:root {
  --primary: #0d47a1;
  --secondary: #42a5f5;
  --accent: #ff9800;
  --text: #f5f5f5;
  --card-bg: rgba(255, 255, 255, 0.1);
  --shadow: 0 10px 20px rgba(0, 0, 0, 0.2);
}

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

body {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: var(--text);
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  line-height: 1.6;
  padding: 0;
  margin: 0;
  min-height: 100%;
}

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

.header {
  text-align: center;
  padding: 40px 0;
  position: relative;
  overflow: hidden;
}

.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: -1;
}

.header h1 {
  font-size: 2.5rem;
  margin-bottom: 20px;
  text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
  background: linear-gradient(to right, var(--text), var(--accent));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.notice {
  background: rgba(0, 0, 0, 0.3);
  padding: 15px;
  border-radius: 10px;
  margin: 20px auto;
  max-width: 800px;
  text-align: center;
  border: 1px solid var(--accent);
  box-shadow: var(--shadow);
}

.article-container {
  display: grid;
  grid-template-columns: 250px 1fr;
  gap: 30px;
  margin-top: 40px;
}

.nav-sidebar {
  position: sticky;
  top: 20px;
  height: fit-content;
  background: var(--card-bg);
  backdrop-filter: blur(10px);
  border-radius: 15px;
  padding: 20px;
  box-shadow: var(--shadow);
}

.nav-sidebar h3 {
  color: var(--accent);
  margin-bottom: 15px;
  font-size: 1.2rem;
}

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

.nav-sidebar li {
  margin-bottom: 10px;
}

.nav-sidebar a {
  color: var(--text);
  text-decoration: none;
  transition: all 0.3s;
  display: block;
  padding: 8px 10px;
  border-radius: 5px;
}

.nav-sidebar a:hover {
  background: rgba(255, 255, 255, 0.1);
  color: var(--accent);
  transform: translateX(5px);
}

article {
  background: var(--card-bg);
  backdrop-filter: blur(10px);
  border-radius: 20px;
  padding: 30px;
  box-shadow: var(--shadow);
}

article h2 {
  font-size: 2rem;
  margin-bottom: 20px;
  color: var(--accent);
  position: relative;
  padding-bottom: 10px;
}

article h2::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100px;
  height: 3px;
  background: linear-gradient(to right, var(--accent), transparent);
}

article h3 {
  font-size: 1.5rem;
  margin: 30px 0 15px;
  color: var(--text);
}

article p {
  margin-bottom: 20px;
  font-size: 1.1rem;
}

.image-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
  margin: 30px 0;
}

.image-grid img {
  width: 100%;
  height: 200px;
  object-fit: cover;
  border-radius: 10px;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
  transition: all 0.3s;
}

.image-grid img:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.3);
}

pre {
  background: rgba(0, 0, 0, 0.3);
  border-radius: 10px;
  padding: 20px;
  margin: 20px 0;
  overflow-x: auto;
  font-family: 'Courier New', Courier, monospace;
  position: relative;
  border-left: 3px solid var(--accent);
}

pre::before {
  content: "CSS";
  position: absolute;
  top: 0;
  right: 0;
  background: var(--accent);
  color: #000;
  padding: 5px 10px;
  font-size: 0.8rem;
  border-bottom-left-radius: 5px;
}

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

.card {
  background: rgba(255, 255, 255, 0.1);
  border-radius: 15px;
  padding: 20px;
  margin: 20px 0;
  box-shadow: 7px 7px 20px rgba(0, 0, 0, 0.2),
              -7px -7px 20px rgba(255, 255, 255, 0.05);
  transition: all 0.3s;
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 10px 10px 25px rgba(0, 0, 0, 0.3),
              -10px -10px 25px rgba(255, 255, 255, 0.1);
}

.footer {
  text-align: center;
  padding: 30px;
  margin-top: 50px;
  background: rgba(0, 0, 0, 0.2);
  border-radius: 0 0 20px 20px;
}

@media (max-width: 900px) {
  .article-container {
    grid-template-columns: 1fr;
  }
  
  .nav-sidebar {
    position: static;
    margin-bottom: 30px;
  }
}

@media (max-width: 600px) {
  .header h1 {
    font-size: 2rem;
  }
  
  article {
    padding: 20px;
  }
  
  article h2 {
    font-size: 1.8rem;
  }
  
  article h3 {
    font-size: 1.3rem;
  }
  
  .image-grid {
    grid-template-columns: 1fr;
  }
}

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

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