:root {
  --primary: #0074D9;
  --secondary: #C0C0C0;
  --accent: #FFA500;
  --dark: #333;
  --light: #f8f9fa;
  --gradient: linear-gradient(135deg, var(--primary) 0%, #1E90FF 100%);
}

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

body {
  font-family: 'Roboto', sans-serif;
  line-height: 1.6;
  letter-spacing: 0.5px;
  color: var(--dark);
  background: var(--light);
  overflow-x: hidden;
}

.header {
  background: var(--gradient);
  color: white;
  padding: 2rem 0;
  text-align: center;
  position: relative;
  overflow: hidden;
  box-shadow: 0 4px 30px 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') center/cover no-repeat;
  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: rgba(255,255,255,0.2);
  backdrop-filter: blur(10px);
  padding: 1rem;
  border-radius: 8px;
  display: inline-block;
  margin-top: 1rem;
  font-size: 0.9rem;
}

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

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
  margin: 3rem 0;
}

.card {
  background: white;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 10px 20px rgba(0,0,0,0.1);
  transition: all 0.3s ease;
  position: relative;
}

.card:hover {
  transform: translateY(-10px);
  box-shadow: 0 15px 30px rgba(0,0,0,0.2);
}

.card-img {
  height: 200px;
  background: var(--secondary);
  position: relative;
  overflow: hidden;
}

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

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

.card-content {
  padding: 1.5rem;
}

.card-content h3 {
  color: var(--primary);
  margin-bottom: 1rem;
  font-size: 1.4rem;
}

.card-content p {
  margin-bottom: 1.5rem;
  color: #555;
}

.tag {
  display: inline-block;
  background: var(--accent);
  color: white;
  padding: 0.3rem 0.8rem;
  border-radius: 20px;
  font-size: 0.8rem;
  margin-right: 0.5rem;
  margin-bottom: 0.5rem;
}

.article {
  background: white;
  border-radius: 12px;
  padding: 2rem;
  box-shadow: 0 5px 15px rgba(0,0,0,0.05);
  margin: 3rem 0;
}

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

.article h2::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100px;
  height: 3px;
  background: var(--accent);
}

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

.article h4 {
  color: var(--primary);
  margin: 1.2rem 0 0.8rem;
  font-size: 1.2rem;
}

.article p {
  margin-bottom: 1rem;
  color: #555;
}

pre {
  background: #f5f5f5;
  border-radius: 8px;
  padding: 1rem;
  overflow-x: auto;
  margin: 1.5rem 0;
  border-left: 4px solid var(--primary);
}

code {
  font-family: 'Courier New', monospace;
  color: #333;
}

.color-sample {
  display: inline-block;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  vertical-align: middle;
  margin: 0 5px;
  box-shadow: 0 2px 5px rgba(0,0,0,0.2);
}

.nav-tabs {
  display: flex;
  list-style: none;
  border-bottom: 1px solid #ddd;
  margin-bottom: 1.5rem;
}

.nav-tabs li {
  margin-right: 1rem;
}

.nav-tabs a {
  display: block;
  padding: 0.5rem 1rem;
  color: #555;
  text-decoration: none;
  border-bottom: 3px solid transparent;
  transition: all 0.3s ease;
}

.nav-tabs a:hover {
  color: var(--primary);
}

.nav-tabs a.active {
  color: var(--primary);
  border-bottom-color: var(--accent);
}

.footer {
  background: var(--dark);
  color: white;
  padding: 2rem 0;
  text-align: center;
  margin-top: 3rem;
}

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

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

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