/* Enhanced Features CSS */

/* ==========================================
   CSS Custom Properties for Font Size
   ========================================== */
:root {
  --base-font-size: 16px;
}

body {
  font-size: var(--base-font-size);
}

/* ==========================================
   Dark Mode
   ========================================== */
.dark-mode {
  --primary: #60A5FA;
  --primary-dark: #3B82F6;
  --primary-light: #1E3A5F;
  --secondary: #34D399;
  --secondary-light: #064E3B;
  --accent: #A78BFA;
  --accent-light: #312E81;
  --background: #0F172A;
  --surface: #1E293B;
  --text-primary: #F1F5F9;
  --text-secondary: #94A3B8;
  --text-muted: #64748B;
  --border: #334155;
  --border-light: #1E293B;
  --success: #34D399;
  --warning: #FBBF24;
  --error: #F87171;
}

.dark-mode .header {
  background: var(--surface);
  border-color: var(--border);
}

.dark-mode .sidebar {
  background: var(--surface);
  border-color: var(--border);
}

.dark-mode .card {
  background: var(--surface);
  border-color: var(--border);
}

.dark-mode .card:hover {
  border-color: var(--primary);
}

.dark-mode .hero {
  background: linear-gradient(135deg, #1E40AF 0%, #5B21B6 100%);
}

/* Dark mode: Code blocks with lighter background for contrast */
.dark-mode .content pre {
  background: #F1F5F9;
}

.dark-mode .content pre code {
  background: transparent !important;
  color: #1E293B;
}

.dark-mode .content pre .copy-code-btn {
  background: rgba(0, 0, 0, 0.1);
  color: #64748B;
}

.dark-mode .content pre:hover .copy-code-btn {
  opacity: 1;
}

.dark-mode .content pre .copy-code-btn:hover {
  background: rgba(0, 0, 0, 0.2);
  color: #1E293B;
}

/* Dark mode syntax highlighting for light background */
.dark-mode .hljs {
  background: #F1F5F9 !important;
  color: #1E293B !important;
}

.dark-mode .hljs-keyword { color: #7C3AED; }
.dark-mode .hljs-string { color: #059669; }
.dark-mode .hljs-number { color: #D97706; }
.dark-mode .hljs-function { color: #2563EB; }
.dark-mode .hljs-comment { color: #64748B; font-style: italic; }
.dark-mode .hljs-built_in { color: #DB2777; }
.dark-mode .hljs-params { color: #BE185D; }
.dark-mode .hljs-title { color: #2563EB; }
.dark-mode .hljs-title.function_ { color: #2563EB; }
.dark-mode .hljs-title.class_ { color: #DB2777; }
.dark-mode .hljs-attr { color: #BE185D; }
.dark-mode .hljs-variable { color: #1E293B; }
.dark-mode .hljs-literal { color: #D97706; }
.dark-mode .hljs-operator { color: #475569; }
.dark-mode .hljs-punctuation { color: #475569; }
.dark-mode .hljs-meta { color: #64748B; }
.dark-mode .hljs-decorator { color: #D97706; }
.dark-mode .hljs-subst { color: #1E293B; }

/* Dark mode: Inline code */
.dark-mode .content code {
  background: #E2E8F0;
  color: #7C3AED;
}

/* Dark mode: Python playground with lighter background */
.dark-mode .python-playground {
  border-color: #475569;
}

.dark-mode .playground-editor {
  background: #F1F5F9;
}

.dark-mode .playground-editor pre {
  background: #F1F5F9 !important;
}

.dark-mode .playground-editor pre code {
  color: #1E293B;
}

.dark-mode .playground-editor textarea {
  caret-color: #1E293B;
}

.dark-mode .playground-editor textarea::selection {
  background: rgba(37, 99, 235, 0.3);
}

.dark-mode .line-numbers {
  background: #F1F5F9;
  border-right-color: #CBD5E1;
  color: #94A3B8;
}

.dark-mode .playground-output {
  background: #F8FAFC;
  border-top-color: #CBD5E1;
}

.dark-mode .playground-output-header {
  background: rgba(0, 0, 0, 0.05);
  color: #64748B;
}

.dark-mode .playground-output-content {
  color: #1E293B;
}

.dark-mode .playground-output-content.success {
  color: #059669;
}

.dark-mode .playground-output-content.error {
  color: #DC2626;
}

.dark-mode .running-indicator {
  color: #1E293B;
}

.dark-mode .running-indicator .running-spinner circle {
  stroke: #1E293B;
}

.dark-mode .execution-time {
  background: rgba(0, 0, 0, 0.1);
  color: #64748B;
}

.dark-mode .playground-editor .copy-code-btn {
  background: rgba(0, 0, 0, 0.1);
  color: #64748B;
}

.dark-mode .playground-editor .copy-code-btn:hover {
  background: rgba(0, 0, 0, 0.2);
  color: #1E293B;
}

.dark-mode .lesson-nav-btn {
  background: var(--surface);
  border-color: var(--border);
}

.dark-mode .lesson-meta {
  background: var(--border-light);
}

.dark-mode .sidebar-item-number {
  background: var(--border);
}

.dark-mode .checklist li::before {
  border-color: var(--border);
}

/* Dark mode icon toggle */
#dark-mode-toggle .sun-icon {
  display: block;
}

#dark-mode-toggle .moon-icon {
  display: none;
}

.dark-mode #dark-mode-toggle .sun-icon {
  display: none;
}

.dark-mode #dark-mode-toggle .moon-icon {
  display: block;
}

/* ==========================================
   Toolbar (Dark mode, Font size, Search)
   ========================================== */
.toolbar {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-left: auto;
}

.toolbar-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition);
}

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

.toolbar-btn:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.toolbar-btn svg {
  width: 18px;
  height: 18px;
}

.font-size-control {
  display: flex;
  align-items: center;
  gap: 4px;
  padding: 4px;
  border: 1px solid var(--border);
  border-radius: 8px;
}

.font-size-control button {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  background: transparent;
  border: none;
  border-radius: 4px;
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 1rem;
  font-weight: bold;
}

.font-size-control button:hover {
  background: var(--border-light);
  color: var(--text-primary);
}

.font-size-control span {
  min-width: 40px;
  text-align: center;
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* ==========================================
   Breadcrumb Navigation
   ========================================== */
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
  font-size: 0.875rem;
  color: var(--text-muted);
}

.breadcrumb a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition);
}

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

.breadcrumb-sep {
  color: var(--border);
}

/* ==========================================
   Lesson Meta Bar
   ========================================== */
.lesson-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 16px;
  margin-bottom: 24px;
  padding: 12px 16px;
  background: var(--border-light);
  border-radius: 8px;
}

.lesson-meta-item {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.lesson-meta-item svg {
  width: 16px;
  height: 16px;
  color: var(--text-muted);
}

.bookmark-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-left: auto;
  padding: 6px 12px;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.8125rem;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition);
}

.bookmark-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.bookmark-btn.active {
  background: var(--primary-light);
  border-color: var(--primary);
  color: var(--primary);
}

.bookmark-btn svg {
  width: 16px;
  height: 16px;
}

/* ==========================================
   Jump to Exercises
   ========================================== */
.jump-to-exercises {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  background: var(--accent-light);
  border-radius: 8px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--accent);
  text-decoration: none;
  transition: all var(--transition);
  margin-bottom: 24px;
}

.jump-to-exercises:hover {
  background: var(--accent);
  color: white;
}

.jump-to-exercises svg {
  width: 16px;
  height: 16px;
}

/* ==========================================
   Search Modal
   ========================================== */
.search-modal-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(4px);
  z-index: 200;
  align-items: flex-start;
  justify-content: center;
  padding-top: 15vh;
}

.search-modal-overlay.open {
  display: flex;
}

.search-modal {
  width: 100%;
  max-width: 560px;
  background: var(--surface);
  border-radius: 12px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
  overflow: hidden;
  animation: slideDown 0.2s ease;
}

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

.search-input-wrapper {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px 20px;
  border-bottom: 1px solid var(--border);
}

.search-input-wrapper svg {
  width: 20px;
  height: 20px;
  color: var(--text-muted);
  flex-shrink: 0;
}

.search-input-wrapper input {
  flex: 1;
  border: none;
  background: transparent;
  font-size: 1rem;
  color: var(--text-primary);
  outline: none;
}

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

.search-shortcut {
  padding: 4px 8px;
  background: var(--border-light);
  border-radius: 4px;
  font-size: 0.75rem;
  color: var(--text-muted);
}

.search-results {
  max-height: 400px;
  overflow-y: auto;
  padding: 8px;
}

.search-hint,
.search-no-results {
  padding: 24px;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.875rem;
}

.search-result {
  padding: 12px 16px;
  border-radius: 8px;
  cursor: pointer;
  transition: background var(--transition);
}

.search-result:hover {
  background: var(--border-light);
}

.search-result-title {
  font-weight: 500;
  color: var(--text-primary);
  margin-bottom: 4px;
}

.search-result-snippet {
  font-size: 0.8125rem;
  color: var(--text-muted);
  line-height: 1.5;
}

/* ==========================================
   Copy Code Button
   ========================================== */
.copy-code-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  display: flex;
  align-items: center;
  gap: 4px;
  padding: 4px 8px;
  background: rgba(255, 255, 255, 0.1);
  border: none;
  border-radius: 4px;
  font-size: 0.75rem;
  color: #94A3B8;
  cursor: pointer;
  opacity: 0;
  transition: all var(--transition);
  z-index: 10;
}

pre:hover .copy-code-btn,
.playground-editor:hover .copy-code-btn {
  opacity: 1;
}

.copy-code-btn:hover {
  background: rgba(255, 255, 255, 0.2);
  color: #E2E8F0;
}

.copy-code-btn.copied {
  background: var(--success);
  color: white;
}

/* ==========================================
   Line Numbers for Code Editor
   ========================================== */
.playground-editor-with-lines {
  display: flex;
}

.line-numbers {
  flex-shrink: 0;
  padding: 16px 0;
  padding-right: 12px;
  background: #1E293B;
  border-right: 1px solid #334155;
  text-align: right;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.875rem;
  line-height: 1.6;
  color: #475569;
  user-select: none;
  pointer-events: none;
}

.line-numbers span {
  display: block;
  padding: 0 12px;
}

/* ==========================================
   Execution Time Display
   ========================================== */
.execution-time {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px 8px;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 4px;
  font-size: 0.75rem;
  color: #94A3B8;
  margin-left: auto;
}

.execution-time svg {
  width: 12px;
  height: 12px;
}

/* ==========================================
   Skeleton Loading
   ========================================== */
.skeleton-loader {
  padding: 20px 0;
}

.skeleton {
  background: linear-gradient(90deg, var(--border-light) 25%, var(--border) 50%, var(--border-light) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: 4px;
  margin-bottom: 16px;
}

.skeleton-breadcrumb {
  width: 200px;
  height: 16px;
}

.skeleton-title {
  width: 60%;
  height: 36px;
  margin-bottom: 24px;
}

.skeleton-meta {
  width: 300px;
  height: 44px;
  border-radius: 8px;
  margin-bottom: 24px;
}

.skeleton-text {
  width: 100%;
  height: 16px;
}

.skeleton-text.short {
  width: 70%;
}

.skeleton-code {
  width: 100%;
  height: 120px;
  border-radius: 8px;
  margin: 24px 0;
}

@keyframes shimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}

/* ==========================================
   Skip to Main Content (Accessibility)
   ========================================== */
.skip-link {
  position: absolute;
  top: -100px;
  left: 50%;
  transform: translateX(-50%);
  padding: 12px 24px;
  background: var(--primary);
  color: white;
  font-weight: 600;
  border-radius: 0 0 8px 8px;
  z-index: 1000;
  text-decoration: none;
  transition: top 0.2s;
}

.skip-link:focus {
  top: 0;
}

/* ==========================================
   Screen Reader Only (Accessibility)
   ========================================== */
.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;
}

/* ==========================================
   Improved Focus Indicators
   ========================================== */
*:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.sidebar-item:focus-visible {
  outline-offset: -2px;
  background: var(--primary-light);
}

.card:focus-visible {
  outline-offset: 0;
  box-shadow: 0 0 0 3px var(--primary-light);
}

button:focus-visible,
a:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

/* ==========================================
   Sidebar Tooltip Preview
   ========================================== */
.sidebar-item {
  position: relative;
}

.sidebar-item[title]:hover::after {
  content: attr(title);
  position: absolute;
  left: 100%;
  top: 50%;
  transform: translateY(-50%);
  margin-left: 12px;
  padding: 8px 12px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.75rem;
  color: var(--text-secondary);
  white-space: pre-line;
  max-width: 200px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  z-index: 100;
  pointer-events: none;
}

@media (max-width: 1024px) {
  .sidebar-item[title]:hover::after {
    display: none;
  }
}

/* ==========================================
   Auto-save Indicator
   ========================================== */
.auto-save-indicator {
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 0.75rem;
  color: var(--text-muted);
  padding: 4px 8px;
}

.auto-save-indicator.saved {
  color: var(--success);
}

.auto-save-indicator svg {
  width: 12px;
  height: 12px;
}

/* ==========================================
   Responsive Adjustments
   ========================================== */
@media (max-width: 640px) {
  .toolbar {
    gap: 4px;
  }

  .toolbar-btn {
    width: 32px;
    height: 32px;
  }

  .font-size-control {
    display: none;
  }

  .search-modal {
    margin: 16px;
    max-width: calc(100% - 32px);
  }

  .lesson-meta {
    flex-direction: column;
    align-items: flex-start;
    gap: 8px;
  }

  .bookmark-btn {
    margin-left: 0;
  }

  .breadcrumb {
    flex-wrap: wrap;
    font-size: 0.75rem;
  }
}