:root {
  --primary-color: #2c3e50;
  --secondary-color: #34495e;
  --accent-color: #e67e22;
  --background-light: #ecf0f1;
  --background-dark: #bdc3c7;
  --text-color: #2c3e50;
  --text-light: #ecf0f1;
  --shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
  --transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

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

body {
  font-family: 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
  line-height: 1.6;
  color: var(--text-color);
  background: linear-gradient(135deg, var(--background-light), var(--background-dark));
  overflow-x: hidden;
}

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

.header {
  position: relative;
  height: 80px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 40px;
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(10px);
  box-shadow: var(--shadow);
  z-index: 100;
}

.logo {
  font-size: 24px;
  font-weight: 700;
  color: var(--primary-color);
  text-decoration: none;
  display: flex;
  align-items: center;
}

.nav {
  display: flex;
  gap: 30px;
}

.nav-link {
  color: var(--primary-color);
  text-decoration: none;
  font-weight: 500;
  position: relative;
  padding: 5px 0;
  transition: var(--transition);
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent-color);
  transition: var(--transition);
}

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

.hero {
  position: relative;
  padding: 100px 0;
  text-align: center;
  background: linear-gradient(135deg, rgba(44, 62, 80, 0.8), rgba(52, 73, 94, 0.9));
  color: var(--text-light);
  margin-bottom: 60px;
  border-radius: 0 0 20px 20px;
  overflow: hidden;
}

.hero::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: 0.2;
  z-index: -1;
}

.hero h1 {
  font-size: 48px;
  margin-bottom: 20px;
  text-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
}

.hero p {
  font-size: 20px;
  max-width: 800px;
  margin: 0 auto 30px;
  opacity: 0.9;
}

.notice {
  background: rgba(255, 255, 255, 0.2);
  padding: 15px;
  border-radius: 8px;
  display: inline-block;
  margin-top: 30px;
  backdrop-filter: blur(5px);
  border: 1px solid rgba(255, 255, 255, 0.1);
}

.article-container {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 40px;
  margin: 60px auto;
}

article {
  background: white;
  padding: 40px;
  border-radius: 15px;
  box-shadow: var(--shadow);
  position: relative;
  overflow: hidden;
}

article::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 5px;
  height: 100%;
  background: linear-gradient(to bottom, var(--accent-color), #d35400);
}

article h2 {
  color: var(--primary-color);
  margin: 30px 0 20px;
  font-size: 28px;
  position: relative;
  padding-left: 15px;
}

article h2::before {
  content: '';
  position: absolute;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 5px;
  height: 30px;
  background: var(--accent-color);
  border-radius: 3px;
}

article h3 {
  color: var(--secondary-color);
  margin: 25px 0 15px;
  font-size: 22px;
}

article p {
  margin-bottom: 20px;
  font-size: 17px;
  line-height: 1.7;
}

pre {
  background: #2c3e50;
  color: #ecf0f1;
  padding: 20px;
  border-radius: 8px;
  overflow-x: auto;
  margin: 25px 0;
  box-shadow: inset 0 0 10px rgba(0, 0, 0, 0.3);
  position: relative;
}

pre::before {
  content: 'CSS';
  position: absolute;
  top: 0;
  right: 0;
  background: var(--accent-color);
  color: white;
  padding: 3px 10px;
  font-size: 12px;
  border-radius: 0 0 0 5px;
}

code {
  font-family: 'Fira Code', monospace;
  font-size: 15px;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 25px 0;
  box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
}

th, td {
  padding: 15px;
  text-align: left;
  border-bottom: 1px solid #ddd;
}

th {
  background: var(--primary-color);
  color: white;
}

tr:nth-child(even) {
  background: #f8f9fa;
}

tr:hover {
  background: #e9ecef;
}

.sidebar {
  position: sticky;
  top: 100px;
  height: fit-content;
}

.sidebar-card {
  background: white;
  padding: 25px;
  border-radius: 15px;
  box-shadow: var(--shadow);
  margin-bottom: 30px;
}

.sidebar-card h3 {
  color: var(--primary-color);
  margin-bottom: 20px;
  font-size: 20px;
  position: relative;
  padding-bottom: 10px;
}

.sidebar-card h3::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 50px;
  height: 3px;
  background: var(--accent-color);
}

.sidebar-nav {
  list-style: none;
}

.sidebar-nav li {
  margin-bottom: 15px;
}

.sidebar-nav a {
  color: var(--text-color);
  text-decoration: none;
  display: block;
  padding: 10px;
  border-radius: 5px;
  transition: var(--transition);
  position: relative;
  padding-left: 20px;
}

.sidebar-nav a::before {
  content: '';
  position: absolute;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 6px;
  height: 6px;
  background: var(--accent-color);
  border-radius: 50%;
  transition: var(--transition);
}

.sidebar-nav a:hover {
  background: #f8f9fa;
  padding-left: 25px;
}

.sidebar-nav a:hover::before {
  width: 8px;
  height: 8px;
}

.image-gallery {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 15px;
  margin-top: 20px;
}

.gallery-image {
  width: 100%;
  height: 140px;
  object-fit: cover;
  border-radius: 8px;
  box-shadow: 0 3px 10px rgba(0, 0, 0, 0.1);
  transition: var(--transition);
}

.gallery-image:hover {
  transform: translateY(-5px);
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
}

.footer {
  background: var(--primary-color);
  color: var(--text-light);
  padding: 50px 0;
  text-align: center;
  margin-top: 80px;
}

.footer p {
  opacity: 0.8;
  margin-bottom: 20px;
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: 30px;
  margin-bottom: 30px;
}

.footer-link {
  color: var(--text-light);
  text-decoration: none;
  transition: var(--transition);
}

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

@media (max-width: 992px) {
  .article-container {
    grid-template-columns: 1fr;
  }
  
  .sidebar {
    position: static;
    margin-top: 50px;
  }
}

@media (max-width: 768px) {
  .header {
    padding: 0 20px;
  }
  
  .nav {
    gap: 15px;
  }
  
  .hero h1 {
    font-size: 36px;
  }
  
  .hero p {
    font-size: 18px;
  }
  
  article {
    padding: 30px 20px;
  }
}

@media (max-width: 576px) {
  .nav {
    display: none;
  }
  
  .hero {
    padding: 80px 0;
  }
  
  .hero h1 {
    font-size: 28px;
  }
  
  .image-gallery {
    grid-template-columns: 1fr;
  }
}

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

.animate {
  animation: fadeIn 0.8s ease-out forwards;
}

.delay-1 {
  animation-delay: 0.2s;
}

.delay-2 {
  animation-delay: 0.4s;
}

/* Special elements */
.highlight {
  background: linear-gradient(120deg, rgba(230, 126, 34, 0.2), rgba(230, 126, 34, 0));
  padding: 2px 5px;
  border-radius: 3px;
}

.button {
  display: inline-block;
  background: var(--accent-color);
  color: white;
  padding: 12px 25px;
  border-radius: 30px;
  text-decoration: none;
  font-weight: 500;
  transition: var(--transition);
  box-shadow: 0 4px 15px rgba(230, 126, 34, 0.3);
  position: relative;
  overflow: hidden;
}

.button::after {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
  transition: 0.5s;
}

.button:hover {
  transform: translateY(-3px);
  box-shadow: 0 6px 20px rgba(230, 126, 34, 0.4);
}

.button:hover::after {
  left: 100%;
}

.card {
  background: white;
  border-radius: 10px;
  padding: 25px;
  box-shadow: var(--shadow);
  transition: var(--transition);
  margin-bottom: 30px;
}

.card:hover {
  transform: translateY(-10px);
  box-shadow: 0 15px 30px rgba(0, 0, 0, 0.1);
}

.card-image {
  width: 100%;
  height: 180px;
  object-fit: cover;
  border-radius: 8px;
  margin-bottom: 20px;
}

.security-banner {
  background-color: rgba(44, 62, 80, 0.9);
  color: #ecf0f1;
  padding: 15px;
  border-radius: 8px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  transition: box-shadow 0.3s ease;
  margin: 20px 0;
}

.security-banner:hover {
  box-shadow: 0 6px 12px rgba(0, 0, 0, 0.2);
}

.animated-element {
  display: inline-block;
  animation: float 3s ease-in-out infinite;
}

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