:root {
  --primary: #1F3A93;
  --secondary: #2ECC71;
  --accent: #F5A623;
  --bg-light: #f8f9fa;
  --bg-dark: #2c3e50;
  --text: #333;
  --text-light: #7f8c8d;
}

@import url('https://fonts.googleapis.com/css2?family=Roboto:wght@700&family=Open+Sans:wght@400;600&display=swap');

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

body {
  font-family: 'Open Sans', sans-serif;
  color: var(--text);
  line-height: 1.6;
  background: linear-gradient(135deg, #f5f7fa 0%, #e4e8eb 100%);
  overflow-x: hidden;
}

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

/* Header Styles */
.header {
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  padding: 20px 0;
  position: fixed;
  width: 100%;
  z-index: 1000;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  color: white;
  font-family: 'Roboto', sans-serif;
  font-size: 24px;
  font-weight: bold;
  text-decoration: none;
}

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

.nav-links a {
  color: white;
  text-decoration: none;
  font-weight: 600;
  position: relative;
  transition: all 0.3s ease;
}

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

.nav-links a::after {
  content: '';
  position: absolute;
  width: 0;
  height: 2px;
  bottom: -5px;
  left: 0;
  background-color: var(--accent);
  transition: width 0.3s ease;
}

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

/* Hero Section */
.hero {
  padding: 180px 0 100px;
  text-align: center;
  background: url('https://images.gptkong.com/demo/sample1.png') center/cover no-repeat;
  position: relative;
}

.hero::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(31, 58, 147, 0.7);
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 800px;
  margin: 0 auto;
}

.hero h1 {
  font-size: 48px;
  color: white;
  margin-bottom: 20px;
  font-family: 'Roboto', sans-serif;
  text-shadow: 0 2px 4px rgba(0,0,0,0.3);
}

.hero p {
  font-size: 20px;
  color: white;
  margin-bottom: 30px;
}

.notice {
  background-color: rgba(255,255,255,0.2);
  padding: 15px;
  border-radius: 8px;
  margin-top: 30px;
  color: white;
  font-weight: 600;
}

/* Main Content */
.main-content {
  padding: 80px 0;
}

.section {
  margin-bottom: 80px;
  background: white;
  border-radius: 12px;
  padding: 40px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.05);
  position: relative;
  overflow: hidden;
}

.section::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 5px;
  height: 100%;
  background: linear-gradient(to bottom, var(--primary), var(--secondary));
}

.section h2 {
  font-size: 32px;
  margin-bottom: 30px;
  color: var(--primary);
  font-family: 'Roboto', sans-serif;
  position: relative;
}

.section h2::after {
  content: '';
  position: absolute;
  bottom: -10px;
  left: 0;
  width: 60px;
  height: 3px;
  background: var(--accent);
}

.section h3 {
  font-size: 24px;
  margin: 30px 0 20px;
  color: var(--bg-dark);
}

.section p {
  margin-bottom: 20px;
  font-size: 16px;
}

.section span {
  color: var(--secondary);
  font-weight: 600;
}

/* Code Blocks */
pre {
  background: #282c34;
  border-radius: 8px;
  padding: 20px;
  margin: 25px 0;
  overflow: auto;
  position: relative;
}

code {
  font-family: 'Courier New', monospace;
  color: #abb2bf;
}

.language-css {
  display: block;
}

/* Image Gallery */
.image-gallery {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 20px;
  margin: 40px 0;
}

.gallery-item {
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 5px 15px rgba(0,0,0,0.1);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.gallery-item:hover {
  transform: translateY(-5px);
  box-shadow: 0 15px 30px rgba(0,0,0,0.15);
}

.gallery-item img {
  width: 100%;
  height: auto;
  display: block;
  transition: transform 0.5s ease;
}

.gallery-item:hover img {
  transform: scale(1.05);
}

/* Footer */
.footer {
  background: linear-gradient(135deg, var(--primary), var(--bg-dark));
  color: white;
  padding: 60px 0 30px;
  text-align: center;
}

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

.footer-links a {
  color: white;
  text-decoration: none;
  transition: color 0.3s ease;
}

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

.copyright {
  margin-top: 30px;
  color: rgba(255,255,255,0.7);
  font-size: 14px;
}

/* Responsive Design */
@media (max-width: 992px) {
  .hero h1 {
    font-size: 36px;
  }
  
  .hero p {
    font-size: 18px;
  }
}

@media (max-width: 768px) {
  .nav-links {
    gap: 15px;
  }
  
  .hero {
    padding: 150px 0 80px;
  }
  
  .hero h1 {
    font-size: 32px;
  }
  
  .section {
    padding: 30px;
  }
  
  .section h2 {
    font-size: 28px;
  }
}

@media (max-width: 576px) {
  .navbar {
    flex-direction: column;
    gap: 15px;
  }
  
  .nav-links {
    flex-wrap: wrap;
    justify-content: center;
  }
  
  .hero {
    padding: 120px 0 60px;
  }
  
  .hero h1 {
    font-size: 28px;
  }
  
  .section {
    padding: 20px;
  }
  
  .image-gallery {
    grid-template-columns: 1fr;
  }
}

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

.section {
  animation: fadeIn 0.6s ease forwards;
}

.section:nth-child(2) { animation-delay: 0.1s; }
.section:nth-child(3) { animation-delay: 0.2s; }
.section:nth-child(4) { animation-delay: 0.3s; }
.section:nth-child(5) { animation-delay: 0.4s; }

/* Tabs */
.tabs {
  display: flex;
  margin-bottom: 20px;
  border-bottom: 1px solid #ddd;
}

.tab {
  padding: 10px 20px;
  cursor: pointer;
  background: #f1f1f1;
  margin-right: 5px;
  border-radius: 5px 5px 0 0;
  transition: all 0.3s ease;
}

.tab.active {
  background: var(--primary);
  color: white;
}

.tab-content {
  display: none;
  padding: 20px;
  background: white;
  border-radius: 0 0 5px 5px;
}

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

/* Accordion */
.accordion {
  margin: 30px 0;
}

.accordion-item {
  margin-bottom: 10px;
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

.accordion-header {
  padding: 15px 20px;
  background: var(--primary);
  color: white;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: background 0.3s ease;
}

.accordion-header:hover {
  background: #172b63;
}

.accordion-content {
  padding: 0;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
  background: white;
}

.accordion-content-inner {
  padding: 20px;
}

.accordion-item.active .accordion-content {
  max-height: 500px;
}

/* Tooltip */
.tooltip {
  position: relative;
  display: inline-block;
  border-bottom: 1px dotted var(--primary);
  cursor: help;
}

.tooltip .tooltiptext {
  visibility: hidden;
  width: 200px;
  background-color: var(--primary);
  color: white;
  text-align: center;
  border-radius: 6px;
  padding: 10px;
  position: absolute;
  z-index: 1;
  bottom: 125%;
  left: 50%;
  transform: translateX(-50%);
  opacity: 0;
  transition: opacity 0.3s;
}

.tooltip:hover .tooltiptext {
  visibility: visible;
  opacity: 1;
}

/* Floating Action Button */
.fab {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 60px;
  height: 60px;
  background: var(--accent);
  color: white;
  border-radius: 50%;
  display: flex;
  justify-content: center;
  align-items: center;
  box-shadow: 0 4px 10px rgba(0,0,0,0.2);
  cursor: pointer;
  transition: all 0.3s ease;
  z-index: 100;
}

.fab:hover {
  transform: scale(1.1);
  box-shadow: 0 6px 15px rgba(0,0,0,0.3);
}

/* Progress Bar */
.progress-container {
  width: 100%;
  height: 8px;
  background: #f1f1f1;
  border-radius: 4px;
  margin: 20px 0;
  overflow: hidden;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  width: 0;
  transition: width 0.3s ease;
}

/* Card */
.card {
  background: white;
  border-radius: 12px;
  padding: 30px;
  box-shadow: 0 5px 15px rgba(0,0,0,0.05);
  margin: 20px 0;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

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

.card-title {
  font-size: 20px;
  margin-bottom: 15px;
  color: var(--primary);
}

.card-text {
  color: var(--text-light);
}

/* Badge */
.badge {
  display: inline-block;
  padding: 5px 10px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: bold;
  background: var(--accent);
  color: white;
  margin-right: 10px;
}

/* Breadcrumb */
.breadcrumb {
  display: flex;
  padding: 15px 0;
  list-style: none;
}

.breadcrumb-item {
  margin-right: 10px;
}

.breadcrumb-item:not(:last-child)::after {
  content: '/';
  margin-left: 10px;
  color: var(--text-light);
}

.breadcrumb-link {
  color: var(--primary);
  text-decoration: none;
}

.breadcrumb-link:hover {
  text-decoration: underline;
}

/* Pagination */
.pagination {
  display: flex;
  justify-content: center;
  margin: 30px 0;
}

.page-item {
  margin: 0 5px;
}

.page-link {
  display: block;
  padding: 8px 15px;
  background: white;
  color: var(--primary);
  text-decoration: none;
  border-radius: 4px;
  transition: all 0.3s ease;
}

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

.page-item.active .page-link {
  background: var(--primary);
  color: white;
}

/* Timeline */
.timeline {
  position: relative;
  max-width: 800px;
  margin: 40px auto;
}

.timeline::before {
  content: '';
  position: absolute;
  width: 2px;
  background: #ddd;
  top: 0;
  bottom: 0;
  left: 50%;
  margin-left: -1px;
}

.timeline-item {
  padding: 20px 40px;
  position: relative;
  width: 50%;
  box-sizing: border-box;
}

.timeline-item:nth-child(odd) {
  left: 0;
}

.timeline-item:nth-child(even) {
  left: 50%;
}

.timeline-dot {
  position: absolute;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent);
  top: 30px;
  right: -8px;
}

.timeline-item:nth-child(even) .timeline-dot {
  left: -8px;
}

.timeline-content {
  padding: 20px;
  background: white;
  border-radius: 8px;
  box-shadow: 0 3px 10px rgba(0,0,0,0.1);
}

.timeline-date {
  color: var(--accent);
  font-weight: bold;
  margin-bottom: 10px;
}

/* Responsive Timeline */
@media (max-width: 768px) {
  .timeline::before {
    left: 40px;
  }
  
  .timeline-item {
    width: 100%;
    padding-left: 70px;
    padding-right: 25px;
  }
  
  .timeline-item:nth-child(even) {
    left: 0;
  }
  
  .timeline-dot {
    left: 32px;
  }
}