:root {
  --primary-color: #4a90e2;
  --secondary-color: #f5a623;
  --bg-color: #f8f9fa;
  --text-color: #333;
  --light-gray: #e9ecef;
  --dark-gray: #6c757d;
  --white: #ffffff;
  --transition: all 0.3s ease;
}

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

body {
  font-family: 'Roboto', sans-serif;
  color: var(--text-color);
  background-color: var(--bg-color);
  line-height: 1.6;
  overflow-x: hidden;
}

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

.header {
  background: linear-gradient(135deg, var(--primary-color), #357ab8);
  color: var(--white);
  padding: 2rem 0;
  text-align: center;
  margin-bottom: 3rem;
  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') no-repeat center/cover;
  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(0,0,0,0.2);
}

.header p {
  font-size: 1.2rem;
  max-width: 800px;
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.notice {
  background-color: var(--white);
  padding: 1rem;
  text-align: center;
  margin-bottom: 2rem;
  border-radius: 8px;
  box-shadow: 0 4px 6px rgba(0,0,0,0.1);
  color: var(--primary-color);
  font-weight: bold;
}

article {
  background-color: var(--white);
  padding: 2rem;
  border-radius: 12px;
  box-shadow: 0 8px 16px rgba(0,0,0,0.1);
  margin-bottom: 3rem;
}

article h2 {
  color: var(--primary-color);
  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: 80px;
  height: 3px;
  background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
}

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

article p {
  margin-bottom: 1.5rem;
  font-size: 1.1rem;
}

article pre {
  background-color: #282c34;
  color: #abb2bf;
  padding: 1.5rem;
  border-radius: 8px;
  overflow-x: auto;
  margin: 1.5rem 0;
  box-shadow: 0 4px 8px rgba(0,0,0,0.2);
  position: relative;
}

article pre::before {
  content: "CSS";
  position: absolute;
  top: 0;
  left: 0;
  background-color: var(--primary-color);
  color: white;
  padding: 0.2rem 0.8rem;
  border-radius: 0 0 8px 0;
  font-size: 0.8rem;
}

article code {
  font-family: 'Fira Code', monospace;
  font-size: 0.95rem;
}

article span {
  background-color: var(--light-gray);
  padding: 0.2rem 0.4rem;
  border-radius: 4px;
  font-family: 'Fira Code', monospace;
  font-size: 0.9rem;
}

.color {
  font-weight: bold;
}

.color:nth-child(1) {
  color: var(--primary-color);
}

.color:nth-child(2) {
  color: var(--secondary-color);
}

.gallery {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
  margin: 2rem 0;
}

.gallery img {
  width: 100%;
  height: auto;
  border-radius: 12px;
  box-shadow: 0 4px 8px rgba(0,0,0,0.1);
  transition: var(--transition);
}

.gallery img:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 16px rgba(0,0,0,0.2);
}

.nav-links {
  position: sticky;
  top: 20px;
  background-color: var(--white);
  padding: 1.5rem;
  border-radius: 12px;
  box-shadow: 0 4px 8px rgba(0,0,0,0.1);
  margin-bottom: 2rem;
}

.nav-links h3 {
  color: var(--primary-color);
  margin-bottom: 1rem;
  font-size: 1.2rem;
}

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

.nav-links li {
  margin-bottom: 0.8rem;
}

.nav-links a {
  color: var(--dark-gray);
  text-decoration: none;
  transition: var(--transition);
  display: block;
  padding: 0.5rem 0;
  position: relative;
}

.nav-links a::before {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--primary-color);
  transition: var(--transition);
}

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

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

.content-wrapper {
  display: grid;
  grid-template-columns: 250px 1fr;
  gap: 2rem;
}

@media (max-width: 992px) {
  .content-wrapper {
    grid-template-columns: 1fr;
  }
  
  .nav-links {
    position: static;
  }
}

.footer {
  background: linear-gradient(135deg, var(--primary-color), #357ab8);
  color: var(--white);
  padding: 2rem 0;
  text-align: center;
  margin-top: 3rem;
}

.footer p {
  margin-bottom: 0;
}

.highlight-box {
  background: linear-gradient(45deg, rgba(74,144,226,0.1), rgba(245,166,35,0.1));
  border-left: 4px solid var(--primary-color);
  padding: 1.5rem;
  border-radius: 0 8px 8px 0;
  margin: 2rem 0;
}

.highlight-box h4 {
  color: var(--primary-color);
  margin-bottom: 1rem;
}

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

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

.tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin: 1.5rem 0;
}

.tag {
  background-color: var(--light-gray);
  color: var(--dark-gray);
  padding: 0.4rem 0.8rem;
  border-radius: 20px;
  font-size: 0.8rem;
  transition: var(--transition);
}

.tag:hover {
  background-color: var(--primary-color);
  color: var(--white);
}

.expandable {
  margin: 1.5rem 0;
}

.expandable-summary {
  background-color: var(--light-gray);
  padding: 1rem;
  border-radius: 8px;
  cursor: pointer;
  font-weight: bold;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.expandable-content {
  padding: 1rem;
  background-color: var(--white);
  border-radius: 0 0 8px 8px;
  margin-top: -8px;
  border: 1px solid var(--light-gray);
  border-top: none;
  display: none;
}

.expandable.active .expandable-content {
  display: block;
}

.hexagon-container {
  display: flex;
  justify-content: center;
  margin: 2rem 0;
}

.hexagon {
  width: 150px;
  height: 86.6px;
  background-color: var(--primary-color);
  position: relative;
  margin: 43.3px 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-weight: bold;
}

.hexagon:before,
.hexagon:after {
  content: "";
  position: absolute;
  width: 0;
  border-left: 75px solid transparent;
  border-right: 75px solid transparent;
}

.hexagon:before {
  bottom: 100%;
  border-bottom: 43.3px solid var(--primary-color);
}

.hexagon:after {
  top: 100%;
  border-top: 43.3px solid var(--primary-color);
}