:root {
  /* Color Scheme - Brand Colors */
  --scheme-brand-100: #08002f;
  --scheme-brand-200: #04025c;
  --scheme-brand-300: #1f398e;
  --scheme-brand-400: #3856ae;
  --scheme-brand-500: #5071cc;
  --scheme-brand-600: #6f94f1;
  --scheme-brand-700: #8db3ff;
  --scheme-brand-800: #b2dbff;
  --scheme-brand-900: #bfe8ff;
  --scheme-brand-1000: #ccf6ff;
  --scheme-brand-1100: #d2fcff;
  --scheme-brand-1200: #d2fcff;
  --scheme-brand-600-10: rgba(111,148,241,0.1);
  --scheme-brand-600-30: rgba(111,148,241,0.3);
  --scheme-brand-600-50: rgba(111,148,241,0.5);

  /* Accent Colors */
  --scheme-accent-100: #030b10;
  --scheme-accent-200: #0d181d;
  --scheme-accent-300: #364248;
  --scheme-accent-400: #505d64;
  --scheme-accent-500: #69777e;
  --scheme-accent-600: #8a989f;
  --scheme-accent-700: #a8b7bf;
  --scheme-accent-800: #c8d7df;
  --scheme-accent-900: #d5e4ec;
  --scheme-accent-1000: #e2f1f9;
  --scheme-accent-1100: #e9f8ff;
  --scheme-accent-1200: #efffff;
  --scheme-accent-600-10: rgba(138,152,159,0.1);
  --scheme-accent-600-30: rgba(138,152,159,0.3);
  --scheme-accent-600-50: rgba(138,152,159,0.5);

  /* Neutral Colors */
  --scheme-neutral-100: #020b10;
  --scheme-neutral-200: #0b181d;
  --scheme-neutral-300: #344248;
  --scheme-neutral-400: #4f5d64;
  --scheme-neutral-500: #68777e;
  --scheme-neutral-600: #89989f;
  --scheme-neutral-700: #a7b7be;
  --scheme-neutral-800: #c7d7df;
  --scheme-neutral-900: #d4e4ec;
  --scheme-neutral-1000: #e1f2f9;
  --scheme-neutral-1100: #e7f8ff;
  --scheme-neutral-1200: #eeffff;
  --scheme-neutral-600-10: rgba(137,152,159,0.1);
  --scheme-neutral-600-30: rgba(137,152,159,0.3);
  --scheme-neutral-600-50: rgba(137,152,159,0.5);

  /* Status Colors */
  --color-success: #10b981;
  --color-warning: #f59e0b;
  --color-error: #ef4444;
  --color-info: #3b82f6;

  /* Typography */
  --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;

  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  --spacing-3xl: 4rem;

  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);

  /* Transitions */
  --transition-fast: 0.15s ease-in-out;
  --transition-normal: 0.3s ease-in-out;
  --transition-slow: 0.5s ease-in-out;

  /* Z-index */
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-modal: 300;
  --z-toast: 400;
}

/* Reset & Base Styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-primary);
  font-size: var(--font-size-base);
  line-height: 1.6;
  color: var(--scheme-neutral-200);
  background: linear-gradient(135deg, var(--scheme-neutral-1200) 0%, var(--scheme-accent-1100) 100%);
  min-height: 100vh;
}

/* Container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

/* Header */
.header {
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--scheme-neutral-900);
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  transition: all var(--transition-normal);
}

.header-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--spacing-lg) 0;
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  color: var(--scheme-brand-400);
  text-decoration: none;
}

.logo i {
  font-size: var(--font-size-2xl);
}

.logo h1 {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--scheme-neutral-200);
}

.nav {
  display: flex;
  align-items: center;
  gap: var(--spacing-xl);
}

.nav-link {
  color: var(--scheme-neutral-400);
  text-decoration: none;
  font-weight: 500;
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  position: relative;
}

.nav-link:hover {
  color: var(--scheme-brand-500);
  background: var(--scheme-brand-600-10);
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 50%;
  width: 0;
  height: 2px;
  background: var(--scheme-brand-500);
  transition: all var(--transition-fast);
  transform: translateX(-50%);
}

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

/* Mobile Menu */
.mobile-menu-btn {
  display: none;
  flex-direction: column;
  gap: 4px;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--spacing-sm);
}

.mobile-menu-btn span {
  width: 24px;
  height: 2px;
  background: var(--scheme-neutral-400);
  transition: all var(--transition-fast);
}

/* Hero Section */
.hero {
  background: linear-gradient(135deg, var(--scheme-brand-600-10) 0%, var(--scheme-accent-600-10) 100%);
  padding: var(--spacing-3xl) 0;
  text-align: center;
}

.hero-content {
  max-width: 800px;
  margin: 0 auto;
}

.hero-title {
  font-size: var(--font-size-4xl);
  font-weight: 700;
  color: var(--scheme-neutral-200);
  margin-bottom: var(--spacing-lg);
  background: linear-gradient(135deg, var(--scheme-brand-400), var(--scheme-accent-400));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-description {
  font-size: var(--font-size-lg);
  color: var(--scheme-neutral-400);
  margin-bottom: var(--spacing-2xl);
  line-height: 1.7;
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: var(--spacing-2xl);
  flex-wrap: wrap;
}

.stat-item {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  color: var(--scheme-brand-500);
  font-weight: 500;
}

.stat-item i {
  font-size: var(--font-size-lg);
}

/* Main Sections */
.section {
  padding: var(--spacing-3xl) 0;
}

.section-alt {
  background: rgba(255, 255, 255, 0.3);
}

.section-header {
  display: flex;
  align-items: center;
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-3xl);
  text-align: left;
}

.section-icon {
  width: 80px;
  height: 80px;
  background: linear-gradient(135deg, var(--scheme-brand-500), var(--scheme-brand-600));
  border-radius: var(--radius-xl);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: var(--font-size-2xl);
  box-shadow: var(--shadow-lg);
  flex-shrink: 0;
}

.section-title {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  color: var(--scheme-neutral-200);
  margin-bottom: var(--spacing-xs);
}

.section-subtitle {
  font-size: var(--font-size-lg);
  color: var(--scheme-neutral-400);
  font-weight: 500;
}

/* Content Grid */
.content-grid {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: var(--spacing-2xl);
  margin-bottom: var(--spacing-2xl);
}

/* Cards */
.theory-card,
.demo-card,
.applications-card,
.example-card {
  background: rgba(255, 255, 255, 0.8);
  backdrop-filter: blur(10px);
  border: 1px solid var(--scheme-neutral-900);
  border-radius: var(--radius-xl);
  padding: var(--spacing-2xl);
  box-shadow: var(--shadow-md);
  transition: all var(--transition-normal);
}

.theory-card:hover,
.demo-card:hover,
.applications-card:hover,
.example-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-xl);
}

.theory-card h3,
.demo-card h3,
.applications-card h3,
.example-card h3 {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: var(--font-size-xl);
  font-weight: 600;
  color: var(--scheme-neutral-200);
  margin-bottom: var(--spacing-lg);
}

.theory-card h3 i {
  color: var(--scheme-brand-500);
}

.demo-card h3 i {
  color: var(--color-success);
}

.applications-card h3 i {
  color: var(--scheme-accent-400);
}

/* Theory Features */
.theory-features {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  margin-top: var(--spacing-lg);
}

.feature {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  padding: var(--spacing-md);
  background: var(--scheme-brand-600-10);
  border-radius: var(--radius-md);
  border-left: 4px solid var(--scheme-brand-500);
}

.feature i {
  color: var(--scheme-brand-500);
  font-size: var(--font-size-lg);
}

.feature span {
  font-weight: 500;
  color: var(--scheme-neutral-300);
}

/* Controls */
.controls {
  margin-bottom: var(--spacing-2xl);
}

.input-group {
  display: flex;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
}

.input-group input {
  flex: 1;
  padding: var(--spacing-md) var(--spacing-lg);
  border: 2px solid var(--scheme-neutral-800);
  border-radius: var(--radius-md);
  font-size: var(--font-size-base);
  background: rgba(255, 255, 255, 0.9);
  transition: all var(--transition-fast);
}

.input-group input:focus {
  outline: none;
  border-color: var(--scheme-brand-500);
  box-shadow: 0 0 0 3px var(--scheme-brand-600-10);
}

.button-group {
  display: flex;
  gap: var(--spacing-md);
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-md) var(--spacing-lg);
  font-size: var(--font-size-sm);
  font-weight: 500;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
  white-space: nowrap;
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.btn-primary {
  background: var(--scheme-brand-500);
  color: white;
}

.btn-primary:hover:not(:disabled) {
  background: var(--scheme-brand-400);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

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

.btn-danger:hover:not(:disabled) {
  background: #dc2626;
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

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

.btn-info:hover:not(:disabled) {
  background: #2563eb;
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

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

.btn-warning:hover:not(:disabled) {
  background: #d97706;
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-secondary {
  background: var(--scheme-neutral-600);
  color: white;
}

.btn-secondary:hover:not(:disabled) {
  background: var(--scheme-neutral-500);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

/* Visualization Container */
.visualization-container {
  position: relative;
  background: rgba(255, 255, 255, 0.9);
  border: 2px solid var(--scheme-neutral-900);
  border-radius: var(--radius-lg);
  padding: var(--spacing-2xl);
  margin-bottom: var(--spacing-xl);
  min-height: 300px;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Stack Visualization */
.stack-visualization {
  display: flex;
  flex-direction: column-reverse;
  align-items: center;
  gap: var(--spacing-xs);
  min-height: 200px;
  justify-content: flex-end;
  position: relative;
}

.stack-item {
  background: linear-gradient(135deg, var(--scheme-brand-500), var(--scheme-brand-600));
  color: white;
  padding: var(--spacing-md) var(--spacing-xl);
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: var(--font-size-base);
  min-width: 120px;
  text-align: center;
  box-shadow: var(--shadow-md);
  animation: stackItemEnter var(--transition-normal) ease-out;
  transition: all var(--transition-fast);
}

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

.stack-item.removing {
  animation: stackItemExit var(--transition-normal) ease-in;
}

.stack-pointer {
  position: absolute;
  right: -40px;
  top: 50%;
  transform: translateY(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-sm);
  color: var(--scheme-brand-500);
  font-weight: 600;
}

.stack-pointer i {
  font-size: var(--font-size-lg);
}

/* Queue Visualization */
.queue-visualization {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  min-height: 100px;
  min-width: 100%;
  justify-content: center;
}

.queue-item {
  background: linear-gradient(135deg, var(--scheme-accent-400), var(--scheme-accent-500));
  color: white;
  padding: var(--spacing-lg);
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: var(--font-size-base);
  min-width: 80px;
  text-align: center;
  box-shadow: var(--shadow-md);
  animation: queueItemEnter var(--transition-normal) ease-out;
  transition: all var(--transition-fast);
}

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

.queue-item.removing {
  animation: queueItemExit var(--transition-normal) ease-in;
}

.queue-labels {
  display: flex;
  justify-content: space-between;
  margin-bottom: var(--spacing-md);
  padding: 0 var(--spacing-md);
}

.queue-label {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  color: var(--scheme-accent-500);
  font-weight: 600;
  font-size: var(--font-size-sm);
}

/* Empty State */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-md);
  color: var(--scheme-neutral-500);
  text-align: center;
}

.empty-state i {
  font-size: var(--font-size-3xl);
  opacity: 0.5;
}

.empty-state p {
  font-size: var(--font-size-lg);
  font-weight: 600;
}

.empty-state span {
  font-size: var(--font-size-sm);
  opacity: 0.8;
}

/* Status Panel */
.status-panel {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: var(--spacing-lg);
  background: var(--scheme-neutral-1000);
  border-radius: var(--radius-md);
  padding: var(--spacing-lg);
  border: 1px solid var(--scheme-neutral-900);
}

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

.status-item label {
  font-weight: 600;
  color: var(--scheme-neutral-400);
  font-size: var(--font-size-sm);
}

.status-item span {
  font-weight: 700;
  color: var(--scheme-neutral-200);
}

.status-empty {
  color: var(--color-warning) !important;
}

.status-active {
  color: var(--color-success) !important;
}

/* Applications Grid */
.applications-card {
  grid-column: 1 / -1;
}

.applications-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-xl);
  margin-top: var(--spacing-lg);
}

.application-item {
  background: var(--scheme-neutral-1100);
  padding: var(--spacing-xl);
  border-radius: var(--radius-lg);
  text-align: center;
  border: 1px solid var(--scheme-neutral-900);
  transition: all var(--transition-normal);
}

.application-item:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  background: rgba(255, 255, 255, 0.9);
}

.application-item i {
  font-size: var(--font-size-2xl);
  color: var(--scheme-brand-500);
  margin-bottom: var(--spacing-md);
}

.application-item h4 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--scheme-neutral-200);
  margin-bottom: var(--spacing-sm);
}

.application-item p {
  color: var(--scheme-neutral-400);
  font-size: var(--font-size-sm);
}

/* Examples Section */
.examples-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: var(--spacing-2xl);
}

.example-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: var(--spacing-lg);
}

.example-header h3 {
  flex: 1;
}

.difficulty {
  padding: var(--spacing-xs) var(--spacing-md);
  border-radius: var(--radius-sm);
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.difficulty-easy {
  background: var(--color-success);
  color: white;
}

.difficulty-medium {
  background: var(--color-warning);
  color: white;
}

.difficulty-hard {
  background: var(--color-error);
  color: white;
}

/* Example Demo Styles */
.example-demo {
  margin-top: var(--spacing-lg);
}

.result {
  margin-top: var(--spacing-lg);
  padding: var(--spacing-md);
  border-radius: var(--radius-md);
  font-weight: 600;
  text-align: center;
  transition: all var(--transition-normal);
}

.result.success {
  background: rgba(16, 185, 129, 0.1);
  color: var(--color-success);
  border: 1px solid rgba(16, 185, 129, 0.3);
}

.result.error {
  background: rgba(239, 68, 68, 0.1);
  color: var(--color-error);
  border: 1px solid rgba(239, 68, 68, 0.3);
}

/* Graph Container */
.graph-container {
  background: var(--scheme-neutral-1100);
  border-radius: var(--radius-md);
  padding: var(--spacing-xl);
  margin-bottom: var(--spacing-lg);
  min-height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--scheme-neutral-900);
}

/* Text Editor */
.editor-container {
  background: var(--scheme-neutral-1100);
  border-radius: var(--radius-md);
  border: 1px solid var(--scheme-neutral-900);
  overflow: hidden;
}

#textEditor {
  width: 100%;
  min-height: 200px;
  padding: var(--spacing-lg);
  border: none;
  background: transparent;
  resize: vertical;
  font-family: 'Monaco', 'Menlo', monospace;
  font-size: var(--font-size-sm);
  line-height: 1.5;
}

#textEditor:focus {
  outline: none;
}

.editor-controls {
  display: flex;
  gap: var(--spacing-sm);
  padding: var(--spacing-md);
  background: var(--scheme-neutral-1000);
  border-top: 1px solid var(--scheme-neutral-900);
}

/* Footer */
.footer {
  background: var(--scheme-neutral-200);
  color: var(--scheme-neutral-1000);
  padding: var(--spacing-2xl) 0 var(--spacing-lg);
  margin-top: var(--spacing-3xl);
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: var(--spacing-xl);
}

.footer-info h3 {
  font-size: var(--font-size-xl);
  margin-bottom: var(--spacing-sm);
}

.footer-info p {
  color: var(--scheme-neutral-700);
}

.footer-links {
  display: flex;
  gap: var(--spacing-lg);
}

.footer-links a {
  color: var(--scheme-neutral-700);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: var(--scheme-neutral-1000);
}

.footer-bottom {
  text-align: center;
  padding-top: var(--spacing-lg);
  border-top: 1px solid var(--scheme-neutral-400);
  color: var(--scheme-neutral-600);
}

/* Toast Notification */
.toast {
  position: fixed;
  top: var(--spacing-xl);
  right: var(--spacing-xl);
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  padding: var(--spacing-lg);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-xl);
  border: 1px solid var(--scheme-neutral-900);
  z-index: var(--z-toast);
  transform: translateX(100%);
  opacity: 0;
  transition: all var(--transition-normal);
  max-width: 400px;
}

.toast.show {
  transform: translateX(0);
  opacity: 1;
}

.toast-content {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.toast-icon {
  font-size: var(--font-size-lg);
}

.toast-message {
  font-weight: 500;
  color: var(--scheme-neutral-300);
}

.toast.success .toast-icon {
  color: var(--color-success);
}

.toast.error .toast-icon {
  color: var(--color-error);
}

.toast.info .toast-icon {
  color: var(--color-info);
}

.toast.warning .toast-icon {
  color: var(--color-warning);
}

/* Animations */
@keyframes stackItemEnter {
  from {
    opacity: 0;
    transform: translateY(-20px) scale(0.8);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

@keyframes stackItemExit {
  from {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
  to {
    opacity: 0;
    transform: translateY(-20px) scale(0.8);
  }
}

@keyframes queueItemEnter {
  from {
    opacity: 0;
    transform: translateX(-20px) scale(0.8);
  }
  to {
    opacity: 1;
    transform: translateX(0) scale(1);
  }
}

@keyframes queueItemExit {
  from {
    opacity: 1;
    transform: translateX(0) scale(1);
  }
  to {
    opacity: 0;
    transform: translateX(-20px) scale(0.8);
  }
}

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

@keyframes pulse {
  0% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.05);
  }
  100% {
    transform: scale(1);
  }
}

/* Responsive Design */
@media (max-width: 1024px) {
  .container {
    padding: 0 var(--spacing-md);
  }

  .content-grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-xl);
  }

  .hero-stats {
    gap: var(--spacing-lg);
  }

  .examples-grid {
    grid-template-columns: 1fr;
  }

  .applications-grid {
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  }
}

@media (max-width: 768px) {
  .nav {
    display: none;
  }

  .mobile-menu-btn {
    display: flex;
  }

  .section-header {
    flex-direction: column;
    text-align: center;
    gap: var(--spacing-md);
  }

  .section-icon {
    width: 60px;
    height: 60px;
    font-size: var(--font-size-xl);
  }

  .hero-title {
    font-size: var(--font-size-3xl);
  }

  .hero-description {
    font-size: var(--font-size-base);
  }

  .hero-stats {
    flex-direction: column;
    gap: var(--spacing-md);
  }

  .button-group {
    flex-direction: column;
  }

  .btn {
    justify-content: center;
  }

  .input-group {
    flex-direction: column;
  }

  .status-panel {
    grid-template-columns: 1fr;
  }

  .footer-content {
    flex-direction: column;
    gap: var(--spacing-xl);
    text-align: center;
  }

  .footer-links {
    justify-content: center;
  }

  .toast {
    top: var(--spacing-md);
    right: var(--spacing-md);
    left: var(--spacing-md);
    max-width: none;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--spacing-sm);
  }

  .header-content {
    padding: var(--spacing-md) 0;
  }

  .logo h1 {
    font-size: var(--font-size-lg);
  }

  .hero {
    padding: var(--spacing-2xl) 0;
  }

  .hero-title {
    font-size: var(--font-size-2xl);
  }

  .section {
    padding: var(--spacing-2xl) 0;
  }

  .section-title {
    font-size: var(--font-size-2xl);
  }

  .theory-card,
  .demo-card,
  .applications-card,
  .example-card {
    padding: var(--spacing-lg);
  }

  .visualization-container {
    padding: var(--spacing-lg);
    min-height: 250px;
  }

  .stack-pointer {
    right: -40px;
    font-size: var(--font-size-xs);
  }

  .queue-labels {
    font-size: var(--font-size-xs);
  }

  .applications-grid {
    grid-template-columns: 1fr;
  }

  .application-item {
    padding: var(--spacing-lg);
  }
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  :root {
    --scheme-brand-500: #0066cc;
    --scheme-brand-600: #004499;
    --scheme-neutral-200: #000000;
    --scheme-neutral-400: #333333;
    --scheme-neutral-600: #666666;
  }

  .btn {
    border: 2px solid currentColor;
  }

  .visualization-container {
    border-width: 3px;
  }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  .stack-item,
  .queue-item {
    animation: none !important;
  }

  .btn:hover {
    transform: none !important;
  }

  .theory-card:hover,
  .demo-card:hover,
  .applications-card:hover,
  .example-card:hover,
  .application-item:hover {
    transform: none !important;
  }
}

/* Print styles */
@media print {
  .header,
  .footer,
  .controls,
  .btn,
  .mobile-menu-btn {
    display: none !important;
  }

  .hero {
    background: none !important;
    color: black !important;
  }

  .hero-title {
    color: black !important;
    -webkit-text-fill-color: black !important;
  }

  .section,
  .theory-card,
  .demo-card,
  .applications-card,
  .example-card {
    background: white !important;
    box-shadow: none !important;
    border: 1px solid #ccc !important;
  }

  .visualization-container {
    border: 2px solid #000 !important;
    background: white !important;
  }

  .page-break {
    page-break-before: always;
  }
}

/* Focus styles for accessibility */
.btn:focus,
input:focus,
textarea:focus {
  outline: 3px solid var(--scheme-brand-600-50);
  outline-offset: 2px;
}

/* Screen reader only content */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* Loading states */
.btn.loading {
  position: relative;
  pointer-events: none;
}

.btn.loading::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 16px;
  height: 16px;
  margin: -8px 0 0 -8px;
  border: 2px solid transparent;
  border-top-color: currentColor;
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

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

/* Dark mode support (if needed in future) */
@media (prefers-color-scheme: dark) {
  /* Uncomment and customize if dark mode is needed */
  /*
  :root {
    --scheme-neutral-1200: var(--scheme-neutral-100);
    --scheme-neutral-1100: var(--scheme-neutral-200);
    --scheme-neutral-1000: var(--scheme-neutral-300);
    --scheme-neutral-200: var(--scheme-neutral-1000);
    --scheme-neutral-300: var(--scheme-neutral-900);
    --scheme-neutral-400: var(--scheme-neutral-800);
  }

  body {
    background: linear-gradient(135deg, var(--scheme-neutral-100) 0%, var(--scheme-accent-200) 100%);
  }
  */
}

/* Utility classes */
.text-center {
  text-align: center;
}

.text-left {
  text-align: left;
}

.text-right {
  text-align: right;
}

.mt-0 { margin-top: 0; }
.mt-1 { margin-top: var(--spacing-xs); }
.mt-2 { margin-top: var(--spacing-sm); }
.mt-3 { margin-top: var(--spacing-md); }
.mt-4 { margin-top: var(--spacing-lg); }
.mt-5 { margin-top: var(--spacing-xl); }

.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: var(--spacing-xs); }
.mb-2 { margin-bottom: var(--spacing-sm); }
.mb-3 { margin-bottom: var(--spacing-md); }
.mb-4 { margin-bottom: var(--spacing-lg); }
.mb-5 { margin-bottom: var(--spacing-xl); }

.hidden {
  display: none;
}

.visible {
  display: block;
}

.flex {
  display: flex;
}

.items-center {
  align-items: center;
}

.justify-center {
  justify-content: center;
}

.gap-1 { gap: var(--spacing-xs); }
.gap-2 { gap: var(--spacing-sm); }
.gap-3 { gap: var(--spacing-md); }
.gap-4 { gap: var(--spacing-lg); }

/* Smooth scrolling for anchor links */
html {
  scroll-behavior: smooth;
}

/* Enhanced focus indicators */
*:focus-visible {
  outline: 2px solid var(--scheme-brand-500);
  outline-offset: 2px;
}
.logo-link {
  display: flex;
  align-items: center;
  gap: 8px;
  color: inherit;
  text-decoration: none;
  transition: transform 0.2s ease;
}

.logo-link:hover {
  transform: scale(1.05);
  color: #007bff; /* ví dụ xanh xanh */
}