padding: 1rem 0;
  box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

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

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

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

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

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

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -5px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent);
  transition: width 0.3s ease;
}

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

/* Main Content */
.main {
  padding: 2rem 0;
}

.section {
  background: var(--white);
  border-radius: 12px;
  padding: 2rem;
  margin-bottom: 3rem;
  box-shadow: 0 10px 15px -3px rgba(0,0,0,0.1);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.section:hover {
  transform: translateY(-5px);
  box-shadow: 0 20px 25px -5px rgba(0,0,0,0.1);
}

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

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

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

.section p {
  margin-bottom: 1rem;
  font-size: 1.1rem;
}

/* Code Blocks */
pre {
  background: #1E1E1E;
  color: #D4D4D4;
  padding: 1.5rem;
  border-radius: 8px;
  overflow-x: auto;
  margin: 1.5rem 0;
  font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
  font-size: 0.95rem;
  line-height: 1.5;
}

code {
  font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
}

/* Images */
.img-container {
  display: flex;
  flex-wrap: wrap;
  gap: 1.5rem;
  margin: 2rem 0;
  justify-content: center;
}

.img-box {
  width: 300px;
  height: 300px;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 10px 15px -3px rgba(0,0,0,0.1);
  transition: transform 0.3s ease;
}

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

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

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

/* Back to top button */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 50px;
  height: 50px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: var(--white);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s ease;
  box-shadow: 0 4px 6px rgba(0,0,0,0.1);
  z-index: 999;
}

.back-to-top.active {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 15px -3px rgba(0,0,0,0.1);
}

/* Footer */
.footer {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: var(--white);
  padding: 3rem 0;
  text-align: center;
  margin-top: 3rem;
}

.footer p {
  margin-bottom: 1rem;
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: 2rem;
  margin-top: 1.5rem;
}

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

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

/* Responsive */
@media (max-width: 768px) {
  .nav-container {
    flex-direction: column;
    gap: 1rem;
  }
  
  .nav-links {
    flex-wrap: wrap;
    justify-content: center;
  }
  
  .section {
    padding: 1.5rem;
  }
  
  .img-box {
    width: 100%;
    max-width: 300px;
  }
}

@media (max-width: 480px) {
  .header h1 {
    font-size: 2rem;
  }
  
  .header p {
    font-size: 1rem;
  }
  
  .section h2 {
    font-size: 1.5rem;
  }
  
  .section h3 {
    font-size: 1.2rem;
  }
  
  pre {
    padding: 1rem;
    font-size: 0.85rem;
  }
}