:root {
  --primary: #646cff;
  --primary-hover: #535bf2;
  --text-primary: rgba(255, 255, 255, 0.87);
  --text-secondary: #888;
  --bg-primary: #242424;
  --bg-secondary: #1a1a1a;
  --bg-card: #2a2a2a;
  --border: #3a3a3a;
  --success: #4caf50;
  --warning: #ff9800;
  --danger: #f44336;
  --transition: all 0.25s ease;
  --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  --radius: 8px;
  
  font-family: Inter, system-ui, Avenir, Helvetica, Arial, sans-serif;
  line-height: 1.5;
  font-weight: 400;

  color-scheme: light dark;
  color: var(--text-primary);
  background-color: var(--bg-primary);

  font-synthesis: none;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

body {
  margin: 0;
  min-width: 320px;
  min-height: 100vh;
}

a {
  font-weight: 500;
  color: var(--primary);
  text-decoration: inherit;
  transition: var(--transition);
}

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

h1, h2, h3, h4, h5, h6 {
  line-height: 1.2;
  margin-bottom: 1rem;
}

h1 {
  font-size: 2.5rem;
}

h2 {
  font-size: 2rem;
}

h3 {
  font-size: 1.5rem;
}

/* Layout */
.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 1rem;
}

header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background-color: var(--bg-secondary);
  box-shadow: var(--shadow);
  z-index: 100;
}

.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 0;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 1.5rem;
  font-weight: 700;
}

.logo i {
  color: var(--primary);
}

.nav-links {
  display: flex;
  gap: 1.5rem;
}

.nav-links a {
  position: relative;
  color: var(--text-primary);
}

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

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

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

.theme-toggle {
  background: none;
  border: none;
  color: var(--text-primary);
  cursor: pointer;
  font-size: 1.2rem;
}

.hamburger {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  cursor: pointer;
  font-size: 1.5rem;
}

/* Hero Section */
.hero {
  height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: 2rem;
  background: linear-gradient(135deg, var(--bg-primary), var(--bg-secondary));
}

.hero h1 {
  font-size: 3.5rem;
  margin-bottom: 1rem;
  background: linear-gradient(to right, var(--primary), #9f9fff);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  animation: fadeInUp 0.8s ease;
}

.hero p {
  font-size: 1.2rem;
  max-width: 600px;
  margin-bottom: 2rem;
  color: var(--text-secondary);
  animation: fadeInUp 1s ease;
}

.hero-buttons {
  display: flex;
  gap: 1rem;
  animation: fadeInUp 1.2s ease;
}

.btn {
  display: inline-block;
  padding: 0.8rem 1.5rem;
  border-radius: var(--radius);
  font-weight: 500;
  text-align: center;
  cursor: pointer;
  transition: var(--transition);
  border: none;
  font-size: 1rem;
}

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

.btn-primary:hover {
  background-color: var(--primary-hover);
  transform: translateY(-2px);
}

.btn-outline {
  background-color: transparent;
  border: 1px solid var(--primary);
  color: var(--primary);
}

.btn-outline:hover {
  background-color: var(--primary);
  color: white;
  transform: translateY(-2px);
}

/* Page Header */
.page-header {
  padding: 8rem 0 4rem;
  text-align: center;
  background: linear-gradient(135deg, var(--bg-primary), var(--bg-secondary));
}

.page-header h1 {
  font-size: 3rem;
  margin-bottom: 1rem;
  background: linear-gradient(to right, var(--primary), #9f9fff);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.page-header p {
  font-size: 1.2rem;
  max-width: 600px;
  margin: 0 auto;
  color: var(--text-secondary);
}

/* Features Section */
.features {
  padding: 5rem 0;
}

.section-title {
  margin-bottom: 3rem;
  position: relative;
  display: inline-block;
  text-align: center;
  width: 100%;
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: -10px;
  left: 50%;
  transform: translateX(-50%);
  width: 50px;
  height: 3px;
  background-color: var(--primary);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 2rem;
}

.feature-card {
  background-color: var(--bg-card);
  border-radius: var(--radius);
  padding: 2rem;
  text-align: center;
  box-shadow: var(--shadow);
  transition: var(--transition);
  border: 1px solid var(--border);
}

.feature-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.2);
}

.feature-icon {
  font-size: 2.5rem;
  color: var(--primary);
  margin-bottom: 1.5rem;
}

.feature-card h3 {
  margin-bottom: 1rem;
}

.feature-card p {
  color: var(--text-secondary);
}

/* CTA Section */
.cta {
  padding: 5rem 0;
  background-color: var(--bg-secondary);
}

.cta-content {
  text-align: center;
  max-width: 800px;
  margin: 0 auto;
}

.cta h2 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
}

.cta p {
  font-size: 1.2rem;
  margin-bottom: 2rem;
  color: var(--text-secondary);
}

.cta-buttons {
  display: flex;
  justify-content: center;
  gap: 1rem;
}

/* Contact Section */
.contact {
  padding: 5rem 0;
}

.contact-container {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: 3rem;
}

.contact-info {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.contact-item i {
  font-size: 1.5rem;
  color: var(--primary);
}

.contact-form {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.form-group label {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.form-group input,
.form-group textarea {
  padding: 0.8rem;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: inherit;
  resize: vertical;
}

/* Filters Section */
.filters {
  padding: 2rem 0;
  background-color: var(--bg-secondary);
  position: sticky;
  top: 70px;
  z-index: 90;
  box-shadow: var(--shadow);
}

.filters-container {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  align-items: center;
}

.filter-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.filter-group label {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.filter-group select, .search-input {
  padding: 0.5rem;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  min-width: 150px;
}

.search-input {
  flex-grow: 1;
  min-width: 200px;
}

/* Projects Grid */
.projects {
  padding: 2rem 0;
}

.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 2rem;
}

.project-card {
  background-color: var(--bg-card);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
  transition: var(--transition);
  border: 1px solid var(--border);
  position: relative;
}

.project-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.2);
}

.card-header {
  padding: 1.5rem;
  border-bottom: 1px solid var(--border);
}

.card-title {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.5rem;
}

.card-title h3 {
  margin-bottom: 0;
}

.difficulty {
  font-size: 0.8rem;
  padding: 0.2rem 0.5rem;
  border-radius: 20px;
  font-weight: 500;
}

.easy {
  background-color: rgba(76, 175, 80, 0.2);
  color: var(--success);
}

.medium {
  background-color: rgba(255, 152, 0, 0.2);
  color: var(--warning);
}

.hard {
  background-color: rgba(244, 67, 54, 0.2);
  color: var(--danger);
}

.card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1rem;
}

.tag {
  font-size: 0.8rem;
  padding: 0.2rem 0.5rem;
  border-radius: 20px;
  background-color: rgba(100, 108, 255, 0.1);
  color: var(--primary);
}

.card-body {
  padding: 1.5rem;
}

.card-description {
  margin-bottom: 1.5rem;
  color: var(--text-secondary);
}

.code-preview {
  background-color: #282c34;
  border-radius: var(--radius);
  padding: 1rem;
  margin-bottom: 1.5rem;
  overflow-x: auto;
  position: relative;
}

.code-preview pre {
  margin: 0;
  font-family: 'Fira Code', monospace;
  font-size: 0.9rem;
}

.code-preview code {
  font-family: inherit;
}

.card-footer {
  padding: 1.5rem;
  border-top: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.language-badge {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.9rem;
}

.language-badge i {
  font-size: 1.2rem;
}

/* DSA Categories */
.dsa-categories {
  padding: 2rem 0;
}

.category-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin-bottom: 2rem;
}

.tab-btn {
  padding: 0.5rem 1rem;
  border-radius: var(--radius);
  background-color: var(--bg-card);
  color: var(--text-primary);
  border: 1px solid var(--border);
  cursor: pointer;
  transition: var(--transition);
}

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

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

.dsa-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 2rem;
}

.dsa-card {
  background-color: var(--bg-card);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
  transition: var(--transition);
  border: 1px solid var(--border);
}

.dsa-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.2);
}

.dsa-card-header {
  padding: 1.5rem;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.dsa-card-header h3 {
  margin-bottom: 0;
}

.dsa-card-body {
  padding: 1.5rem;
}

.dsa-features {
  list-style: none;
  margin-top: 1rem;
}

.dsa-features li {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.5rem;
}

.dsa-features i.fa-check {
  color: var(--success);
}

.dsa-features i.fa-times {
  color: var(--danger);
}

.dsa-card-footer {
  padding: 1.5rem;
  border-top: 1px solid var(--border);
  text-align: center;
}

/* Learning Path */
.learning-path {
  padding: 5rem 0;
  background-color: var(--bg-secondary);
}

.timeline {
  position: relative;
  max-width: 800px;
  margin: 0 auto;
  padding: 2rem 0;
}

.timeline::before {
  content: '';
  position: absolute;
  top: 0;
  bottom: 0;
  left: 50%;
  width: 2px;
  background-color: var(--primary);
  transform: translateX(-50%);
}

.timeline-item {
  position: relative;
  margin-bottom: 3rem;
}

.timeline-dot {
  position: absolute;
  top: 0;
  left: 50%;
  width: 20px;
  height: 20px;
  background-color: var(--primary);
  border-radius: 50%;
  transform: translateX(-50%);
  z-index: 1;
}

.timeline-content {
  position: relative;
  width: 45%;
  padding: 1.5rem;
  background-color: var(--bg-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.timeline-item:nth-child(odd) .timeline-content {
  margin-left: auto;
}

.timeline-item:nth-child(even) .timeline-content::before {
  content: '';
  position: absolute;
  top: 10px;
  right: -10px;
  width: 20px;
  height: 20px;
  background-color: var(--bg-card);
  transform: rotate(45deg);
}

.timeline-item:nth-child(odd) .timeline-content::before {
  content: '';
  position: absolute;
  top: 10px;
  left: -10px;
  width: 20px;
  height: 20px;
  background-color: var(--bg-card);
  transform: rotate(45deg);
}

/* Footer */
footer {
  background-color: var(--bg-secondary);
  padding: 2rem 0;
  margin-top: 2rem;
}

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

.social-links {
  display: flex;
  gap: 1rem;
}

.social-links a {
  font-size: 1.2rem;
}

/* Modal */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.7);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transition: var(--transition);
}

.modal-overlay.active {
  opacity: 1;
  visibility: visible;
}

.modal {
  background-color: var(--bg-card);
  border-radius: var(--radius);
  width: 90%;
  max-width: 800px;
  max-height: 90vh;
  overflow-y: auto;
  box-shadow: 0 15px 30px rgba(0, 0, 0, 0.3);
  transform: translateY(-20px);
  transition: var(--transition);
}

.modal-overlay.active .modal {
  transform: translateY(0);
}

.modal-header {
  padding: 1.5rem;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.modal-title {
  margin-bottom: 0;
}

.modal-close {
  background: none;
  border: none;
  color: var(--text-secondary);
  font-size: 1.5rem;
  cursor: pointer;
  transition: var(--transition);
}

.modal-close:hover {
  color: var(--danger);
}

.modal-body {
  padding: 1.5rem;
}

.modal-code {
  background-color: #282c34;
  border-radius: var(--radius);
  padding: 1rem;
  margin-bottom: 1.5rem;
  overflow-x: auto;
}

.modal-code pre {
  margin: 0;
  font-family: 'Fira Code', monospace;
}

.modal-footer {
  padding: 1.5rem;
  border-top: 1px solid var(--border);
  display: flex;
  justify-content: flex-end;
  gap: 1rem;
}

/* Tables */
.complexity-table, .comparison-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
}

.complexity-table th, .complexity-table td,
.comparison-table th, .comparison-table td {
  padding: 0.75rem;
  text-align: left;
  border: 1px solid var(--border);
}

.complexity-table th, .comparison-table th {
  background-color: var(--bg-secondary);
}

/* Complexity Chart */
.complexity-chart {
  height: 300px;
  position: relative;
  margin: 2rem 0;
  border-left: 2px solid var(--text-secondary);
  border-bottom: 2px solid var(--text-secondary);
  padding: 1rem;
}

.chart-line {
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 2px;
  opacity: 0.7;
}

.chart-line::before {
  content: attr(class);
  position: absolute;
  right: 0;
  top: -20px;
  font-size: 0.8rem;
}

.o1 {
  height: 10px;
  background-color: #4caf50;
}

.ologn {
  height: 50px;
  background-color: #2196f3;
  clip-path: polygon(0 100%, 100% 60%, 100% 100%);
}

.on {
  height: 150px;
  background-color: #ffeb3b;
  clip-path: polygon(0 100%, 100% 0, 100% 100%);
}

.onlogn {
  height: 200px;
  background-color: #ff9800;
  clip-path: polygon(0 100%, 100% 0, 100% 100%);
}

.on2 {
  height: 250px;
  background-color: #f44336;
  clip-path: polygon(0 100%, 100% 0, 100% 100%);
}

.o2n {
  height: 280px;
  background-color: #9c27b0;
  clip-path: polygon(0 100%, 100% 0, 100% 100%);
}

.ofactorial {
  height: 290px;
  background-color: #e91e63;
  clip-path: polygon(0 100%, 100% 0, 100% 100%);
}

/* Loading State */
.loading {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 200px;
}

.spinner {
  width: 40px;
  height: 40px;
  border: 4px solid rgba(100, 108, 255, 0.1);
  border-radius: 50%;
  border-top-color: var(--primary);
  animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

/* Empty State */
.empty-state {
  text-align: center;
  padding: 3rem 0;
}

.empty-state i {
  font-size: 3rem;
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

.empty-state p {
  color: var(--text-secondary);
}

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

.fade-in {
  animation: fadeIn 0.5s ease;
}

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

/* Light Theme */
body.light-theme {
  --text-primary: #213547;
  --text-secondary: #666;
  --bg-primary: #ffffff;
  --bg-secondary: #f9f9f9;
  --bg-card: #ffffff;
  --border: #e0e0e0;
  --shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
}

/* Responsive */
@media (max-width: 768px) {
  .navbar {
    padding: 1rem;
  }
  
  .nav-links {
    position: fixed;
    top: 70px;
    left: 0;
    right: 0;
    background-color: var(--bg-secondary);
    flex-direction: column;
    padding: 1rem;
    gap: 1rem;
    box-shadow: var(--shadow);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
  }
  
  .nav-links.active {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }
  
  .hamburger {
    display: block;
  }
  
  .hero h1 {
    font-size: 2.5rem;
  }
  
  .filters-container {
    flex-direction: column;
    align-items: stretch;
  }
  
  .filter-group, .search-input {
    width: 100%;
  }
  
  .projects-grid, .dsa-grid {
    grid-template-columns: 1fr;
  }
  
  .footer-content {
    flex-direction: column;
    gap: 1rem;
    text-align: center;
  }
  
  .contact-container {
    grid-template-columns: 1fr;
  }
  
  .timeline::before {
    left: 30px;
  }
  
  .timeline-dot {
    left: 30px;
  }
  
  .timeline-content {
    width: calc(100% - 60px);
    margin-left: 60px !important;
  }
  
  .timeline-item:nth-child(odd) .timeline-content::before,
  .timeline-item:nth-child(even) .timeline-content::before {
    left: -10px;
    right: auto;
  }
}