/* Neural Slate & Cyber Violet Design System */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=JetBrains+Mono:ital,wght@0,400;0,600;1,400&family=Plus+Jakarta+Sans:wght@500;600;700;800&display=swap');

:root {
  /* Color Tokens */
  --bg-dark: #0B0F19;
  --bg-surface: #111827;
  --bg-surface-elevated: #1F2937;
  --bg-glass: rgba(17, 24, 39, 0.75);
  --border-color: rgba(255, 255, 255, 0.08);
  --border-glow: rgba(99, 102, 241, 0.3);
  
  --primary-accent: #6366F1;
  --primary-glow: rgba(99, 102, 241, 0.4);
  --secondary-accent: #06B6D4;
  --success-accent: #10B981;
  --warning-accent: #F59E0B;
  
  --text-main: #F9FAFB;
  --text-muted: #9CA3AF;
  --text-dim: #6B7280;
  
  /* Illustration SVG tokens (used by assets/ SVG diagrams) */
  --t: #E5E7EB;
  --surface-0: #0B0F19;
  --surface-1: #111827;
  --border-strong: rgba(255, 255, 255, 0.18);
  --text-secondary: #9CA3AF;
  --text-warning: #F59E0B;
  
  /* Typography */
  --font-display: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Plus Jakarta Sans', 'Segoe UI', Roboto, sans-serif;
  --font-body: -apple-system, BlinkMacSystemFont, 'SF Pro Text', 'Inter', 'Segoe UI', Roboto, sans-serif;
  --font-code: 'JetBrains Mono', monospace;
  
  /* Geometry */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-full: 9999px;
  
  --sidebar-width: 320px;
  --transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --shadow-glow: 0 0 25px rgba(99, 102, 241, 0.15);
}

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

html, body {
  height: 100%;
  background-color: var(--bg-dark);
  color: var(--text-main);
  font-family: var(--font-body);
  font-size: 15px;
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

/* Accessible focus rings (Apple-style) */
:focus-visible, button:focus-visible, input:focus-visible, select:focus-visible, textarea:focus-visible, [role="button"]:focus-visible {
  outline: 2px solid var(--primary-accent) !important;
  outline-offset: 2px !important;
}

/* Custom Scrollbar */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}
::-webkit-scrollbar-track {
  background: var(--bg-dark);
}
::-webkit-scrollbar-thumb {
  background: var(--bg-surface-elevated);
  border-radius: var(--radius-full);
}
::-webkit-scrollbar-thumb:hover {
  background: var(--primary-accent);
}

/* Typography Hierarchy */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 700;
  color: var(--text-main);
  line-height: 1.25;
  letter-spacing: -0.02em;
}

/* App Layout Grid */
.app-container {
  display: flex;
  min-height: 100vh;
  position: relative;
}

/* Header / Navigation Bar */
.top-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 64px;
  background: var(--bg-glass);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-color);
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.15rem;
  color: #FFF;
  text-decoration: none;
}

.brand-badge {
  background: linear-gradient(135deg, var(--primary-accent), var(--secondary-accent));
  color: #FFF;
  padding: 0.25rem 0.6rem;
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.5px;
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.search-trigger-btn {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  padding: 0.45rem 0.9rem;
  border-radius: var(--radius-md);
  font-size: 0.85rem;
  cursor: pointer;
  transition: var(--transition-fast);
}

.search-trigger-btn:hover {
  border-color: var(--primary-accent);
  color: var(--text-main);
  box-shadow: 0 0 12px var(--primary-glow);
}

.kbd-shortcut {
  background: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 0.1rem 0.4rem;
  font-size: 0.7rem;
  font-family: var(--font-code);
}

/* Sidebar Component */
.sidebar {
  width: var(--sidebar-width);
  background: var(--bg-surface);
  border-right: 1px solid var(--border-color);
  position: fixed;
  top: 64px;
  bottom: 0;
  left: 0;
  overflow-y: auto;
  padding: 1.25rem 1rem;
  transition: transform var(--transition-fast);
  z-index: 90;
}

.sidebar-title {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-dim);
  margin-bottom: 1rem;
  padding-left: 0.5rem;
}

.stage-nav-item {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  padding: 0.75rem 0.85rem;
  border-radius: var(--radius-md);
  color: var(--text-muted);
  text-decoration: none;
  cursor: pointer;
  margin-bottom: 0.35rem;
  transition: var(--transition-fast);
  border: 1px solid transparent;
}

.stage-nav-item:hover {
  background: rgba(255, 255, 255, 0.03);
  color: var(--text-main);
}

.stage-nav-item.active {
  background: rgba(99, 102, 241, 0.12);
  color: #FFF;
  border-color: var(--border-glow);
  box-shadow: var(--shadow-glow);
}

.stage-num-badge {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--bg-surface-elevated);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--primary-accent);
}

.stage-nav-item.active .stage-num-badge {
  background: var(--primary-accent);
  color: #FFF;
}

.stage-nav-info {
  display: flex;
  flex-direction: column;
}

.stage-nav-name {
  font-weight: 600;
  font-size: 0.9rem;
}

.stage-nav-progress {
  font-size: 0.75rem;
  color: var(--text-dim);
}

/* Main Content Area */
.main-viewport {
  margin-left: var(--sidebar-width);
  margin-top: 64px;
  flex: 1;
  padding: 2.5rem 3rem 5rem 3rem;
  max-width: 1200px;
  overflow-x: hidden;
}

/* Stage Hero Header */
.stage-hero {
  background: linear-gradient(135deg, rgba(31, 41, 55, 0.6), rgba(17, 24, 39, 0.8));
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2rem 2.5rem;
  margin-bottom: 2.5rem;
  position: relative;
  overflow: hidden;
  overflow-wrap: break-word;
  word-break: break-word;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.25);
}

.stage-hero::after {
  content: '';
  position: absolute;
  top: -50%;
  right: -20%;
  width: 300px;
  height: 300px;
  background: radial-gradient(circle, var(--primary-glow) 0%, transparent 70%);
  pointer-events: none;
}

.stage-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: rgba(99, 102, 241, 0.15);
  color: var(--primary-accent);
  border: 1px solid var(--border-glow);
  padding: 0.3rem 0.8rem;
  border-radius: var(--radius-full);
  font-size: 0.8rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
}

.stage-title {
  font-size: 2.2rem;
  margin-bottom: 0.5rem;
  overflow-wrap: break-word;
  word-break: break-word;
}

.stage-subtitle {
  color: var(--text-muted);
  font-size: 1.05rem;
  max-width: 750px;
  overflow-wrap: break-word;
  word-break: break-word;
}

/* Module & Lesson Content Styles */
.module-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2rem;
  margin-bottom: 2rem;
  transition: transform var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.module-card:hover {
  transform: translateY(-2px);
  border-color: var(--border-glow);
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.18);
}

.module-title {
  font-size: 1.4rem;
  color: var(--secondary-accent);
  margin-bottom: 1.5rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.module-title-icon {
  width: 49px;
  height: 49px;
  flex: none;
  object-fit: contain;
  border-radius: 12px;
  border: 1px solid var(--border-color);
  background: var(--bg-surface-elevated);
  padding: 5px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.2);
}

body.light-theme .module-title-icon {
  background: #fff;
  box-shadow: 0 1px 3px rgba(16, 24, 40, 0.12);
}

.lesson-block {
  margin-bottom: 2rem;
}

.lesson-block:last-child {
  margin-bottom: 0;
}

.lesson-title {
  font-size: 1.15rem;
  color: var(--text-main);
  margin-bottom: 0.75rem;
}

.lesson-body {
  color: var(--text-muted);
  font-size: 0.98rem;
  line-height: 1.7;
  overflow-wrap: break-word;
  word-break: break-word;
}

.lesson-body p {
  margin-bottom: 1rem;
}

.lesson-body ul {
  list-style-type: none;
  padding-left: 1.25rem;
  margin-bottom: 1.25rem;
}

.lesson-body ul li {
  position: relative;
  margin-bottom: 0.5rem;
  padding-left: 0.5rem;
}

.lesson-body ul li::before {
  content: "•";
  color: var(--secondary-accent);
  font-weight: bold;
  position: absolute;
  left: -0.85rem;
}

.lesson-body ol {
  padding-left: 1.5rem;
  margin-bottom: 1.25rem;
}

.lesson-body ol li {
  margin-bottom: 0.5rem;
  padding-left: 0.25rem;
}

.lesson-body ol li::marker {
  color: var(--secondary-accent);
  font-weight: bold;
}

.lesson-body a {
  color: var(--secondary-accent);
  text-decoration: none;
  font-weight: 500;
  border-bottom: 1px dashed rgba(6, 182, 212, 0.4);
  transition: var(--transition-fast);
}

.lesson-body a:hover {
  color: var(--primary-accent);
  border-bottom: 1px solid var(--primary-accent);
  box-shadow: 0 2px 0 rgba(99, 102, 241, 0.15);
}

/* Code Blocks & Styling */
pre {
  background: var(--bg-dark) !important;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  font-family: var(--font-code);
  font-size: 0.88rem;
  overflow-x: auto;
  margin: 1.25rem 0;
  position: relative;
}

code {
  font-family: var(--font-code);
  color: var(--secondary-accent);
  background: rgba(6, 182, 212, 0.1);
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  font-size: 0.88em;
}

pre code {
  color: var(--text-main);
  background: transparent;
  padding: 0;
}

/* Interactive Laboratory Container */
.interactive-lab {
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-glow);
  border-radius: var(--radius-lg);
  padding: 2rem;
  margin: 2.5rem 0;
  box-shadow: var(--shadow-glow);
}

.lab-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.25rem;
}

.lab-title {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 1.2rem;
  color: var(--text-main);
}

.lab-badge {
  background: linear-gradient(135deg, var(--warning-accent), var(--primary-accent));
  color: #FFF;
  font-size: 0.7rem;
  font-weight: 800;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-full);
  text-transform: uppercase;
}

.lab-desc {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 1.5rem;
  overflow-wrap: break-word;
  word-break: break-word;
}

/* Interactive Widget 1: Client-Server Network Simulator */
.network-sim-grid {
  display: grid;
  grid-template-columns: 1fr 120px 1fr;
  gap: 1rem;
  align-items: center;
  background: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
}

.sim-node {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  text-align: center;
}

.sim-pipe {
  position: relative;
  height: 4px;
  background: var(--bg-surface-elevated);
  border-radius: 2px;
}

.sim-packet {
  position: absolute;
  top: -6px;
  left: 0;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--secondary-accent);
  box-shadow: 0 0 10px var(--secondary-accent);
  transition: left 1s ease-in-out;
}

/* Interactive Widget 2: Live Code Sandbox */
.sandbox-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  height: 380px;
}

.sandbox-editor {
  background: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem;
  display: flex;
  flex-direction: column;
}

.sandbox-textarea {
  flex: 1;
  background: transparent;
  border: none;
  color: var(--text-main);
  font-family: var(--font-code);
  font-size: 0.85rem;
  resize: none;
  outline: none;
}

.sandbox-preview {
  background: #FFF;
  border-radius: var(--radius-md);
  overflow: hidden;
}

.sandbox-iframe {
  width: 100%;
  height: 100%;
  border: none;
}

/* Interactive Widget 3: Git Terminal Visualizer */
.git-visualizer-container {
  background: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  font-family: var(--font-code);
}

.git-terminal-input {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-top: 1rem;
  background: var(--bg-surface);
  padding: 0.6rem 0.9rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
}

.git-cmd-input {
  background: transparent;
  border: none;
  color: var(--success-accent);
  font-family: var(--font-code);
  font-size: 0.9rem;
  flex: 1;
  outline: none;
}

.git-graph-svg {
  width: 100%;
  height: 140px;
  background: rgba(0, 0, 0, 0.4);
  border-radius: var(--radius-sm);
}

/* Interactive Widget 4: API & Auth Inspector */
.api-inspector-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

.api-request-panel, .api-response-panel {
  background: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem;
}

.api-btn {
  background: var(--primary-accent);
  color: #FFF;
  border: none;
  padding: 0.5rem 1rem;
  border-radius: var(--radius-sm);
  font-weight: 600;
  cursor: pointer;
}

/* Interactive Widget 5: LLM Tokenizer */
.tokenizer-container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

.token-box {
  display: flex;
  flex-wrap: wrap;
  gap: 0.3rem;
  background: var(--bg-dark);
  border: 1px solid var(--border-color);
  padding: 1rem;
  border-radius: var(--radius-md);
  min-height: 120px;
}

.token-chip {
  padding: 0.2rem 0.5rem;
  border-radius: 4px;
  font-family: var(--font-code);
  font-size: 0.8rem;
  font-weight: 600;
}

.widget-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

/* Quiz Section Container */
.quiz-section {
  background: var(--bg-surface);
  border: 1px solid var(--border-glow);
  border-radius: var(--radius-lg);
  padding: 2rem;
  margin-top: 3rem;
}

.quiz-question-card {
  background: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
}

.quiz-option-btn {
  width: 100%;
  text-align: left;
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.85rem 1.25rem;
  border-radius: var(--radius-md);
  margin-top: 0.6rem;
  cursor: pointer;
  transition: var(--transition-fast);
  font-size: 0.95rem;
  overflow-wrap: break-word;
  word-break: break-word;
}

.quiz-option-btn:hover {
  border-color: var(--primary-accent);
  background: rgba(99, 102, 241, 0.1);
}

.quiz-option-btn.correct {
  background: rgba(16, 185, 129, 0.15) !important;
  border-color: var(--success-accent) !important;
  color: var(--success-accent) !important;
}

.quiz-option-btn.wrong {
  background: rgba(239, 68, 68, 0.15) !important;
  border-color: #EF4444 !important;
  color: #EF4444 !important;
}

.quiz-explanation {
  margin-top: 0.85rem;
  padding: 0.75rem 1rem;
  background: rgba(99, 102, 241, 0.05);
  border: 1px solid rgba(99, 102, 241, 0.25);
  border-radius: var(--radius-sm);
  font-size: 0.88rem;
  color: var(--text-muted);
}

/* Command Palette Modal (Ctrl+K) */
.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.75);
  backdrop-filter: blur(8px);
  z-index: 200;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding-top: 10vh;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-fast);
}

.modal-backdrop.open {
  opacity: 1;
  pointer-events: auto;
}

.command-modal {
  background: var(--bg-surface);
  border: 1px solid var(--border-glow);
  width: 90%;
  max-width: 650px;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.5);
}

.command-input-wrapper {
  display: flex;
  align-items: center;
  padding: 1rem 1.25rem;
  border-bottom: 1px solid var(--border-color);
}

.command-input {
  background: transparent;
  border: none;
  color: var(--text-main);
  font-size: 1.1rem;
  width: 100%;
  outline: none;
  margin-left: 0.75rem;
}

.command-results {
  max-height: 350px;
  overflow-y: auto;
  padding: 0.5rem;
}

.search-result-item {
  padding: 0.85rem 1rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition-fast);
  color: var(--text-muted);
}

.search-result-item:hover, .search-result-item.selected, .search-result-item.keyboard-active {
  background: rgba(99, 102, 241, 0.15);
  color: var(--text-main);
}

.search-result-title {
  font-weight: 600;
  color: var(--primary-accent);
}

/* Responsive rules consolidated at the bottom of the file */

/* Video Embed Component Styling */
.video-embed-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 0.85rem 1.25rem;
  margin: 1.25rem 0;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.25);
}

.video-body {
  display: none;
}
.video-body.visible {
  display: block;
}

.video-iframe-wrapper {
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
  overflow: hidden;
  border-radius: 12px;
  border: 1px solid var(--border-color);
  margin-top: 0.75rem;
}

.video-iframe-wrapper iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

.video-external-link {
  font-size: 0.75rem;
  color: var(--secondary-accent);
  font-weight: normal;
}

.video-embed-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.video-icon {
  font-size: 1.1rem;
}

.video-link {
  flex: 1;
  font-weight: 600;
  color: var(--text-main) !important;
  border-bottom: none !important;
  text-decoration: none !important;
}

.video-link:hover {
  color: var(--secondary-accent) !important;
  box-shadow: none !important;
}

.video-toggle-btn {
  background: var(--primary-accent);
  color: #FFF;
  border: none;
  padding: 0.35rem 0.85rem;
  border-radius: var(--radius-full);
  font-size: 0.78rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition-fast);
}

.video-toggle-btn:hover {
  background: var(--secondary-accent);
  box-shadow: 0 0 10px var(--primary-glow);
}

/* ============ Lesson Illustrations & SVG Support ============ */

.lesson-illustration {
  margin: 1.5rem 0 1.75rem;
}

.lesson-illustration figure {
  margin: 0;
}

.lesson-illustration img {
  display: block;
  width: 100%;
  max-width: 640px;
  height: auto;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background: #ffffff;
}

.lesson-illustration figcaption {
  margin-top: 0.5rem;
  font-size: 0.82rem;
  color: var(--text-dim);
  max-width: 640px;
}

/* Tool logo tiles — compact app-icon presentation for the vibe roadmap tool lessons */
.lesson-illustration.tool-logo {
  margin: 1.5rem 0 1.25rem;
  text-align: center;
}

.lesson-illustration.tool-logo figure {
  display: inline-block;
  margin: 0 auto;
}

.lesson-illustration.tool-logo img {
  display: block;
  width: auto;
  max-width: 72px;
  max-height: 72px;
  margin: 0 auto;
  padding: 0.5rem;
  border-radius: 12px;
  border: 1px solid var(--border-color);
  background: var(--bg-surface-elevated);
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.22);
}

.lesson-illustration.tool-logo figcaption {
  max-width: 420px;
  margin-left: auto;
  margin-right: auto;
  margin-top: 0.7rem;
}

body.light-theme .lesson-illustration.tool-logo img {
  background: #fff;
  box-shadow: 0 6px 20px rgba(16, 24, 40, 0.1);
}

.interactive-visual {
  margin: 1.5rem 0 1.75rem;
  padding: 1rem 1.25rem 1.25rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background: #1f1d1d;
}

.interactive-visual svg {
  display: block;
}

.illustration-fallback {
  font-size: 0.85rem;
  color: var(--text-dim);
  font-style: italic;
}

/* Support classes referenced by the SVG diagrams in assets/ */
.c-gray { fill: #374151; }
.c-coral { fill: rgba(240, 93, 58, 0.14); }
.th {
  font-family: var(--font-display);
  font-size: 14px;
  font-weight: 600;
  fill: var(--t);
}
.ts {
  font-family: var(--font-body);
  font-size: 12px;
  fill: var(--text-secondary);
}

/* ============ AI Tutor Chat Widget ============ */

.chat-widget {
  position: fixed;
  right: max(1.25rem, env(safe-area-inset-right));
  bottom: max(1.25rem, env(safe-area-inset-bottom));
  z-index: 1000;
  font-family: var(--font-body);
}

.chat-toggle-btn {
  width: 3.5rem;
  height: 3.5rem;
  border-radius: var(--radius-full);
  border: 1px solid var(--border-glow);
  background: linear-gradient(135deg, var(--primary-accent), var(--secondary-accent));
  color: #FFF;
  font-size: 1.5rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 8px 30px var(--primary-glow);
  transition: var(--transition-fast);
}

.chat-toggle-btn:hover {
  transform: translateY(-2px) scale(1.05);
  box-shadow: 0 10px 35px var(--primary-glow);
}

.chat-toggle-btn.hidden {
  display: none;
}

.chat-panel {
  position: absolute;
  right: 0;
  bottom: 4.25rem;
  width: min(380px, calc(100vw - 2rem));
  height: 520px;
  max-height: calc(100vh - 6.5rem);
  display: flex;
  flex-direction: column;
  background: var(--bg-glass);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5);
  overflow: hidden;
  opacity: 0;
  transform: translateY(12px) scale(0.98);
  pointer-events: none;
  transition: var(--transition-fast);
}

.chat-panel.open {
  opacity: 1;
  transform: translateY(0) scale(1);
  pointer-events: auto;
}

.chat-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.9rem 1rem;
  background: linear-gradient(135deg, var(--bg-surface-elevated), var(--bg-surface));
  border-bottom: 1px solid var(--border-color);
}

.chat-header-title {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.chat-header-icon {
  font-size: 1.4rem;
}

.chat-header-name {
  font-weight: 700;
  font-size: 0.95rem;
  line-height: 1.2;
}

.chat-header-status {
  font-size: 0.72rem;
  color: var(--text-dim);
  font-family: var(--font-code);
}

.chat-close-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-size: 0.95rem;
  cursor: pointer;
  padding: 0.25rem 0.4rem;
  border-radius: var(--radius-sm);
  transition: var(--transition-fast);
}

.chat-close-btn:hover {
  color: var(--text-main);
  background: var(--bg-surface-elevated);
}

.chat-messages {
  flex: 1;
  overflow-y: auto;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.chat-msg {
  max-width: 88%;
  padding: 0.65rem 0.85rem;
  border-radius: var(--radius-md);
  font-size: 0.88rem;
  line-height: 1.55;
  word-wrap: break-word;
  overflow-wrap: break-word;
  word-break: break-word;
}

.chat-msg p {
  margin: 0 0 0.5rem;
}

.chat-msg p:last-child {
  margin-bottom: 0;
}

.chat-msg ul,
.chat-msg ol {
  margin: 0.3rem 0 0.5rem;
  padding-left: 1.2rem;
}

.chat-msg pre {
  margin: 0.5rem 0;
  padding: 0.65rem 0.8rem;
  border-radius: var(--radius-sm);
  background: var(--bg-dark);
  border: 1px solid var(--border-color);
  overflow-x: auto;
  font-family: var(--font-code);
  font-size: 0.78rem;
  line-height: 1.5;
}

.chat-msg code {
  font-family: var(--font-code);
  font-size: 0.82em;
  background: var(--bg-surface-elevated);
  padding: 0.1rem 0.3rem;
  border-radius: 4px;
}

.chat-msg pre code {
  background: transparent;
  padding: 0;
  font-size: 0.78rem;
}

.chat-msg-bot {
  align-self: flex-start;
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-color);
  color: var(--text-main);
}

.chat-msg-user {
  align-self: flex-end;
  background: linear-gradient(135deg, var(--primary-accent), #4F46E5);
  color: #FFF;
}

.chat-msg-typing {
  display: flex;
  gap: 0.3rem;
  align-items: center;
  padding: 0.8rem 0.9rem;
}

.typing-dot {
  width: 7px;
  height: 7px;
  border-radius: var(--radius-full);
  background: var(--text-muted);
  animation: chat-typing 1.2s infinite ease-in-out;
}

.typing-dot:nth-child(2) {
  animation-delay: 0.15s;
}

.typing-dot:nth-child(3) {
  animation-delay: 0.3s;
}

@keyframes chat-typing {
  0%, 60%, 100% {
    transform: translateY(0);
    opacity: 0.4;
  }
  30% {
    transform: translateY(-4px);
    opacity: 1;
  }
}

.chat-input-row {
  display: flex;
  gap: 0.5rem;
  padding: 0.75rem;
  border-top: 1px solid var(--border-color);
  background: var(--bg-glass);
}

.chat-input {
  flex: 1;
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-main);
  padding: 0.6rem 0.85rem;
  font-family: var(--font-body);
  font-size: 0.88rem;
  outline: none;
  transition: var(--transition-fast);
}

.chat-input:focus {
  border-color: var(--primary-accent);
  box-shadow: 0 0 0 3px var(--primary-glow);
}

.chat-input::placeholder {
  color: var(--text-dim);
}

.chat-send-btn {
  width: 2.6rem;
  height: 2.6rem;
  border: none;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--primary-accent), var(--secondary-accent));
  color: #FFF;
  font-size: 1rem;
  cursor: pointer;
  flex-shrink: 0;
  transition: var(--transition-fast);
}

.chat-send-btn:hover {
  box-shadow: 0 0 12px var(--primary-glow);
}

.chat-send-btn:disabled {
  opacity: 0.5;
  cursor: default;
  box-shadow: none;
}

.leader { stroke: var(--border-strong); }

/* ============ Welcome Overlay ============ */

.welcome-overlay {
  position: fixed;
  inset: 0;
  z-index: 5000;
  background: var(--bg-dark);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: opacity 0.4s ease, visibility 0.4s ease;
}

.welcome-overlay.hidden {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.welcome-card {
  text-align: center;
  max-width: 600px;
  width: 100%;
  padding: 3rem 2.5rem;
  animation: welcome-fade-in 0.6s ease-out;
}

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

.welcome-badge {
  display: inline-block;
  background: linear-gradient(135deg, var(--primary-accent), var(--secondary-accent));
  color: #FFF;
  padding: 0.35rem 1rem;
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 1px;
  margin-bottom: 1.5rem;
}

.welcome-title {
  font-size: 2.5rem;
  margin-bottom: 0.75rem;
  overflow-wrap: break-word;
  word-break: break-word;
  color: var(--text-main);
}

.welcome-subtitle {
  color: var(--text-muted);
  font-size: 1.1rem;
  margin-bottom: 2.5rem;
  line-height: 1.6;
}

.welcome-features {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  text-align: left;
  margin-bottom: 2.5rem;
}

.welcome-feature-item {
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem;
}

.welcome-feature-icon {
  font-size: 1.5rem;
  flex-shrink: 0;
}

.welcome-feature-item strong {
  display: block;
  color: var(--text-main);
  font-size: 0.9rem;
  margin-bottom: 0.2rem;
}

.welcome-feature-item p {
  color: var(--text-muted);
  font-size: 0.78rem;
  margin: 0;
  line-height: 1.4;
}

.welcome-start-btn {
  background: linear-gradient(135deg, var(--primary-accent), var(--secondary-accent));
  color: #FFF;
  border: none;
  padding: 0.9rem 2.5rem;
  border-radius: var(--radius-full);
  font-size: 1.1rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
  box-shadow: 0 8px 30px var(--primary-glow);
}

.welcome-start-btn:hover {
  transform: translateY(-2px) scale(1.03);
  box-shadow: 0 12px 40px var(--primary-glow);
}

.welcome-note {
  margin-top: 1rem;
  font-size: 0.78rem;
  color: var(--text-dim);
}

@media (max-width: 600px) {
  .welcome-features { grid-template-columns: 1fr; }
  .welcome-title { font-size: 1.8rem; }
  .welcome-card { padding: 2rem 1.5rem; }
}

/* ============ Hamburger Menu ============ */

.nav-left {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.hamburger-btn {
  display: none;
  flex-direction: column;
  gap: 4px;
  background: transparent;
  border: none;
  cursor: pointer;
  padding: 0.4rem;
  z-index: 110;
}

.hamburger-line {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--text-main);
  border-radius: 2px;
  transition: transform 0.2s, opacity 0.2s;
}

.hamburger-btn.active .hamburger-line:nth-child(1) {
  transform: rotate(45deg) translate(4px, 4px);
}
.hamburger-btn.active .hamburger-line:nth-child(2) {
  opacity: 0;
}
.hamburger-btn.active .hamburger-line:nth-child(3) {
  transform: rotate(-45deg) translate(4px, -4px);
}

/* ============ Progress Ring (Nav) ============ */

.progress-ring-container {
  position: relative;
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.progress-ring-bg {
  fill: none;
  stroke: var(--bg-surface-elevated);
  stroke-width: 3;
}

.progress-ring-fill {
  fill: none;
  stroke: var(--success-accent);
  stroke-width: 3;
  stroke-linecap: round;
  stroke-dasharray: 87.96;
  stroke-dashoffset: 87.96;
  transform: rotate(-90deg);
  transform-origin: center;
  transition: stroke-dashoffset 0.6s ease;
}

.progress-ring-text {
  position: absolute;
  font-size: 0.55rem;
  font-weight: 700;
  color: var(--text-main);
  font-family: var(--font-code);
}

/* ============ Theme Toggle ============ */

.theme-toggle-btn {
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: var(--transition-fast);
  font-size: 1rem;
}

.theme-toggle-btn:hover {
  border-color: var(--primary-accent);
  box-shadow: 0 0 10px var(--primary-glow);
}

/* Light theme overrides */
body.light-theme {
  --bg-dark: #F8FAFC;
  --bg-surface: #FFFFFF;
  --bg-surface-elevated: #F1F5F9;
  --bg-glass: rgba(255, 255, 255, 0.85);
  --border-color: rgba(0, 0, 0, 0.1);
  --border-glow: rgba(99, 102, 241, 0.3);
  --text-main: #1E293B;
  --text-muted: #475569;
  --text-dim: #94A3B8;
  --surface-0: #F8FAFC;
  --surface-1: #F1F5F9;
  --border-strong: rgba(0, 0, 0, 0.15);
  --text-secondary: #475569;
}

body.light-theme pre {
  background: #F1F5F9 !important;
  border-color: rgba(0, 0, 0, 0.1);
}

body.light-theme pre code {
  color: var(--text-main);
}

body.light-theme .sandbox-preview {
  background: #FFF;
}

body.light-theme .lesson-illustration img {
  background: #FFF;
}

body.light-theme .interactive-visual {
  background: #F1F5F9;
}

/* ============ Sidebar Improvements ============ */

.sidebar-header {
  margin-bottom: 1rem;
}

.sidebar-progress-bar {
  height: 4px;
  background: var(--bg-surface-elevated);
  border-radius: 2px;
  margin: 0.75rem 0.5rem 0.4rem;
  overflow: hidden;
}

.sidebar-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary-accent), var(--success-accent));
  border-radius: 2px;
  width: 100%;
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.5s ease;
}

.sidebar-progress-label {
  font-size: 0.72rem;
  color: var(--text-dim);
  padding-left: 0.5rem;
}

.sidebar-footer {
  margin-top: 1.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.sidebar-bookmarks-btn,
.sidebar-reset-btn {
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  padding: 0.5rem 0.75rem;
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  cursor: pointer;
  transition: var(--transition-fast);
  text-align: left;
}

.sidebar-bookmarks-btn:hover,
.sidebar-reset-btn:hover {
  border-color: var(--primary-accent);
  color: var(--text-main);
}

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: 85;
}

/* ============ Stage Navigation (Next/Prev) ============ */

.stage-nav-buttons {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
}

.stage-nav-btn {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 1rem 1.25rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition-fast);
  flex: 1;
  max-width: 48%;
}

.stage-nav-btn:hover {
  border-color: var(--primary-accent);
  box-shadow: var(--shadow-glow);
}

.stage-nav-btn.next {
  text-align: right;
  justify-content: flex-end;
  margin-left: auto;
}

.stage-nav-btn-label {
  font-size: 0.72rem;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.stage-nav-btn-title {
  font-weight: 600;
  font-size: 0.9rem;
}

/* ============ Quiz Score Summary ============ */

.quiz-summary {
  background: var(--bg-dark);
  border: 1px solid var(--border-glow);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  text-align: center;
  margin-top: 1rem;
}

.quiz-summary-score {
  font-size: 2.5rem;
  font-weight: 800;
  font-family: var(--font-display);
  margin-bottom: 0.5rem;
}

.quiz-summary-score.perfect {
  color: var(--success-accent);
}

.quiz-summary-score.good {
  color: var(--success-accent);
}

.quiz-summary-score.needs-work {
  color: var(--warning-accent);
}

.quiz-summary-label {
  font-size: 0.9rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

.quiz-retake-btn {
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.6rem 1.5rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  font-weight: 600;
  transition: var(--transition-fast);
}

.quiz-retake-btn:hover {
  border-color: var(--primary-accent);
  box-shadow: 0 0 10px var(--primary-glow);
}

/* ============ Bookmark Button in Lessons ============ */

.lesson-bookmark-btn {
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-dim);
  padding: 0.3rem 0.6rem;
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  cursor: pointer;
  transition: var(--transition-fast);
  float: right;
  margin-top: 0.25rem;
}

.lesson-bookmark-btn:hover,
.lesson-bookmark-btn.active {
  color: var(--warning-accent);
  border-color: var(--warning-accent);
}

/* ============ Bookmarks Panel ============ */

.bookmarks-panel {
  position: fixed;
  top: 64px;
  right: 0;
  bottom: 0;
  width: min(360px, 90vw);
  background: var(--bg-surface);
  border-left: 1px solid var(--border-color);
  z-index: 95;
  transform: translateX(100%);
  transition: transform 0.3s ease;
  overflow-y: auto;
  padding: 1.5rem;
}

.bookmarks-panel.open {
  transform: translateX(0);
}

.bookmarks-panel-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.bookmarks-panel-title {
  font-size: 1.1rem;
  font-weight: 700;
  font-family: var(--font-display);
}

.bookmarks-panel-close {
  background: transparent;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1rem;
}

.bookmark-item {
  background: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 0.75rem;
  margin-bottom: 0.5rem;
  cursor: pointer;
  transition: var(--transition-fast);
}

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

.bookmark-item-stage {
  font-size: 0.7rem;
  color: var(--text-dim);
}

.bookmark-item-title {
  font-weight: 600;
  font-size: 0.85rem;
  color: var(--text-main);
}

.bookmarks-empty {
  text-align: center;
  color: var(--text-dim);
  font-size: 0.85rem;
  padding: 2rem 0;
}

/* ============ Challenge Exercise Styling ============ */

.challenge-card {
  background: var(--bg-dark);
  border: 1px solid var(--warning-accent);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  margin: 1.5rem 0;
}

.challenge-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

.challenge-badge {
  background: var(--warning-accent);
  color: #000;
  font-size: 0.65rem;
  font-weight: 800;
  padding: 0.15rem 0.5rem;
  border-radius: var(--radius-full);
  text-transform: uppercase;
}

.challenge-title {
  font-weight: 700;
  font-size: 1rem;
  color: var(--text-main);
}

.challenge-body {
  color: var(--text-muted);
  font-size: 0.9rem;
  line-height: 1.6;
  overflow-wrap: break-word;
  word-break: break-word;
}

.challenge-hint {
  margin-top: 0.75rem;
  padding: 0.6rem 0.8rem;
  background: rgba(245, 158, 11, 0.05);
  border: 1px solid rgba(245, 158, 11, 0.25);
  border-radius: var(--radius-sm);
  font-size: 0.82rem;
  color: var(--text-muted);
  display: none;
}

.challenge-hint.visible {
  display: block;
}

.challenge-hint-btn {
  background: transparent;
  border: 1px solid var(--warning-accent);
  color: var(--warning-accent);
  padding: 0.3rem 0.75rem;
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  cursor: pointer;
  margin-top: 0.5rem;
  transition: var(--transition-fast);
}

.challenge-hint-btn:hover {
  background: rgba(245, 158, 11, 0.1);
}

/* ============ Key Terms Glossary Tooltip ============ */

.term-tooltip {
  position: relative;
  border-bottom: 1px dashed var(--secondary-accent);
  cursor: help;
  color: var(--secondary-accent);
}

.term-tooltip .tooltip-text {
  visibility: hidden;
  opacity: 0;
  position: absolute;
  bottom: 120%;
  left: 50%;
  transform: translateX(-50%);
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-glow);
  color: var(--text-main);
  padding: 0.6rem 0.8rem;
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  width: max-content;
  max-width: 280px;
  z-index: 50;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.3);
  transition: opacity 0.2s;
}

.term-tooltip:hover .tooltip-text {
  visibility: visible;
  opacity: 1;
}

/* ============ Responsive (Mobile) ============ */

@media (max-width: 900px) {
  .hamburger-btn {
    display: flex;
  }
  .sidebar {
    transform: translateX(-100%);
  }
  .sidebar.mobile-open {
    transform: translateX(0);
    box-shadow: 4px 0 20px rgba(0, 0, 0, 0.3);
  }
  .sidebar.mobile-open ~ .sidebar-overlay {
    display: block;
  }
  .main-viewport {
    margin-left: 0;
    padding: 1.25rem 1.5rem 4rem;
  }
  .sandbox-layout, .api-inspector-grid, .tokenizer-container, .widget-grid {
    grid-template-columns: 1fr;
  }
  .sandbox-layout {
    height: auto;
  }
  .sandbox-editor {
    min-height: 240px;
  }
  .sandbox-preview {
    height: 340px;
  }
  .stage-hero {
    padding: 1.5rem 1.5rem;
  }
  .brand-text {
    display: none;
  }
  .stage-nav-buttons {
    flex-direction: column;
  }
  .stage-nav-btn {
    max-width: 100%;
  }
  .search-trigger-btn span:first-child {
    display: none;
  }
}

/* ============ Tablet Breakpoint (<=768px) ============ */

@media (max-width: 768px) {
  .stage-title {
    font-size: 1.75rem;
  }
  .stage-subtitle {
    font-size: 1rem;
  }
  .module-card, .quiz-section, .interactive-lab {
    padding: 1.5rem;
  }
  .network-sim-grid {
    grid-template-columns: 1fr;
    gap: 0.75rem;
    padding: 1rem;
  }
  .network-sim-grid .sim-node {
    padding: 1rem;
  }
  .network-sim-grid .sim-pipe {
    display: none;
  }
  .chat-panel {
    width: min(440px, calc(100vw - 1.5rem));
  }
  .command-results {
    max-height: 45vh;
  }
}

/* ============ Phone Breakpoint (<=480px) ============ */

@media (max-width: 480px) {
  html, body {
    font-size: 14px;
  }
  .top-nav {
    padding: 0 0.85rem;
  }
  .nav-actions {
    gap: 0.6rem;
  }
  .search-trigger-btn {
    padding: 0.45rem 0.6rem;
  }
  .search-trigger-btn .kbd-shortcut {
    display: none;
  }
  .main-viewport {
    padding: 1rem 1rem 3.5rem;
  }
  .stage-hero {
    padding: 1.25rem 1rem;
    margin-bottom: 1.5rem;
  }
  .stage-title {
    font-size: 1.45rem;
  }
  .stage-subtitle {
    font-size: 0.92rem;
  }
  .module-card {
    padding: 1.25rem;
    margin-bottom: 1.5rem;
  }
  .module-title {
    font-size: 1.15rem;
  }
  .lesson-title {
    font-size: 1.05rem;
  }
  .interactive-lab, .quiz-section {
    padding: 1.25rem;
    margin: 1.5rem 0;
  }
  .lab-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.5rem;
  }
  pre {
    font-size: 0.78rem;
    padding: 1rem;
  }
  .quiz-option-btn {
    padding: 0.85rem 1rem;
    font-size: 0.95rem;
  }
  .sandbox-editor {
    min-height: 220px;
  }
  .sandbox-preview {
    height: 300px;
  }
  .flashcard-container {
    height: 240px;
  }
  .stage-nav-btn {
    padding: 0.85rem 1rem;
  }
  .sidebar {
    width: min(320px, 85vw);
  }
  .sidebar-bookmarks-btn, .sidebar-reset-btn {
    padding: 0.7rem 0.85rem;
    font-size: 0.85rem;
  }
  .term-tooltip .tooltip-text {
    left: 0;
    transform: none;
    max-width: 80vw;
  }
  .command-modal {
    width: 96%;
  }
  .command-input, .chat-input, .sandbox-textarea {
    font-size: 16px;
  }
  .welcome-title {
    font-size: 1.6rem;
  }
  .welcome-subtitle {
    font-size: 0.98rem;
  }
  .welcome-start-btn {
    width: 100%;
    max-width: 320px;
  }
  .welcome-card {
    padding: 1.75rem 1.25rem;
  }

  /* Full-screen AI Tutor chat panel */
  .chat-panel {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    height: 100vh;
    height: 100dvh;
    max-height: 100vh;
    max-height: 100dvh;
    border-radius: 0;
    border: none;
  }
  .chat-toggle-btn {
    width: 3.25rem;
    height: 3.25rem;
  }
  .chat-input-row {
    padding-bottom: calc(0.75rem + env(safe-area-inset-bottom));
  }
  .chat-send-btn {
    width: 3rem;
    height: 3rem;
  }

  /* Full-width bookmarks panel */
  .bookmarks-panel {
    width: 100%;
    border-left: none;
  }
  .bookmark-item {
    padding: 0.9rem;
  }
}

/* ============ Stage Transition Animation ============ */

@keyframes stage-fade-in {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

.stage-hero {
  animation: stage-fade-in 0.3s ease-out;
}

.module-card {
  animation: stage-fade-in 0.4s ease-out;
}

/* ============ Flashcard Widget ============ */

.flashcard-container {
  perspective: 1000px;
  width: 100%;
  max-width: 400px;
  height: 220px;
  margin: 1rem auto;
  cursor: pointer;
}

.flashcard-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transition: transform 0.6s;
  transform-style: preserve-3d;
}

.flashcard-inner.flipped {
  transform: rotateY(180deg);
}

.flashcard-front,
.flashcard-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  border-radius: var(--radius-md);
  padding: 1.5rem;
  text-align: center;
}

.flashcard-front {
  background: var(--bg-dark);
  border: 2px solid var(--primary-accent);
}

.flashcard-back {
  background: var(--bg-dark);
  border: 2px solid var(--success-accent);
  transform: rotateY(180deg);
}

.flashcard-term {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text-main);
}

.flashcard-hint {
  font-size: 0.78rem;
  color: var(--text-dim);
  margin-top: 0.5rem;
}

.flashcard-definition {
  font-size: 0.95rem;
  color: var(--text-muted);
  line-height: 1.5;
}

.flashcard-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  margin-top: 1rem;
}

.flashcard-nav-btn {
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.4rem 1rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition-fast);
}

.flashcard-nav-btn:hover {
  border-color: var(--primary-accent);
}

.flashcard-counter {
  font-size: 0.8rem;
  color: var(--text-dim);
  font-family: var(--font-code);
}

/* ============ Roadmap Switcher (Full Course / Vibe Coding) ============ */
.roadmap-switcher {
  display: flex;
  gap: 0.2rem;
  margin-bottom: 0.85rem;
  padding: 0.22rem;
  background: var(--bg-surface-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-full);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

.roadmap-switcher-btn {
  flex: 1;
  min-width: 0;
  padding: 0.42rem 0.3rem;
  font-size: 0.76rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  color: var(--text-dim);
  background: transparent;
  border: none;
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: background 0.2s ease, color 0.2s ease, box-shadow 0.2s ease;
  text-align: center;
  white-space: nowrap;
  -webkit-tap-highlight-color: transparent;
}

.roadmap-switcher-btn:hover {
  color: var(--text-muted);
  background: rgba(255, 255, 255, 0.05);
}

.roadmap-switcher-btn.active {
  background: var(--bg-glass);
  color: var(--text-main);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.3), inset 0 1px 0 rgba(255, 255, 255, 0.1);
}

/* ============ Welcome overlay: choose your path ============ */
.welcome-paths {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.7rem;
  margin-top: 0.4rem;
}

.welcome-vibe-btn {
  background: transparent;
  color: var(--primary-accent);
  border: 2px solid var(--primary-accent);
  padding: 0.7rem 2rem;
  border-radius: var(--radius-full);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s ease, color 0.2s ease, transform 0.2s ease;
}

.welcome-vibe-btn:hover {
  background: var(--primary-accent);
  color: #fff;
  transform: translateY(-1px);
}

/* ============ Minimal roadmap mode: hide progress/bookmark/reset machinery ============ */
body.minimal-roadmap .progress-ring-container,
body.minimal-roadmap .sidebar-progress-bar,
body.minimal-roadmap .sidebar-progress-label,
body.minimal-roadmap .sidebar-footer {
  display: none !important;
}

@media (max-width: 480px) {
  .welcome-vibe-btn {
    width: 100%;
    max-width: 320px;
  }
}

/* ============ Apple-style polish: links, media, motion ============ */

/* Doc links (link text is a domain/path, e.g. "docs.cursor.com") become pills */
.lesson-body a.doc-pill {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  margin: 0.1rem 0.05rem;
  padding: 0.18rem 0.65rem;
  border-radius: var(--radius-full);
  background: rgba(6, 182, 212, 0.08);
  border: 1px solid rgba(6, 182, 212, 0.22);
  color: var(--secondary-accent);
  text-decoration: none;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  transition: var(--transition-fast);
}

.lesson-body a.doc-pill:hover {
  background: rgba(6, 182, 212, 0.16);
  border-color: rgba(6, 182, 212, 0.45);
  color: var(--secondary-accent);
  box-shadow: 0 2px 8px rgba(6, 182, 212, 0.18);
}

/* Plain-word links keep a subtle Apple-style underline */
.lesson-body a.text-link {
  color: var(--secondary-accent);
  text-decoration: underline;
  text-decoration-color: rgba(6, 182, 212, 0.35);
  text-underline-offset: 2px;
  font-weight: 500;
}

.lesson-body a.text-link:hover {
  color: var(--primary-accent);
  text-decoration-color: currentColor;
}

/* Internal stage links ([text](#stage-id)) */
.lesson-body a.stage-link {
  color: var(--primary-accent);
  text-decoration: underline;
  text-decoration-color: rgba(99, 102, 241, 0.4);
  text-underline-offset: 2px;
  font-weight: 600;
}

.lesson-body a.stage-link:hover {
  text-decoration-color: currentColor;
  box-shadow: 0 2px 0 rgba(99, 102, 241, 0.2);
}

/* Light theme: video cards and switcher sit on white */
body.light-theme .video-embed-card {
  background: #fff;
  box-shadow: 0 1px 2px rgba(16, 24, 40, 0.08);
}

body.light-theme .roadmap-switcher {
  background: var(--bg-surface-elevated);
}

body.light-theme .roadmap-switcher-btn:hover {
  background: rgba(16, 24, 40, 0.06);
}

body.light-theme .roadmap-switcher-btn.active {
  background: #fff;
  box-shadow: 0 1px 3px rgba(16, 24, 40, 0.16), inset 0 1px 0 rgba(255, 255, 255, 0.6);
}

body.light-theme .module-card:hover {
  box-shadow: 0 12px 32px rgba(16, 24, 40, 0.1);
}

/* Respect reduced-motion preferences */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* ============================================================
   INTERACTIVE LESSON SYSTEM (Lab Bench, breadcrumbs, TOC, XP)
   Append-only layer: no rules above are modified.
   ============================================================ */

/* ---------- Breadcrumb trail ---------- */
.breadcrumb-trail {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.4rem;
  font-size: 0.82rem;
  color: var(--text-dim);
  margin-bottom: 0.9rem;
}
.crumb { color: var(--text-muted); }
a.crumb {
  color: var(--secondary-accent);
  text-decoration: none;
  border-bottom: 1px dashed rgba(6, 182, 212, 0.4);
}
a.crumb:hover { color: var(--primary-accent); border-bottom-color: var(--primary-accent); }
.crumb-root { font-weight: 600; letter-spacing: 0.02em; }
.crumb-current { color: var(--text-main); font-weight: 600; }
.crumb-sep { opacity: 0.5; }

/* ---------- Lab Bench signature frame ---------- */
.lab-bench {
  position: relative;
  background:
    linear-gradient(180deg, rgba(99, 102, 241, 0.03), transparent 42%),
    var(--bg-surface-elevated);
  border: 1px solid rgba(245, 158, 11, 0.4);
  border-radius: var(--radius-md);
  padding: 1.1rem 1.25rem 1.25rem;
  margin: 1.25rem 0;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}
.lab-bench:hover {
  border-color: rgba(245, 158, 11, 0.6);
  box-shadow: 0 0 15px rgba(245, 158, 11, 0.1);
}
.lab-bench.solved {
  border-color: rgba(16, 185, 129, 0.5);
}
.lab-bench.solved:hover {
  border-color: rgba(16, 185, 129, 0.7);
  box-shadow: 0 0 15px rgba(16, 185, 129, 0.15);
}
.lab-bench.solved .bench-top { opacity: 0.92; }

.bench-top {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  margin-bottom: 0.75rem;
}
.bench-led {
  width: 9px; height: 9px;
  border-radius: 50%;
  background: var(--warning-accent);
  box-shadow: 0 0 8px rgba(245, 158, 11, 0.7);
  animation: led-pulse 1.6s ease-in-out infinite;
  flex: none;
}
.lab-bench.solved .bench-led {
  background: var(--success-accent);
  box-shadow: none;
  animation: none;
}
@keyframes led-pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.35; }
}

.bench-kind {
  font-size: 0.68rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--text-dim);
  white-space: nowrap;
}
.bench-title {
  font-weight: 600;
  color: var(--text-main);
  font-size: 0.95rem;
  min-width: 0;
  overflow-wrap: break-word;
}
.bench-xp {
  margin-left: auto;
  font-family: var(--font-code);
  font-size: 0.72rem;
  color: var(--warning-accent);
  background: rgba(245, 158, 11, 0.12);
  border: 1px solid rgba(245, 158, 11, 0.35);
  padding: 0.12rem 0.5rem;
  border-radius: var(--radius-full);
  white-space: nowrap;
}
.lab-bench.solved .bench-xp {
  color: var(--success-accent);
  background: rgba(16, 185, 129, 0.12);
  border-color: rgba(16, 185, 129, 0.35);
}

.bench-intro { color: var(--text-muted); font-size: 0.92rem; margin-bottom: 0.75rem; }
.bench-q { color: var(--text-main); font-weight: 600; font-size: 0.98rem; margin-bottom: 0.75rem; }

.bench-code {
  margin: 0.75rem 0 !important;
  padding: 0.9rem 1rem !important;
}
.bench-done-banner {
  margin-top: 0.85rem;
  padding: 0.55rem 0.85rem;
  background: rgba(16, 185, 129, 0.05);
  border: 1px solid rgba(16, 185, 129, 0.3);
  border-radius: var(--radius-sm);
  color: var(--success-accent);
  font-size: 0.88rem;
  font-weight: 600;
}

/* ---------- Multiple choice (checkpoint / predict) ---------- */
.mc-options { display: grid; gap: 0.45rem; }
.mc-option {
  display: flex; align-items: baseline; gap: 0.6rem;
  text-align: left;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.6rem 0.9rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.92rem;
  transition: var(--transition-fast);
}
.mc-option:hover:not(:disabled) { border-color: var(--primary-accent); background: rgba(99, 102, 241, 0.08); }
.mc-option:disabled { cursor: default; opacity: 0.75; }
.mc-option.correct {
  border-color: var(--success-accent) !important;
  background: rgba(16, 185, 129, 0.12) !important;
  color: var(--success-accent) !important;
  opacity: 1;
}
.mc-option.wrong {
  border-color: #EF4444 !important;
  background: rgba(239, 68, 68, 0.1) !important;
  color: #EF4444 !important;
  text-decoration: line-through;
  opacity: 0.65;
}
.mc-letter {
  font-family: var(--font-code);
  font-size: 0.72rem;
  color: var(--text-dim);
  flex: none;
}
.mc-option.correct .mc-letter { color: var(--success-accent); }
.mc-option.wrong .mc-letter { color: #EF4444; }

.bench-explain {
  margin-top: 0.75rem;
  padding: 0.6rem 0.85rem;
  background: rgba(99, 102, 241, 0.04);
  border: 1px solid rgba(99, 102, 241, 0.25);
  border-radius: var(--radius-sm);
  font-size: 0.88rem;
  color: var(--text-muted);
}

/* ---------- Fill-in-the-blank challenge ---------- */
.blank-input {
  background: rgba(245, 158, 11, 0.07);
  border: none;
  border-bottom: 2px dashed var(--warning-accent);
  color: var(--text-main);
  font-family: var(--font-code);
  font-size: 0.88em;
  padding: 0.1rem 0.35rem;
  outline: none;
  vertical-align: baseline;
}
.blank-input:focus { border-bottom-style: solid; }
.blank-input.ok { border-bottom-color: var(--success-accent); color: var(--success-accent); }
.blank-input.bad { border-bottom-color: #EF4444; color: #EF4444; }

.challenge-actions { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 0.85rem; }
.challenge-actions .api-btn { font-size: 0.82rem; padding: 0.45rem 0.95rem; }
.btn-hint { background: var(--warning-accent) !important; color: #111 !important; }
.btn-show { background: transparent !important; border: 1px dashed var(--border-strong) !important; color: var(--text-muted) !important; }
.hint-area p, .bench-explain p { margin: 0.3rem 0; font-size: 0.88rem; }

/* ---------- Sort / ordering ---------- */
.sort-slots {
  list-style: none;
  margin: 0 0 0.75rem;
  padding: 0.6rem;
  min-height: 2.4rem;
  background: var(--bg-dark);
  border: 1px dashed var(--border-strong);
  border-radius: var(--radius-sm);
}
.slot-empty { color: var(--text-dim); font-size: 0.82rem; }
.sort-placed {
  display: inline-flex; align-items: center; gap: 0.5rem;
  background: rgba(99, 102, 241, 0.15);
  border: 1px solid var(--primary-accent);
  color: var(--text-main);
  border-radius: var(--radius-sm);
  padding: 0.3rem 0.6rem;
  margin: 0.15rem;
  cursor: pointer;
  font-size: 0.86rem;
}
.sort-n { font-family: var(--font-code); font-size: 0.72rem; color: var(--primary-accent); }
.sort-pool { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-bottom: 0.5rem; }
.sort-tile {
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  color: var(--text-main);
  border-radius: var(--radius-sm);
  padding: 0.35rem 0.7rem;
  cursor: pointer;
  font-size: 0.88rem;
  transition: var(--transition-fast);
}
.sort-tile:hover { border-color: var(--primary-accent); transform: translateY(-1px); }
.btn-reset { background: transparent !important; border: 1px solid var(--border-color) !important; color: var(--text-muted) !important; }

/* ---------- Matching pairs ---------- */
.match-hintline { color: var(--text-dim); font-size: 0.82rem; margin-bottom: 0.6rem; }
.match-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; }
.match-col { display: flex; flex-direction: column; gap: 0.45rem; }
.match-item {
  text-align: left;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  border-radius: var(--radius-sm);
  padding: 0.55rem 0.8rem;
  cursor: pointer;
  font-size: 0.9rem;
  transition: var(--transition-fast);
}
.match-item:hover:not(:disabled) { border-color: var(--primary-accent); }
.match-item.selected { border-color: var(--warning-accent); background: rgba(245, 158, 11, 0.1); }
.match-item.matched {
  border-color: var(--success-accent);
  background: rgba(16, 185, 129, 0.08);
  color: var(--success-accent);
  cursor: default;
}
@keyframes match-shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-3px); }
  75% { transform: translateX(3px); }
}
.match-item.shake { animation: match-shake 0.3s ease-in-out; border-color: #EF4444; }

/* ---------- Guided steps ---------- */
.steps-walker { display: flex; flex-direction: column; gap: 0.4rem; margin-top: 0.25rem; }
.step-row { border: 1px solid var(--border-color); border-radius: var(--radius-sm); overflow: hidden; background: var(--bg-surface); }
.step-head {
  display: flex; align-items: center; gap: 0.65rem;
  width: 100%;
  background: transparent;
  border: none;
  color: var(--text-main);
  padding: 0.6rem 0.8rem;
  cursor: pointer;
  text-align: left;
  font-size: 0.92rem;
}
.step-num {
  font-family: var(--font-code);
  font-size: 0.72rem;
  color: var(--secondary-accent);
  border: 1px solid var(--border-strong);
  border-radius: 50%;
  width: 22px; height: 22px;
  display: inline-flex; align-items: center; justify-content: center;
  flex: none;
}
.step-body {
  display: none;
  padding: 0 0.8rem 0.75rem 2.5rem;
  color: var(--text-muted);
  font-size: 0.9rem;
}
.step-row.open .step-body { display: block; }
.step-row.visited .step-num { color: var(--success-accent); border-color: var(--success-accent); }
.btn-steps-done { background: var(--primary-accent) !important; }

/* ---------- Prompt lab ---------- */
.prompt-vague {
  border: 1px solid rgba(239, 68, 68, 0.3);
  background: rgba(239, 68, 68, 0.04);
  color: var(--text-main);
  padding: 0.55rem 0.9rem;
  border-radius: var(--radius-sm);
  margin: 0 0 0.75rem;
  font-size: 0.92rem;
}
.prompt-input {
  width: 100%;
  background: var(--bg-dark);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  border-radius: var(--radius-sm);
  padding: 0.7rem 0.85rem;
  font-family: var(--font-body);
  font-size: 0.9rem;
  resize: vertical;
  outline: none;
}
.prompt-input:focus { border-color: var(--primary-accent); }
.keyword-report { margin-top: 0.75rem; font-size: 0.88rem; color: var(--text-muted); }
.keyword-report .kw-found { color: var(--success-accent); }
.keyword-report .kw-missing { color: var(--warning-accent); }
.model-answer {
  margin-top: 0.75rem;
  padding: 0.7rem 0.9rem;
  background: rgba(99, 102, 241, 0.04);
  border: 1px solid rgba(99, 102, 241, 0.25);
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  color: var(--text-muted);
}
.model-answer strong { color: var(--text-main); }
.model-answer p { margin: 0.35rem 0 0; }
.btn-model { background: transparent !important; border: 1px dashed var(--border-strong) !important; color: var(--text-muted) !important; }

/* ---------- Lesson head row + done toggle ---------- */
.lesson-head-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 0.75rem;
  scroll-margin-top: 90px;
}
.lesson-title { margin-bottom: 0 !important; }
.lesson-done-btn {
  flex: none;
  display: inline-flex; align-items: center; gap: 0.4rem;
  background: transparent;
  border: 1px solid var(--border-strong);
  color: var(--text-dim);
  border-radius: var(--radius-full);
  padding: 0.28rem 0.8rem;
  font-size: 0.78rem;
  cursor: pointer;
  transition: var(--transition-fast);
}
.lesson-done-btn:hover { border-color: var(--success-accent); color: var(--success-accent); }
.done-check { display: none; font-size: 0.8em; }
.lesson-done-btn.done {
  border-color: var(--success-accent);
  color: var(--success-accent);
  background: rgba(16, 185, 129, 0.08);
}
.lesson-done-btn.done .done-check { display: inline; }

/* ---------- TOC rail ---------- */
.toc-rail {
  float: right;
  width: 230px;
  margin: 0 0 1rem 1.5rem;
  padding: 0.9rem 1rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  position: sticky;
  top: 84px;
  max-height: calc(100vh - 110px);
  overflow-y: auto;
  font-size: 0.82rem;
}
.toc-title {
  font-size: 0.68rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--text-dim);
  margin-bottom: 0.5rem;
}
.toc-link {
  display: block;
  color: var(--text-muted);
  text-decoration: none;
  padding: 0.22rem 0.5rem;
  border-left: 2px solid transparent;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  line-height: 1.35;
  margin-left: 0.4rem;
}
.toc-link:hover { color: var(--text-main); background: rgba(99, 102, 241, 0.08); }
.toc-link.active { color: var(--primary-accent); border-left-color: var(--primary-accent); background: rgba(99, 102, 241, 0.1); }
.toc-module {
  font-weight: 700;
  color: var(--text-main);
  margin-top: 0.5rem;
}
.toc-lesson { padding-left: 1.1rem; }
.toc-dot {
  display: inline-block;
  width: 6px; height: 6px;
  border-radius: 50%;
  background: var(--warning-accent);
  margin-right: 0.4rem;
  vertical-align: middle;
}
.module-card, .lesson-block { scroll-margin-top: 84px; }
#interactive-lab-mount { scroll-margin-top: 84px; }

/* ---------- XP chip (top nav) ---------- */
.xp-chip {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background: rgba(245, 158, 11, 0.1);
  border: 1px solid rgba(245, 158, 11, 0.4);
  color: var(--warning-accent);
  border-radius: var(--radius-full);
  padding: 0.32rem 0.8rem;
  font-family: var(--font-code);
  font-size: 0.78rem;
  white-space: nowrap;
  cursor: default;
}
.xp-chip-label { letter-spacing: 0.08em; font-weight: 800; font-size: 0.66rem; }

/* ---------- Display type upgrade ---------- */
h1.stage-title, .welcome-title {
  font-family: 'Space Grotesk', var(--font-display);
  letter-spacing: -0.02em;
}
.stage-hero { border-top: 3px solid var(--primary-accent); }

/* ---------- Responsive ---------- */
@media (max-width: 1100px) {
  .toc-rail { position: static; float: none; width: auto; margin: 0 0 1.5rem; max-height: none; }
}
@media (max-width: 900px) {
  .match-grid { grid-template-columns: 1fr; }
  .lesson-head-row { flex-wrap: wrap; }
  .xp-chip { display: none; }
}
@media (max-width: 600px) {
  .lab-bench { padding: 0.9rem 0.95rem 1rem; }
  .bench-xp { display: none; }
}

/* ---------- Reduced motion ---------- */
@media (prefers-reduced-motion: reduce) {
  .bench-led { animation: none; }
  .match-item.shake { animation: none; }
  .toc-rail, .lab-bench, .sort-tile { transition: none; }
}

/* ============================================================
   Feature: Hello World intro + Prompt Battle Lab
   ============================================================ */

/* ---------- Sidebar quick nav ---------- */
.sidebar-quick-nav {
  margin-top: 1.1rem;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.5rem;
}
body.minimal-roadmap .sidebar-quick-nav { display: none !important; }
.sidebar-quick-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.62rem 0.5rem;
  background: rgba(99, 102, 241, 0.08);
  border: 1px solid rgba(99, 102, 241, 0.28);
  border-radius: var(--radius-md);
  color: var(--text-main);
  font-family: var(--font-body);
  font-size: 0.82rem;
  font-weight: 600;
  cursor: pointer;
  transition: border-color var(--transition-fast), background var(--transition-fast), transform var(--transition-fast), box-shadow var(--transition-fast);
}
.sidebar-quick-btn:hover {
  background: rgba(99, 102, 241, 0.16);
  border-color: var(--border-glow);
  box-shadow: 0 0 18px rgba(99, 102, 241, 0.18);
  transform: translateY(-1px);
}
.quick-btn-icon { font-size: 1rem; line-height: 1; }
.quick-btn-label { white-space: nowrap; }

/* ---------- Shared modal backdrop ---------- */
.hello-modal-backdrop, .battle-modal-backdrop {
  position: fixed;
  inset: 0;
  z-index: 6000;
  background: rgba(5, 8, 16, 0.82);
  backdrop-filter: blur(10px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s ease;
}
.hello-modal-backdrop[hidden], .battle-modal-backdrop[hidden] { display: none; }
.hello-modal-backdrop.open, .battle-modal-backdrop.open { opacity: 1; pointer-events: auto; }

/* ---------- Hello World modal ---------- */
.hello-modal-card {
  position: relative;
  width: 100%;
  max-width: 620px;
  max-height: 90vh;
  overflow-y: auto;
  background: linear-gradient(160deg, #131A2A 0%, #0E1424 100%);
  border: 1px solid var(--border-glow);
  border-radius: 20px;
  box-shadow: 0 30px 80px rgba(0, 0, 0, 0.6), 0 0 40px rgba(99, 102, 241, 0.12);
  padding: 2.2rem 2.2rem 2rem;
  transform: translateY(14px) scale(0.98);
  transition: transform 0.28s cubic-bezier(0.34, 1.3, 0.64, 1);
}
.hello-modal-backdrop.open .hello-modal-card { transform: translateY(0) scale(1); }
.hello-close-btn, .battle-close-btn {
  position: absolute;
  top: 0.9rem;
  right: 0.9rem;
  width: 32px;
  height: 32px;
  border-radius: var(--radius-full);
  border: 1px solid var(--border-color);
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-muted);
  font-size: 1rem;
  line-height: 1;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition-fast);
}
.hello-close-btn:hover, .battle-close-btn:hover { color: var(--text-main); border-color: var(--border-glow); background: rgba(99, 102, 241, 0.15); }
.hello-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-code);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  color: var(--secondary-accent);
  background: rgba(6, 182, 212, 0.1);
  border: 1px solid rgba(6, 182, 212, 0.3);
  border-radius: var(--radius-full);
  padding: 0.32rem 0.85rem;
  margin-bottom: 1rem;
}
.hello-title {
  font-family: "Space Grotesk", var(--font-display);
  font-size: 2rem;
  letter-spacing: -0.02em;
  margin: 0 0 0.5rem;
  background: linear-gradient(90deg, #F9FAFB 0%, #A5B4FC 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}
.hello-kicker {
  color: var(--text-muted);
  font-size: 0.95rem;
  margin: 0 0 1.4rem;
  font-style: italic;
}

/* Terminal window */
.hello-terminal {
  border-radius: 14px;
  overflow: hidden;
  border: 1px solid rgba(255, 255, 255, 0.1);
  background: #0A0E1A;
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.45);
  margin-bottom: 1.6rem;
}
.terminal-bar {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.6rem 0.9rem;
  background: rgba(255, 255, 255, 0.04);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}
.terminal-dot { width: 11px; height: 11px; border-radius: 50%; display: inline-block; }
.terminal-dot-red { background: #FF5F57; }
.terminal-dot-yellow { background: #FEBC2E; }
.terminal-dot-green { background: #28C840; }
.terminal-title {
  margin-left: 0.5rem;
  font-family: var(--font-code);
  font-size: 0.72rem;
  color: var(--text-dim);
  letter-spacing: 0.04em;
}
.terminal-body {
  padding: 1rem 1.1rem 1rem 0;
  min-height: 232px;
  font-family: var(--font-code);
  font-size: 0.83rem;
  line-height: 1.75;
}
.terminal-line { display: flex; align-items: baseline; }
.terminal-line-no {
  flex: 0 0 2.4rem;
  text-align: right;
  padding-right: 1rem;
  color: #3D4A63;
  user-select: none;
}
.terminal-line-text { color: #D6E1F5; white-space: pre-wrap; word-break: break-word; }
.term-comment { color: #5B8C6A; font-style: italic; }
.typewriter-caret {
  display: inline-block;
  width: 8px;
  height: 1.05em;
  margin-left: 2px;
  vertical-align: text-bottom;
  background: var(--secondary-accent);
  box-shadow: 0 0 8px rgba(6, 182, 212, 0.8);
  animation: caret-blink 0.9s steps(1) infinite;
}
@keyframes caret-blink { 0%, 49% { opacity: 1; } 50%, 100% { opacity: 0; } }

/* Story copy */
.hello-story p {
  color: var(--text-muted);
  font-size: 0.92rem;
  line-height: 1.75;
  margin: 0 0 0.85rem;
}
.hello-story strong { color: var(--text-main); }
.hello-story em { color: var(--secondary-accent); }
.hello-cta {
  width: 100%;
  margin-top: 0.4rem;
  padding: 0.85rem 1.2rem;
  border: none;
  border-radius: var(--radius-md);
  background: linear-gradient(90deg, var(--primary-accent), var(--secondary-accent));
  color: #FFFFFF;
  font-family: var(--font-body);
  font-size: 0.95rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), filter var(--transition-fast);
}
.hello-cta:hover { transform: translateY(-1px); box-shadow: 0 10px 30px rgba(99, 102, 241, 0.35); filter: brightness(1.08); }
.hello-footnote {
  margin-top: 1rem;
  text-align: center;
  color: var(--text-dim);
  font-size: 0.8rem;
}

/* ---------- Prompt Battle Lab modal ---------- */
.battle-modal-card {
  position: relative;
  width: 100%;
  max-width: 640px;
  max-height: 90vh;
  overflow-y: auto;
  background: linear-gradient(160deg, #131A2A 0%, #0E1424 100%);
  border: 1px solid var(--border-glow);
  border-radius: 20px;
  box-shadow: 0 30px 80px rgba(0, 0, 0, 0.6), 0 0 40px rgba(99, 102, 241, 0.12);
  padding: 2.2rem 2.2rem 1.6rem;
  transform: translateY(14px) scale(0.98);
  transition: transform 0.28s cubic-bezier(0.34, 1.3, 0.64, 1);
}
.battle-modal-backdrop.open .battle-modal-card { transform: translateY(0) scale(1); }
.battle-header { text-align: center; margin-bottom: 1.4rem; }
.battle-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-code);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  color: var(--warning-accent);
  background: rgba(245, 158, 11, 0.1);
  border: 1px solid rgba(245, 158, 11, 0.3);
  border-radius: var(--radius-full);
  padding: 0.32rem 0.85rem;
  margin-bottom: 0.8rem;
}
.battle-title {
  font-family: "Space Grotesk", var(--font-display);
  font-size: 1.7rem;
  letter-spacing: -0.02em;
  margin: 0 0 0.4rem;
}
.battle-intro { color: var(--text-muted); font-size: 0.92rem; margin: 0; }

.battle-task {
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-left: 3px solid var(--primary-accent);
  border-radius: var(--radius-md);
  padding: 1rem 1.15rem;
  margin-bottom: 1.1rem;
}
.battle-task-label {
  font-family: var(--font-code);
  font-size: 0.66rem;
  font-weight: 700;
  letter-spacing: 0.18em;
  color: var(--secondary-accent);
  display: block;
  margin-bottom: 0.35rem;
}
.battle-task-title { font-weight: 700; color: var(--text-main); margin-bottom: 0.3rem; }
.battle-task-detail { color: var(--text-muted); font-size: 0.86rem; }

.battle-options { display: grid; gap: 0.7rem; margin-bottom: 1.1rem; }
.battle-option {
  display: flex;
  align-items: flex-start;
  gap: 0.85rem;
  text-align: left;
  padding: 0.95rem 1.1rem;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-md);
  color: var(--text-main);
  font-family: var(--font-body);
  font-size: 0.9rem;
  line-height: 1.55;
  cursor: pointer;
  transition: border-color var(--transition-fast), background var(--transition-fast), transform var(--transition-fast), box-shadow var(--transition-fast);
}
.battle-option:hover:not(.locked) {
  border-color: var(--border-glow);
  background: rgba(99, 102, 241, 0.1);
  transform: translateY(-1px);
}
.battle-option-tag {
  flex: 0 0 auto;
  width: 28px;
  height: 28px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-code);
  font-weight: 700;
  font-size: 0.8rem;
  background: rgba(99, 102, 241, 0.18);
  border: 1px solid rgba(99, 102, 241, 0.35);
  color: #A5B4FC;
}
.battle-option.is-correct {
  border-color: var(--success-accent);
  background: rgba(16, 185, 129, 0.12);
  box-shadow: 0 0 20px rgba(16, 185, 129, 0.15);
}
.battle-option.is-correct .battle-option-tag { background: var(--success-accent); border-color: var(--success-accent); color: #04120C; }
.battle-option.is-wrong {
  border-color: #F87171;
  background: rgba(248, 113, 113, 0.1);
  box-shadow: 0 0 20px rgba(248, 113, 113, 0.12);
}
.battle-option.is-wrong .battle-option-tag { background: #F87171; border-color: #F87171; color: #1C0505; }
.battle-option.is-good { border-color: rgba(16, 185, 129, 0.55); opacity: 0.85; }
.battle-option.locked { cursor: default; }

.battle-reason {
  border-radius: var(--radius-md);
  padding: 1rem 1.15rem;
  animation: reason-in 0.3s ease both;
}
@keyframes reason-in { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }
.battle-reason.good { background: rgba(16, 185, 129, 0.1); border: 1px solid rgba(16, 185, 129, 0.35); }
.battle-reason.bad { background: rgba(248, 113, 113, 0.08); border: 1px solid rgba(248, 113, 113, 0.3); }
.battle-reason-head { font-weight: 700; margin-bottom: 0.5rem; }
.battle-reason.good .battle-reason-head { color: #34D399; }
.battle-reason.bad .battle-reason-head { color: #F87171; }
.battle-reason-why { color: var(--text-muted); font-size: 0.88rem; line-height: 1.6; margin-bottom: 0.6rem; }
.battle-reason-tip {
  font-size: 0.82rem;
  color: var(--text-main);
  background: rgba(255, 255, 255, 0.05);
  border-radius: var(--radius-sm);
  padding: 0.6rem 0.75rem;
  line-height: 1.55;
}
.battle-reason-tip strong { color: var(--secondary-accent); }

.battle-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 0.4rem;
}
.battle-progress { flex: 1; min-width: 0; }
.battle-progress-label {
  font-family: var(--font-code);
  font-size: 0.72rem;
  color: var(--text-muted);
  display: block;
  margin-bottom: 0.35rem;
}
.battle-progress-track { height: 6px; border-radius: var(--radius-full); background: rgba(255, 255, 255, 0.08); overflow: hidden; }
.battle-progress-fill {
  display: block;
  height: 100%;
  width: 0%;
  border-radius: var(--radius-full);
  background: linear-gradient(90deg, var(--primary-accent), var(--secondary-accent));
  transition: width 0.35s ease;
}
.battle-nav { display: flex; gap: 0.5rem; }
.battle-nav-btn {
  padding: 0.55rem 1rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-main);
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition-fast);
}
.battle-nav-btn:disabled { opacity: 0.4; cursor: not-allowed; }
.battle-nav-btn:hover:not(:disabled) { border-color: var(--border-glow); background: rgba(99, 102, 241, 0.15); }
.battle-nav-next { background: linear-gradient(90deg, var(--primary-accent), var(--secondary-accent)); border: none; color: #FFFFFF; }
.battle-nav-next:hover:not(:disabled) { filter: brightness(1.1); }

/* ---------- Responsive ---------- */
@media (max-width: 560px) {
  .hello-modal-card, .battle-modal-card { padding: 1.6rem 1.3rem 1.4rem; }
  .hello-title { font-size: 1.6rem; }
  .battle-title { font-size: 1.4rem; }
  .battle-footer { flex-direction: column; align-items: stretch; }
  .battle-nav { justify-content: flex-end; }
  .sidebar-quick-nav { grid-template-columns: 1fr; }
}

/* ---------- Reduced motion ---------- */
@media (prefers-reduced-motion: reduce) {
  .typewriter-caret { animation: none; }
  .hello-modal-card, .battle-modal-card { transition: none; }
  .battle-reason { animation: none; }
  .sidebar-quick-btn { transition: none; }
}

/* ---------- Course-opening origin hero (Hello World) ---------- */
.origin-hero {
  position: relative;
  margin: 0 0 2.4rem;
  padding: 2.2rem 2.2rem 1.8rem;
  border-radius: 20px;
  background: linear-gradient(160deg, rgba(19, 26, 42, 0.92) 0%, rgba(14, 20, 36, 0.96) 100%);
  border: 1px solid var(--border-glow);
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.4), 0 0 40px rgba(99, 102, 241, 0.08);
  overflow: hidden;
}
.origin-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background: radial-gradient(600px 240px at 15% 0%, rgba(99, 102, 241, 0.16), transparent 70%),
              radial-gradient(500px 200px at 90% 100%, rgba(6, 182, 212, 0.1), transparent 70%);
}
.origin-hero > * { position: relative; }
.origin-hero .hello-cta { margin-top: 0.4rem; }
@media (max-width: 560px) {
  .origin-hero { padding: 1.6rem 1.3rem 1.4rem; }
}