:root {
  --primary: #1E3A85;
  --secondary: #FFAB00;
  --accent: #34C759;
  --bg-light: #F7FAFC;
  --bg-white: #FFFFFF;
  --text-dark: #1A202C;
  --text-light: #718096;
}

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

body {
  background: linear-gradient(to bottom, var(--bg-light), var(--bg-white));
  color: var(--text-dark);
  line-height: 1.6;
  min-height: 100%;
  overflow-x: hidden;
}

.header {
  position: relative;
  height: 80vh;
  max-height: 800px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: 2rem;
  background: radial-gradient(circle at 30% 50%, rgba(30, 58, 133, 0.1), transparent 60%),
              linear-gradient(to bottom, transparent, var(--bg-white) 90%);
}

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

.header h1 {
  font-size: clamp(2.5rem, 5vw, 4rem);
  margin-bottom: 1.5rem;
  background: linear-gradient(to right, var(--primary), var(--accent));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  text-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.header p {
  font-size: 1.25rem;
  max-width: 800px;
  margin: 0 auto 2rem;
  color: var(--text-light);
}

.notice {
  position: fixed;
  bottom: 20px;
  right: 20px;
  background: var(--primary);
  color: white;
  padding: 12px 20px;
  border-radius: 8px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
  z-index: 100;
  font-size: 0.9rem;
}

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

.section {
  margin-bottom: 4rem;
  position: relative;
}

.section::after {
  content: "";
  display: block;
  width: 100px;
  height: 4px;
  background: linear-gradient(to right, var(--secondary), var(--accent));
  margin: 2rem auto 0;
  border-radius: 2px;
}

h2 {
  font-size: 2rem;
  margin-bottom: 1.5rem;
  color: var(--primary);
  position: relative;
  display: inline-block;
}

h2::after {
  content: "";
  position: absolute;
  bottom: -8px;
  left: 0;
  width: 50%;
  height: 3px;
  background: var(--secondary);
  border-radius: 3px;
}

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

p {
  margin-bottom: 1.25rem;
  font-size: 1.1rem;
  line-height: 1.7;
}

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

.card {
  background: var(--bg-white);
  border-radius: 12px;
  padding: 2rem;
  box-shadow: 0 10px 20px rgba(0,0,0,0.05);
  transition: all 0.3s ease;
  border: 1px solid rgba(0,0,0,0.05);
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 0 15px 30px rgba(0,0,0,0.1);
}

.card img {
  width: 100%;
  border-radius: 8px;
  margin-bottom: 1.5rem;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
  transition: transform 0.3s ease;
}

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

pre {
  background: #2D3748;
  color: #E2E8F0;
  padding: 1.5rem;
  border-radius: 8px;
  overflow-x: auto;
  margin: 1.5rem 0;
  font-size: 0.95rem;
  line-height: 1.5;
  position: relative;
}

pre::before {
  content: "CSS";
  position: absolute;
  top: 0;
  left: 0;
  background: var(--secondary);
  color: white;
  padding: 0.25rem 0.75rem;
  border-radius: 8px 0 8px 0;
  font-size: 0.8rem;
}

code {
  font-family: 'Fira Code', monospace;
  background: rgba(45, 55, 72, 0.1);
  padding: 0.2rem 0.4rem;
  border-radius: 4px;
  font-size: 0.9rem;
}

.nav-tabs {
  display: flex;
  gap: 1rem;
  margin-bottom: 2rem;
  border-bottom: 1px solid rgba(0,0,0,0.1);
  padding-bottom: 0.5rem;
}

.nav-tabs a {
  text-decoration: none;
  color: var(--text-light);
  padding: 0.5rem 1rem;
  border-radius: 6px;
  transition: all 0.3s ease;
}

.nav-tabs a:hover {
  color: var(--primary);
  background: rgba(30, 58, 133, 0.1);
}

.image-gallery {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 1.5rem;
  margin: 2rem 0;
}

.image-gallery img {
  width: 100%;
  height: 200px;
  object-fit: cover;
  border-radius: 8px;
  box-shadow: 0 4px 8px rgba(0,0,0,0.1);
  transition: all 0.3s ease;
}

.image-gallery img:hover {
  transform: scale(1.05);
  box-shadow: 0 8px 16px rgba(0,0,0,0.15);
}

@media (max-width: 768px) {
  .header {
    height: auto;
    padding: 4rem 1rem;
  }
  
  .card-grid {
    grid-template-columns: 1fr;
  }
  
  .main-content {
    padding: 1rem;
  }
}

@keyframes float {
  0%, 100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(-10px);
  }
}

.floating {
  animation: float 3s ease-in-out infinite;
}