/* Modern CSS Variables for Theming */
:root {
  /* Color Palette */
  --primary-color: #6366f1;
  --primary-hover: #5855eb;
  --secondary-color: #8b5cf6;
  --accent-color: #06b6d4;
  
  /* Background Colors */
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-tertiary: #334155;
  --bg-card: #1e293b;
  --bg-hover: #334155;
  
  /* Text Colors */
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --text-accent: #38bdf8;
  
  /* Border Colors */
  --border-primary: #334155;
  --border-secondary: #475569;
  --border-hover: #64748b;
  
  /* Status Colors */
  --success-color: #10b981;
  --error-color: #ef4444;
  --warning-color: #f59e0b;
  --info-color: #3b82f6;
  
  /* Difficulty Colors */
  --easy-color: #22c55e;
  --medium-color: #f59e0b;
  --hard-color: #ef4444;
  --expert-color: #8b5cf6;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
  
  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  
  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 0.75rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  
  /* Typography */
  --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;
  
  /* Transitions */
  --transition-fast: 150ms ease-in-out;
  --transition-base: 250ms ease-in-out;
  --transition-slow: 350ms ease-in-out;
}

/* Light Theme */
[data-theme="light"] {
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-tertiary: #e2e8f0;
  --bg-card: #ffffff;
  --bg-hover: #f1f5f9;
  
  --text-primary: #0f172a;
  --text-secondary: #334155;
  --text-muted: #64748b;
  --text-accent: #0ea5e9;
  
  --border-primary: #e2e8f0;
  --border-secondary: #cbd5e1;
  --border-hover: #94a3b8;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  font-size: var(--font-size-base);
  line-height: 1.6;
  overflow-x: hidden;
}

/* Scrollbar Styling */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}

::-webkit-scrollbar-thumb {
  background: var(--border-secondary);
  border-radius: var(--radius-md);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--border-hover);
}

/* Navigation */
.navbar {
  background: var(--bg-card);
  border-bottom: 1px solid var(--border-primary);
  padding: 0 var(--spacing-lg);
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  backdrop-filter: blur(10px);
}

.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 1400px;
  margin: 0 auto;
  height: 64px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--primary-color);
}

.nav-brand i {
  font-size: 1.5rem;
}

.nav-menu {
  display: flex;
  gap: var(--spacing-sm);
}

.nav-btn {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-sm) var(--spacing-md);
  background: transparent;
  border: none;
  color: var(--text-secondary);
  border-radius: var(--radius-md);
  font-size: var(--font-size-sm);
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.nav-btn:hover {
  background: var(--bg-hover);
  color: var(--text-primary);
}

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

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

.theme-toggle, .user-profile {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  background: var(--bg-hover);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all var(--transition-fast);
  color: var(--text-secondary);
}

.theme-toggle:hover, .user-profile:hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

/* Main Content */
.main-content {
  padding-top: 64px;
  min-height: 100vh;
}

.content-section {
  display: none;
  animation: fadeIn 0.3s ease-in-out;
}

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

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

/* Section Headers */
.section-header {
  padding: var(--spacing-xl) var(--spacing-lg);
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-primary);
}

.section-header h1 {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  margin-bottom: var(--spacing-lg);
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.filter-controls {
  display: flex;
  gap: var(--spacing-md);
  flex-wrap: wrap;
}

.filter-select, .search-input {
  padding: var(--spacing-sm) var(--spacing-md);
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: var(--font-size-sm);
  transition: all var(--transition-fast);
}

.filter-select:focus, .search-input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.search-input {
  min-width: 250px;
  flex: 1;
}

.search-input::placeholder {
  color: var(--text-muted);
}

/* No Problems Message */
.no-problems {
  grid-column: 1 / -1;
  text-align: center;
  padding: var(--spacing-2xl);
  color: var(--text-muted);
  font-size: var(--font-size-lg);
}

/* Problems Grid */
.problems-grid {
  padding: var(--spacing-xl) var(--spacing-lg);
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
  gap: var(--spacing-lg);
  max-width: 1400px;
  margin: 0 auto;
}

.problem-card {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  cursor: pointer;
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}

.problem-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
  transform: scaleX(0);
  transition: transform var(--transition-base);
}

.problem-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  border-color: var(--border-hover);
}

.problem-card:hover::before {
  transform: scaleX(1);
}

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

.problem-title {
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--spacing-xs);
}

.problem-meta {
  display: flex;
  gap: var(--spacing-sm);
  align-items: center;
}

.difficulty-badge {
  padding: 4px 8px;
  border-radius: var(--radius-sm);
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.difficulty-badge.easy {
  background: rgba(34, 197, 94, 0.1);
  color: var(--easy-color);
  border: 1px solid rgba(34, 197, 94, 0.2);
}

.difficulty-badge.medium {
  background: rgba(245, 158, 11, 0.1);
  color: var(--medium-color);
  border: 1px solid rgba(245, 158, 11, 0.2);
}

.difficulty-badge.hard {
  background: rgba(239, 68, 68, 0.1);
  color: var(--hard-color);
  border: 1px solid rgba(239, 68, 68, 0.2);
}

.difficulty-badge.expert {
  background: rgba(139, 92, 246, 0.1);
  color: var(--expert-color);
  border: 1px solid rgba(139, 92, 246, 0.2);
}

.category-badge {
  padding: 4px 8px;
  background: var(--bg-tertiary);
  color: var(--text-secondary);
  border-radius: var(--radius-sm);
  font-size: var(--font-size-xs);
  font-weight: 500;
}

.problem-description {
  color: var(--text-secondary);
  font-size: var(--font-size-sm);
  line-height: 1.6;
  margin-bottom: var(--spacing-md);
}

.problem-stats {
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: var(--text-muted);
  font-size: var(--font-size-sm);
}

.problem-solved {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  color: var(--success-color);
}

/* Problem Detail & Compiler */
.problem-workspace {
  display: grid;
  grid-template-columns: 1fr 1fr;
  height: calc(100vh - 64px);
}

.problem-panel {
  background: var(--bg-secondary);
  border-right: 1px solid var(--border-primary);
  overflow-y: auto;
}

.problem-header {
  padding: var(--spacing-lg);
  border-bottom: 1px solid var(--border-primary);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.back-btn {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-sm) var(--spacing-md);
  background: var(--bg-hover);
  border: none;
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.back-btn:hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

.problem-meta {
  display: flex;
  gap: var(--spacing-sm);
}

.problem-difficulty, .problem-category {
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-sm);
  font-size: var(--font-size-xs);
  font-weight: 600;
}

.problem-content {
  padding: var(--spacing-lg);
}

.problem-content h2 {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  margin-bottom: var(--spacing-lg);
  color: var(--text-primary);
}

.problem-description p {
  margin-bottom: var(--spacing-md);
  line-height: 1.7;
  color: var(--text-secondary);
}

.problem-examples, .problem-constraints {
  margin-top: var(--spacing-xl);
}

.problem-examples h3, .problem-constraints h3 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
}

.example {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
  margin-bottom: var(--spacing-md);
}

.example h4 {
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
  color: var(--text-accent);
}

.example pre {
  background: var(--bg-primary);
  padding: var(--spacing-sm);
  border-radius: var(--radius-sm);
  font-family: 'JetBrains Mono', monospace;
  font-size: var(--font-size-sm);
  overflow-x: auto;
  color: var(--text-primary);
}

/* Code Panel */
.code-panel {
  display: flex;
  flex-direction: column;
  background: var(--bg-primary);
}

.code-editor-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-md) var(--spacing-lg);
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-primary);
}

.editor-tabs {
  display: flex;
  gap: var(--spacing-sm);
}

.tab-btn {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-sm) var(--spacing-md);
  background: transparent;
  border: none;
  color: var(--text-secondary);
  border-radius: var(--radius-md);
  font-size: var(--font-size-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
}

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

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

.editor-actions {
  display: flex;
  gap: var(--spacing-sm);
}

.action-btn {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-sm) var(--spacing-md);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-md);
  background: var(--bg-card);
  color: var(--text-secondary);
  font-size: var(--font-size-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.action-btn:hover {
  background: var(--bg-hover);
  color: var(--text-primary);
  border-color: var(--border-hover);
}

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

.action-btn.primary:hover {
  background: var(--primary-hover);
}

.code-editor-container {
  flex: 1;
  position: relative;
}

.tab-content {
  display: none;
  height: 100%;
}

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

.code-editor {
  width: 100%;
  height: 400px;
  background: var(--bg-primary);
  color: var(--text-primary);
  border: none;
  padding: var(--spacing-lg);
  font-family: 'JetBrains Mono', monospace;
  font-size: 14px;
  line-height: 1.6;
  resize: none;
  outline: none;
  tab-size: 2;
}

.code-editor::placeholder {
  color: var(--text-muted);
}

.test-cases {
  padding: var(--spacing-lg);
  height: 400px;
  overflow-y: auto;
}

.test-case {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
  margin-bottom: var(--spacing-md);
}

.test-case h4 {
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
}

.test-case pre {
  background: var(--bg-secondary);
  padding: var(--spacing-sm);
  border-radius: var(--radius-sm);
  font-family: 'JetBrains Mono', monospace;
  font-size: var(--font-size-sm);
  margin-bottom: var(--spacing-xs);
  overflow-x: auto;
}

/* Output Panel */
.output-panel {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-primary);
  height: 250px;
  display: flex;
  flex-direction: column;
}

.output-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-md) var(--spacing-lg);
  border-bottom: 1px solid var(--border-primary);
}

.output-header h3 {
  font-size: var(--font-size-lg);
  font-weight: 600;
}

.output-status {
  padding: 4px 8px;
  border-radius: var(--radius-sm);
  font-size: var(--font-size-xs);
  font-weight: 600;
}

.output-status.ready {
  background: rgba(156, 163, 175, 0.1);
  color: var(--text-muted);
}

.output-status.running {
  background: rgba(59, 130, 246, 0.1);
  color: var(--info-color);
}

.output-status.success {
  background: rgba(16, 185, 129, 0.1);
  color: var(--success-color);
}

.output-status.error {
  background: rgba(239, 68, 68, 0.1);
  color: var(--error-color);
}

.output-content {
  flex: 1;
  padding: var(--spacing-lg);
  overflow-y: auto;
  font-family: 'JetBrains Mono', monospace;
  font-size: var(--font-size-sm);
  line-height: 1.6;
}

.output-placeholder {
  color: var(--text-muted);
  text-align: center;
  padding: var(--spacing-xl) 0;
}

.output-success {
  color: var(--success-color);
}

.output-error {
  color: var(--error-color);
}

/* Compiler Section */
.compiler-workspace {
  max-width: 1400px;
  margin: 0 auto;
  padding: var(--spacing-xl) var(--spacing-lg);
}

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

.compiler-header h2 {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.compiler-actions {
  display: flex;
  gap: var(--spacing-sm);
}

.compiler-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-xl);
  height: calc(100vh - 200px);
}

.compiler-editor {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.compiler-editor .code-editor {
  height: 100%;
  border-radius: var(--radius-lg);
}

.compiler-output {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  display: flex;
  flex-direction: column;
}

/* Progress Dashboard */
.progress-dashboard {
  max-width: 1400px;
  margin: 0 auto;
  padding: var(--spacing-xl) var(--spacing-lg);
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-2xl);
}

.stat-card {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  display: flex;
  align-items: center;
  gap: var(--spacing-lg);
  transition: all var(--transition-base);
}

.stat-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.stat-icon {
  width: 60px;
  height: 60px;
  border-radius: var(--radius-xl);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
}

.stat-icon.easy {
  background: rgba(34, 197, 94, 0.1);
  color: var(--easy-color);
}

.stat-icon.medium {
  background: rgba(245, 158, 11, 0.1);
  color: var(--medium-color);
}

.stat-icon.hard {
  background: rgba(239, 68, 68, 0.1);
  color: var(--hard-color);
}

.stat-icon.expert {
  background: rgba(139, 92, 246, 0.1);
  color: var(--expert-color);
}

.stat-content h3 {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  margin-bottom: var(--spacing-xs);
}

.stat-content p {
  color: var(--text-secondary);
  font-weight: 500;
}

.progress-charts {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
}

.progress-charts h3 {
  font-size: var(--font-size-xl);
  font-weight: 600;
  margin-bottom: var(--spacing-xl);
}

.category-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--spacing-lg);
}

.category-name {
  font-weight: 500;
  min-width: 150px;
}

.progress-bar {
  flex: 1;
  height: 8px;
  background: var(--bg-secondary);
  border-radius: var(--radius-sm);
  margin: 0 var(--spacing-md);
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
  border-radius: var(--radius-sm);
  transition: width var(--transition-slow);
}

.progress-text {
  color: var(--text-muted);
  font-size: var(--font-size-sm);
  min-width: 50px;
  text-align: right;
}

/* Loading Overlay */
.loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(15, 23, 42, 0.8);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 9999;
  backdrop-filter: blur(5px);
}

.loading-overlay.active {
  display: flex;
}

.loading-spinner {
  text-align: center;
  color: var(--text-primary);
}

.spinner {
  width: 50px;
  height: 50px;
  border: 4px solid var(--border-primary);
  border-top: 4px solid var(--primary-color);
  border-radius: 50%;
  animation: spin 1s linear infinite;
  margin: 0 auto var(--spacing-md);
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

/* Modals */
.modal {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(15, 23, 42, 0.8);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 10000;
  backdrop-filter: blur(5px);
}

.modal.active {
  display: flex;
}

.modal-content {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-xl);
  padding: var(--spacing-2xl);
  text-align: center;
  max-width: 400px;
  width: 90%;
  animation: modalSlideIn 0.3s ease-out;
}

@keyframes modalSlideIn {
  from {
    opacity: 0;
    transform: translateY(-20px) scale(0.95);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

.modal-icon {
  font-size: 4rem;
  margin-bottom: var(--spacing-lg);
}

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

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

.modal-content h3 {
  font-size: var(--font-size-xl);
  font-weight: 600;
  margin-bottom: var(--spacing-md);
}

.modal-content p {
  color: var(--text-secondary);
  margin-bottom: var(--spacing-xl);
  line-height: 1.6;
}

.modal-btn {
  padding: var(--spacing-md) var(--spacing-xl);
  background: var(--primary-color);
  color: white;
  border: none;
  border-radius: var(--radius-md);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.modal-btn:hover {
  background: var(--primary-hover);
  transform: translateY(-1px);
}

/* Responsive Design */
@media (max-width: 1200px) {
  .problem-workspace {
    grid-template-columns: 1fr;
  }
  
  .compiler-content {
    grid-template-columns: 1fr;
    height: auto;
  }
  
  .compiler-editor .code-editor,
  .compiler-output {
    height: 400px;
  }
}

@media (max-width: 768px) {
  .nav-container {
    padding: 0 var(--spacing-md);
  }
  
  .nav-menu {
    display: none;
  }
  
  .problems-grid {
    grid-template-columns: 1fr;
    padding: var(--spacing-md);
  }
  
  .filter-controls {
    flex-direction: column;
  }
  
  .search-input {
    min-width: auto;
  }
  
  .section-header {
    padding: var(--spacing-md);
  }
  
  .section-header h1 {
    font-size: var(--font-size-2xl);
  }
  
  .problem-header {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--spacing-md);
  }
  
  .editor-actions {
    flex-wrap: wrap;
  }
  
  .stats-grid {
    grid-template-columns: 1fr;
  }
  
  .category-item {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--spacing-sm);
  }
  
  .progress-bar {
    margin: 0;
    width: 100%;
  }
}

@media (max-width: 480px) {
  .modal-content {
    margin: var(--spacing-md);
    padding: var(--spacing-lg);
  }
  
  .problem-card {
    padding: var(--spacing-md);
  }
  
  .code-editor {
    font-size: 12px;
  }
}

/* Animation Classes */
.fade-in {
  animation: fadeIn 0.3s ease-in-out;
}

.slide-up {
  animation: slideUp 0.3s ease-out;
}

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

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

.text-success {
  color: var(--success-color);
}

.text-error {
  color: var(--error-color);
}

.text-warning {
  color: var(--warning-color);
}

.text-info {
  color: var(--info-color);
}

.hidden {
  display: none !important;
}

.visible {
  display: block !important;
}

/* Focus States */
button:focus-visible,
.nav-btn:focus-visible,
.action-btn:focus-visible {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

/* Selection */
::selection {
  background: rgba(99, 102, 241, 0.3);
  color: var(--text-primary);
}