:root {
  --primary: #4F46E5;
  --primary-light: #6366F1;
  --secondary: #EC4899;
  --accent-yellow: #F59E0B;
  --accent-green: #10B981;
  --accent-cyan: #06B6D4;
  --accent-orange: #F97316;
  
  --bg-gradient: linear-gradient(135deg, #F0F4FF 0%, #E6EDFF 40%, #FDF2F8 100%);
  --card-bg: #FFFFFF;
  --card-border: #E2E8F0;
  --text-dark: #0F172A;
  --text-muted: #64748B;
  
  --shadow-sm: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  
  --radius-sm: 12px;
  --radius-md: 18px;
  --radius-lg: 24px;
  --radius-pill: 9999px;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  user-select: none;
  -webkit-user-select: none;
}

body {
  font-family: 'Fredoka', 'Nunito', system-ui, sans-serif;
  background: var(--bg-gradient);
  color: var(--text-dark);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
}

/* ================= AUTO-HIDING NAVBAR (HOVER TO REVEAL) ================= */
.main-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background: #ffffff;
  padding: 10px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  box-shadow: 0 6px 20px rgba(79, 70, 229, 0.15);
  border-bottom: 3px solid #E0E7FF;
  z-index: 100;
  transform: translateY(-84%);
  opacity: 0.2;
  transition: transform 0.28s cubic-bezier(0.16, 1, 0.3, 1), opacity 0.28s ease;
  flex-wrap: wrap;
  gap: 12px;
}

/* Hover near top reveals header (NO :focus-within so it retracts immediately on mouse leave) */
.main-header:hover {
  transform: translateY(0);
  opacity: 1;
}

/* Force collapse when user clicks any navbar button/control */
.main-header.collapsed {
  transform: translateY(-84%) !important;
  opacity: 0.2 !important;
}

.main-header::after {
  content: '✨ Menu & Quizzes (Hover Here)';
  position: absolute;
  bottom: -24px;
  left: 50%;
  transform: translateX(-50%);
  background: rgba(79, 70, 229, 0.92);
  backdrop-filter: blur(4px);
  color: #FFFFFF;
  font-size: 0.74rem;
  font-weight: 800;
  padding: 3px 16px;
  border-radius: 0 0 14px 14px;
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.12);
  pointer-events: auto;
  cursor: pointer;
  transition: opacity 0.2s ease;
}

.main-header:hover::after {
  opacity: 0;
  pointer-events: none;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand-logo {
  font-size: 2rem;
  background: #EEF2FF;
  padding: 6px 12px;
  border-radius: var(--radius-md);
  border: 2px solid #C7D2FE;
}

.brand-text h1 {
  font-size: 1.35rem;
  font-weight: 700;
  color: #312E81;
  line-height: 1.2;
}

.studio-badge {
  display: inline-block;
  background: linear-gradient(90deg, #4338CA, #7C3AED);
  color: #FFFFFF;
  font-size: 0.75rem;
  font-weight: 800;
  padding: 2px 10px;
  border-radius: var(--radius-pill);
  letter-spacing: 0.5px;
  text-transform: uppercase;
}

.lesson-switcher {
  display: flex;
  align-items: center;
  gap: 6px;
  background: #F8FAFC;
  padding: 4px 10px;
  border-radius: var(--radius-pill);
  border: 1px solid #CBD5E1;
  flex-wrap: wrap;
}

.lesson-label {
  font-size: 0.72rem;
  font-weight: 800;
  color: var(--text-muted);
  text-transform: uppercase;
  margin-right: 2px;
}

.lesson-chip {
  font-size: 0.82rem;
  font-weight: 800;
  padding: 5px 12px;
  border-radius: var(--radius-pill);
  text-decoration: none;
  transition: all 0.15s ease;
  white-space: nowrap;
}

.lesson-chip.active {
  background: var(--primary);
  color: #FFFFFF;
  box-shadow: 0 2px 6px rgba(79, 70, 229, 0.25);
}

.lesson-chip.link {
  color: #334155;
  background: #FFFFFF;
  border: 1px solid #CBD5E1;
}

.lesson-chip.link:hover {
  background: #EEF2FF;
  border-color: var(--primary-light);
  color: var(--primary);
  transform: translateY(-1px);
}

.lesson-chip.home {
  color: #78350F;
  background: #FEF3C7;
  border: 1px solid #FDE68A;
  font-weight: 800;
}

.lesson-chip.home:hover {
  background: #FDE68A;
  border-color: #F59E0B;
  color: #92400E;
  transform: translateY(-1px);
}

.nav-controls {
  display: flex;
  align-items: center;
  gap: 10px;
}

.mode-tabs {
  display: flex;
  background: #F1F5F9;
  padding: 4px;
  border-radius: var(--radius-pill);
  gap: 4px;
}

.tab-btn {
  border: none;
  background: transparent;
  padding: 8px 18px;
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-muted);
  border-radius: var(--radius-pill);
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  display: flex;
  align-items: center;
  gap: 6px;
}

.tab-btn.active {
  background: var(--primary);
  color: #FFFFFF;
  box-shadow: 0 4px 10px rgba(79, 70, 229, 0.3);
}

.icon-toggle-btn {
  background: #F8FAFC;
  border: 2px solid #CBD5E1;
  font-size: 1.2rem;
  padding: 7px 12px;
  border-radius: var(--radius-pill);
  cursor: pointer;
  transition: transform 0.1s;
}

.icon-toggle-btn:active {
  transform: scale(0.92);
}

/* App Container */
.app-container {
  flex: 1;
  max-width: 1560px;
  width: 100%;
  margin: 16px auto 0 auto;
  padding: 8px 18px;
  display: flex;
  flex-direction: column;
}

.view-panel {
  display: none;
  animation: fadeIn 0.25s ease;
}

.view-panel.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Shapes Carousel */
.shapes-shelf-wrapper {
  margin-bottom: 10px;
}

.shapes-shelf {
  display: flex;
  gap: 10px;
  padding: 2px 2px 8px 2px;
  overflow-x: auto;
  scrollbar-width: thin;
  scrollbar-color: #CBD5E1 transparent;
}

.shapes-shelf::-webkit-scrollbar {
  height: 6px;
}

.shapes-shelf::-webkit-scrollbar-thumb {
  background: #CBD5E1;
  border-radius: 10px;
}

.shape-chip {
  flex: 0 0 auto;
  background: var(--card-bg);
  border: 3px solid #E2E8F0;
  border-radius: var(--radius-md);
  padding: 7px 15px;
  display: flex;
  align-items: center;
  gap: 8px;
  cursor: pointer;
  transition: all 0.18s ease;
  box-shadow: 0 3px 0px #CBD5E1;
}

.shape-chip:hover {
  transform: translateY(-2px);
  border-color: var(--primary-light);
}

.shape-chip.active {
  background: linear-gradient(135deg, #EEF2FF 0%, #FFFFFF 100%);
  border-color: var(--primary);
  box-shadow: 0 5px 0px var(--primary);
  transform: translateY(-3px);
}

.shape-chip .chip-icon {
  font-size: 1.35rem;
}

.shape-chip .chip-name {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-dark);
}

/* Stage Layout */
.stage-container {
  display: grid;
  grid-template-columns: 2.6fr 1fr;
  gap: 16px;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  align-items: start;
}

.stage-container.theater-mode {
  grid-template-columns: 1fr;
}

.stage-container.theater-mode .shape-details-panel {
  display: none;
}

@media (max-width: 1024px) {
  .stage-container {
    grid-template-columns: 1fr;
  }
}

/* ================= 3D CANVAS WRAPPER ================= */
.canvas-wrapper {
  position: relative;
  background: #FFFFFF;
  border: 4px solid #FFFFFF;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  height: calc(100vh - 105px);
  min-height: 640px;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* 3D Viewport: Completely Unobstructed Area */
.canvas-viewport {
  flex: 1;
  position: relative;
  width: 100%;
  min-height: 0;
  background: #F8FAFC;
  overflow: hidden;
  transition: background 0.3s ease;
}

#webglCanvas {
  width: 100%;
  height: 100%;
  display: block;
  cursor: grab;
}

#webglCanvas:active {
  cursor: grabbing;
}

/* Top Canvas HUD Bar */
.canvas-top-bar {
  position: absolute;
  top: 14px;
  left: 14px;
  right: 14px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 10;
  pointer-events: none;
  flex-wrap: wrap;
  gap: 8px;
}

.canvas-top-bar > * {
  pointer-events: auto;
}

/* Display Mode Switch */
.display-mode-switch {
  display: flex;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  padding: 4px;
  border-radius: var(--radius-pill);
  border: 2px solid #CBD5E1;
  box-shadow: var(--shadow-md);
  gap: 4px;
}

.mode-pill-btn {
  border: none;
  background: transparent;
  padding: 6px 15px;
  border-radius: var(--radius-pill);
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 800;
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.15s ease;
}

.mode-pill-btn.active {
  background: linear-gradient(135deg, #F97316 0%, #EA580C 100%);
  color: #FFFFFF;
  box-shadow: 0 2px 6px rgba(234, 88, 12, 0.35);
}

.hud-btn {
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  border: 2px solid #CBD5E1;
  padding: 6px 14px;
  border-radius: var(--radius-pill);
  font-family: inherit;
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--text-dark);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  box-shadow: var(--shadow-sm);
  transition: all 0.15s ease;
}

.hud-btn:hover {
  border-color: var(--primary-light);
  transform: scale(1.03);
}

.hud-btn.active {
  background: var(--primary);
  color: #FFFFFF;
  border-color: var(--primary);
}

/* Explode Slider Card (Top Left Corner) */
.canvas-slider-card {
  position: absolute;
  top: 64px;
  left: 14px;
  background: rgba(255, 255, 255, 0.94);
  backdrop-filter: blur(8px);
  border: 2px solid #CBD5E1;
  padding: 8px 12px;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: 5px;
  z-index: 10;
  min-width: 190px;
}

.slider-title-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-dark);
}

.slider-val {
  color: var(--primary);
  font-weight: 800;
}

input[type="range"] {
  accent-color: var(--primary);
  cursor: pointer;
  width: 100%;
}

/* Color Customization Stack (Top Right Corner) */
.canvas-right-stack {
  position: absolute;
  top: 64px;
  right: 14px;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 6px;
  z-index: 10;
}

.palette-toggle-btn {
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  border: 2px solid #CBD5E1;
  padding: 5px 12px;
  border-radius: var(--radius-pill);
  box-shadow: var(--shadow-sm);
  display: flex;
  align-items: center;
  gap: 6px;
  font-family: inherit;
  font-size: 0.8rem;
  font-weight: 800;
  color: var(--text-dark);
  cursor: pointer;
  transition: all 0.15s ease;
}

.palette-toggle-btn:hover {
  background: #EEF2FF;
  border-color: var(--primary-light);
  transform: translateY(-1px);
}

.palette-toggle-arrow {
  font-size: 0.72rem;
  color: var(--text-muted);
}

.palette-content-panel {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 6px;
  transition: all 0.2s ease;
}

.palette-content-panel.collapsed {
  display: none;
}

.canvas-palette-card {
  background: rgba(255, 255, 255, 0.94);
  backdrop-filter: blur(8px);
  border: 2px solid #CBD5E1;
  padding: 6px 10px;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  display: flex;
  align-items: center;
  gap: 8px;
}

.palette-label {
  font-size: 0.76rem;
  font-weight: 800;
  color: var(--text-dark);
}

.color-dots {
  display: flex;
  gap: 5px;
}

.color-dot, .bg-swatch {
  width: 18px;
  height: 18px;
  border-radius: 50%;
  cursor: pointer;
  border: 2px solid #FFFFFF;
  box-shadow: 0 0 0 1px #CBD5E1;
  transition: transform 0.15s ease;
}

.color-dot:hover, .bg-swatch:hover {
  transform: scale(1.25);
}

.color-dot.active, .bg-swatch.active {
  box-shadow: 0 0 0 3px #1E1B4B;
  transform: scale(1.15);
}

/* Drag Hint */
.drag-hint {
  position: absolute;
  bottom: 10px;
  left: 50%;
  transform: translateX(-50%);
  background: rgba(15, 23, 42, 0.65);
  backdrop-filter: blur(4px);
  color: #FFFFFF;
  padding: 4px 12px;
  border-radius: var(--radius-pill);
  font-size: 0.76rem;
  font-weight: 600;
  pointer-events: none;
  white-space: nowrap;
}

/* ================= DEDICATED BOTTOM TOOLBAR STRIP ================= */
.canvas-bottom-bar {
  flex: 0 0 auto;
  background: #FFFFFF;
  border-top: 2px solid #E2E8F0;
  padding: 8px 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  flex-wrap: wrap;
  z-index: 20;
}

.bar-btn {
  background: #F8FAFC;
  border: 2px solid #CBD5E1;
  padding: 6px 14px;
  border-radius: var(--radius-pill);
  font-family: inherit;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--text-dark);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: all 0.15s ease;
}

.bar-btn:hover {
  background: #EEF2FF;
  border-color: var(--primary-light);
  transform: translateY(-1px);
}

.bar-btn.active {
  background: var(--primary);
  color: #FFFFFF;
  border-color: #3730A3;
}

.bar-btn.active b {
  color: #A7F3D0;
}

/* Details Panel (Matching Height & Scrollable) */
.shape-details-panel {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 18px;
  border: 3px solid #E0E7FF;
  box-shadow: var(--shadow-md);
  display: flex;
  flex-direction: column;
  gap: 12px;
  height: calc(100vh - 105px);
  min-height: 640px;
  overflow-y: auto;
}

.panel-header {
  display: flex;
  align-items: center;
  gap: 12px;
}

.shape-badge-icon {
  font-size: 2.2rem;
  background: #EEF2FF;
  padding: 6px 12px;
  border-radius: var(--radius-md);
  border: 2px solid #C7D2FE;
}

.panel-header h2 {
  font-size: 1.55rem;
  font-weight: 700;
  color: #1E1B4B;
}

.shape-subtitle {
  font-size: 0.88rem;
  color: var(--text-muted);
  font-weight: 600;
}

/* Properties Grid */
.properties-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}

.prop-card {
  background: #F8FAFC;
  border-radius: var(--radius-md);
  padding: 10px 8px;
  text-align: center;
  border: 3px solid #E2E8F0;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
  box-shadow: 0 3px 0 #CBD5E1;
}

.prop-card:hover {
  transform: translateY(-2px);
}

.prop-card.face-card {
  border-color: #93C5FD;
  background: #EFF6FF;
  box-shadow: 0 3px 0 #93C5FD;
}

.prop-card.edge-card {
  border-color: #FDE047;
  background: #FEFCE8;
  box-shadow: 0 3px 0 #FACC15;
}

.prop-card.vert-card {
  border-color: #FCA5A5;
  background: #FEF2F2;
  box-shadow: 0 3px 0 #F87171;
}

.prop-card .prop-icon {
  font-size: 1.35rem;
}

.prop-info {
  display: flex;
  flex-direction: column;
}

.prop-label {
  font-size: 0.76rem;
  font-weight: 800;
  color: var(--text-muted);
  text-transform: uppercase;
}

.prop-number {
  font-size: 1.8rem;
  font-weight: 800;
  color: #0F172A;
  line-height: 1.1;
  margin: 2px 0;
}

.prop-desc {
  font-size: 0.72rem;
  color: var(--text-muted);
  font-weight: 600;
}

/* Surface Type Breakdown (Flat vs Curved) */
.surfaces-type-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.surface-type-card {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 10px;
  border-radius: var(--radius-md);
  border: 1px solid #E2E8F0;
  background: #F8FAFC;
}

.surface-type-card.flat {
  background: #F0FDF4;
  border-color: #BBF7D0;
}

.surface-type-card.curved {
  background: #EFF6FF;
  border-color: #BFDBFE;
}

.surface-icon {
  font-size: 1.25rem;
}

.surface-info {
  display: flex;
  flex-direction: column;
}

.surface-count {
  font-size: 1.1rem;
  font-weight: 800;
  color: #1E293B;
  line-height: 1.1;
}

.surface-label {
  font-size: 0.68rem;
  font-weight: 700;
  color: var(--text-muted);
  text-transform: uppercase;
}

/* Face Shapes Card */
.face-shapes-card {
  background: #F8FAFC;
  border: 1.5px solid #E2E8F0;
  border-radius: var(--radius-md);
  padding: 10px 12px;
}

.face-shapes-card h3 {
  font-size: 0.82rem;
  color: #334155;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 4px;
}

.face-shapes-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.face-shape-item {
  display: flex;
  align-items: center;
  gap: 8px;
  background: #FFFFFF;
  border: 1.5px solid #CBD5E1;
  border-radius: var(--radius-sm);
  padding: 4px 8px;
  box-shadow: 0 1px 3px rgba(0,0,0,0.05);
}

.face-shape-svg {
  width: 24px;
  height: 24px;
  display: block;
}

.face-shape-text {
  font-size: 0.8rem;
  font-weight: 700;
  color: #1E293B;
}

.face-shape-count-badge {
  background: #EEF2FF;
  color: #4F46E5;
  font-weight: 800;
  font-size: 0.75rem;
  padding: 1px 6px;
  border-radius: var(--radius-pill);
}

/* Real Examples List */
.real-examples-card {
  background: #FAF5FF;
  border: 2px dashed #C084FC;
  border-radius: var(--radius-md);
  padding: 12px;
}

.real-examples-card h3 {
  font-size: 0.88rem;
  color: #6B21A8;
  margin-bottom: 8px;
}

.examples-list {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.example-tag {
  background: #FFFFFF;
  border: 2px solid #E9D5FF;
  border-radius: var(--radius-pill);
  padding: 4px 10px;
  font-size: 0.82rem;
  font-weight: 700;
  color: #581C87;
  display: flex;
  align-items: center;
  gap: 4px;
}

/* Fun Tip */
.fun-tip-box {
  background: #ECFDF5;
  border-left: 5px solid var(--accent-green);
  border-radius: var(--radius-sm);
  padding: 10px 12px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.tip-bulb {
  font-size: 1.3rem;
}

.tip-text {
  font-size: 0.85rem;
  font-weight: 600;
  color: #065F46;
}

/* ================= QUIZ MODE ================= */
.quiz-container {
  max-width: 820px;
  margin: 12px auto;
  width: 100%;
}

.quiz-card {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 28px 24px;
  border: 4px solid #E0E7FF;
  box-shadow: var(--shadow-lg);
}

.quiz-card.hidden {
  display: none;
}

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

.quiz-hero-icon {
  font-size: 3.2rem;
  margin-bottom: 10px;
}

.quiz-card h2 {
  font-size: 1.85rem;
  color: #312E81;
  margin-bottom: 8px;
}

.quiz-card p {
  color: var(--text-muted);
  font-size: 1.05rem;
  margin-bottom: 22px;
}

/* Quiz Selection Grid */
.quiz-selection-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-top: 10px;
}

@media (max-width: 650px) {
  .quiz-selection-grid {
    grid-template-columns: 1fr;
  }
}

.quiz-level-card {
  background: #F8FAFC;
  border: 3px solid #CBD5E1;
  border-radius: var(--radius-md);
  padding: 20px 16px;
  text-align: left;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
  box-shadow: 0 4px 0 #CBD5E1;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.quiz-level-card:hover {
  transform: translateY(-4px);
  border-color: var(--primary);
  background: #EEF2FF;
  box-shadow: 0 8px 0 var(--primary);
}

.quiz-level-card .level-icon {
  font-size: 2.2rem;
  margin-bottom: 4px;
}

.quiz-level-card h3 {
  font-size: 1.25rem;
  color: #1E1B4B;
  font-weight: 800;
}

.quiz-level-card p {
  font-size: 0.9rem;
  color: var(--text-muted);
  margin-bottom: 8px;
  line-height: 1.3;
}

.quiz-level-card .level-badge {
  align-self: flex-start;
  background: #E0E7FF;
  color: #4338CA;
  font-size: 0.78rem;
  font-weight: 800;
  padding: 3px 10px;
  border-radius: var(--radius-pill);
}

/* Active Quiz Layout */
.quiz-header-status {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
  flex-wrap: wrap;
  gap: 8px;
}

.quiz-header-left {
  display: flex;
  align-items: center;
  gap: 12px;
}

.quiz-level-indicator {
  font-weight: 800;
  font-size: 1.15rem;
  color: #312E81;
}

.quiz-header-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

.quiz-progress-text {
  font-weight: 800;
  font-size: 1rem;
  color: #4338CA;
}

.quiz-score-badge {
  background: #FEF3C7;
  border: 2px solid #FCD34D;
  padding: 4px 12px;
  border-radius: var(--radius-pill);
  font-weight: 800;
  color: #B45309;
}

.quiz-progress-bar {
  background: #E2E8F0;
  height: 12px;
  border-radius: var(--radius-pill);
  overflow: hidden;
  margin-bottom: 22px;
}

.progress-fill {
  background: linear-gradient(90deg, #6366F1, #10B981);
  height: 100%;
  border-radius: var(--radius-pill);
  transition: width 0.3s ease;
}

.quiz-question-body {
  text-align: center;
  margin-bottom: 22px;
}

.question-illustration {
  font-size: 3.8rem;
  margin-bottom: 12px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 24px;
  background: #F8FAFC;
  border: 3px solid #E2E8F0;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  min-height: 96px;
}

.question-illustration svg {
  display: block;
  filter: drop-shadow(0 4px 8px rgba(0, 0, 0, 0.12));
}

.quiz-question-body h3 {
  font-size: 1.45rem;
  font-weight: 700;
  color: #1E293B;
  line-height: 1.35;
}

.quiz-options-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
  margin-bottom: 16px;
}

@media (max-width: 580px) {
  .quiz-options-grid {
    grid-template-columns: 1fr;
  }
}

.quiz-opt-btn {
  background: #FFFFFF;
  border: 3px solid #CBD5E1;
  padding: 16px;
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 1.15rem;
  font-weight: 800;
  color: #1E293B;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  box-shadow: 0 4px 0 #94A3B8;
  transition: all 0.15s ease;
}

.quiz-opt-btn:hover {
  background: #F8FAFC;
  border-color: #6366F1;
  transform: translateY(-2px);
  box-shadow: 0 6px 0 #6366F1;
}

.quiz-opt-btn.correct {
  background: #D1FAE5 !important;
  border-color: #10B981 !important;
  color: #065F46 !important;
  box-shadow: 0 4px 0 #059669 !important;
}

.quiz-opt-btn.wrong {
  background: #FEE2E2 !important;
  border-color: #EF4444 !important;
  color: #991B1B !important;
  box-shadow: 0 4px 0 #DC2626 !important;
}

.quiz-feedback {
  padding: 12px;
  border-radius: var(--radius-md);
  font-size: 1.05rem;
  font-weight: 800;
  text-align: center;
  animation: popIn 0.25s ease;
}

@keyframes popIn {
  0% { transform: scale(0.9); opacity: 0; }
  100% { transform: scale(1); opacity: 1; }
}

.quiz-feedback.correct {
  background: #D1FAE5;
  color: #065F46;
  border: 2px solid #10B981;
}

.quiz-feedback.wrong {
  background: #FEE2E2;
  color: #991B1B;
  border: 2px solid #EF4444;
}

.quiz-feedback.hidden {
  display: none;
}

/* Next Question Button */
.quiz-nav-row {
  margin-top: 20px;
  display: flex;
  justify-content: center;
}

.btn-next-question {
  background: linear-gradient(135deg, #4F46E5, #7C3AED);
  color: #FFFFFF;
  font-family: inherit;
  font-size: 1.15rem;
  font-weight: 800;
  padding: 12px 34px;
  border-radius: var(--radius-pill);
  border: 2px solid #C7D2FE;
  box-shadow: 0 6px 18px rgba(79, 70, 229, 0.35);
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
  display: inline-flex;
  align-items: center;
  gap: 8px;
  animation: popIn 0.25s ease;
}

.btn-next-question:hover {
  transform: translateY(-3px) scale(1.03);
  box-shadow: 0 10px 24px rgba(79, 70, 229, 0.45);
  background: linear-gradient(135deg, #4338CA, #6D28D9);
}

.btn-next-question:active {
  transform: translateY(0) scale(0.98);
}

.btn-next-question.hidden {
  display: none;
}

/* Completion End Card */
.trophy-bounce {
  font-size: 4.5rem;
  margin-bottom: 12px;
  animation: bounce 1.5s infinite;
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-12px); }
}

.final-score-box {
  background: #FEF3C7;
  border: 3px solid #FCD34D;
  border-radius: var(--radius-lg);
  padding: 16px;
  margin: 20px auto 26px auto;
  max-width: 320px;
}

.stars-row {
  font-size: 2.2rem;
  margin-bottom: 6px;
}

.score-display {
  font-size: 1.4rem;
  font-weight: 800;
  color: #92400E;
}

.quiz-actions-row {
  display: flex;
  justify-content: center;
  gap: 12px;
  flex-wrap: wrap;
}

.primary-big-btn {
  background: linear-gradient(135deg, #10B981 0%, #059669 100%);
  color: #FFFFFF;
  border: none;
  font-family: inherit;
  font-size: 1.15rem;
  font-weight: 800;
  padding: 12px 28px;
  border-radius: var(--radius-pill);
  cursor: pointer;
  box-shadow: 0 5px 0px #047857;
  transition: all 0.15s ease;
}

.primary-big-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 7px 0px #047857;
}

.secondary-big-btn {
  background: #F1F5F9;
  color: var(--text-dark);
  border: 3px solid #CBD5E1;
  font-family: inherit;
  font-size: 1.05rem;
  font-weight: 800;
  padding: 10px 22px;
  border-radius: var(--radius-pill);
  cursor: pointer;
  box-shadow: 0 4px 0px #94A3B8;
  transition: all 0.15s ease;
}

.secondary-big-btn:hover {
  background: #E2E8F0;
}

/* ================= SHAPE SORTER LAB STYLES ================= */
.sorter-container {
  max-width: 1040px;
  margin: 0 auto;
  width: 100%;
}

.sorter-card {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 30px 24px;
  box-shadow: var(--shadow-lg);
  border: 3px solid #E0E7FF;
}

.sorter-header-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
  flex-wrap: wrap;
  gap: 12px;
}

.sorter-header-left {
  display: flex;
  align-items: center;
  gap: 12px;
}

.sorter-back-btn {
  background: #F1F5F9;
  border: 2px solid #CBD5E1;
  padding: 6px 14px;
  border-radius: var(--radius-pill);
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 800;
  color: var(--text-dark);
  cursor: pointer;
  transition: all 0.15s ease;
}

.sorter-back-btn:hover {
  background: #E2E8F0;
  transform: translateX(-2px);
}

.sorter-header-right {
  display: flex;
  align-items: center;
  gap: 14px;
}

.sorter-counter {
  font-size: 0.95rem;
  font-weight: 800;
  color: var(--primary);
  background: #EEF2FF;
  padding: 4px 12px;
  border-radius: var(--radius-pill);
}

.sorter-instruction-banner {
  background: #EFF6FF;
  border-left: 4px solid #3B82F6;
  padding: 10px 16px;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 700;
  color: #1E3A8A;
  margin-bottom: 20px;
}

/* Sorter Bins Grid */
.sorter-bins-container {
  display: grid;
  gap: 16px;
  margin-bottom: 24px;
}

.sorter-bins-container.bins-2 {
  grid-template-columns: repeat(2, 1fr);
}

.sorter-bins-container.bins-3 {
  grid-template-columns: repeat(3, 1fr);
}

.sorter-bins-container.bins-4 {
  grid-template-columns: repeat(2, 1fr);
}

.sorter-bins-container.bins-5 {
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
}

@media (max-width: 768px) {
  .sorter-bins-container.bins-2,
  .sorter-bins-container.bins-3,
  .sorter-bins-container.bins-4,
  .sorter-bins-container.bins-5 {
    grid-template-columns: 1fr;
  }
}

.sorter-bin {
  background: #F8FAFC;
  border: 2px dashed #94A3B8;
  border-radius: var(--radius-md);
  padding: 12px;
  min-height: 170px;
  display: flex;
  flex-direction: column;
  transition: all 0.2s ease;
  cursor: pointer;
  position: relative;
}

.sorter-bin:hover {
  border-color: var(--bin-accent, var(--primary));
  background: #FFFFFF;
}

.sorter-bin.drag-over {
  border-color: var(--bin-accent, var(--primary));
  background: #EEF2FF;
  transform: scale(1.02);
  box-shadow: 0 8px 24px rgba(79, 70, 229, 0.18);
}

.sorter-bin.shake {
  animation: binShake 0.45s ease;
}

@keyframes binShake {
  0%, 100% { transform: translateX(0); }
  20%, 60% { transform: translateX(-8px); }
  40%, 80% { transform: translateX(8px); }
}

.bin-header {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  margin-bottom: 10px;
}

.bin-icon {
  font-size: 1.6rem;
}

.bin-titles {
  flex: 1;
}

.bin-titles h4 {
  font-size: 1.05rem;
  font-weight: 800;
  color: var(--text-dark);
  margin: 0;
}

.bin-subtitle {
  font-size: 0.76rem;
  font-weight: 700;
  color: var(--text-muted);
}

.bin-count {
  font-size: 0.85rem;
  font-weight: 900;
  background: #FFFFFF;
  color: var(--text-dark);
  padding: 2px 8px;
  border-radius: var(--radius-pill);
  border: 1px solid #CBD5E1;
}

.bin-drop-zone {
  flex: 1;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-content: flex-start;
  min-height: 80px;
}

.drop-placeholder {
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.85rem;
  font-weight: 700;
  color: #94A3B8;
  border: 1px dashed #CBD5E1;
  border-radius: var(--radius-sm);
  padding: 18px 8px;
}

.sorted-chip {
  background: #FFFFFF;
  border: 2px solid #10B981;
  border-radius: var(--radius-md);
  padding: 8px 10px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-width: 64px;
  box-shadow: 0 2px 6px rgba(16, 185, 129, 0.18);
  animation: popIn 0.25s ease;
  user-select: none;
}

.sorted-chip .chip-emoji {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2.2rem;
  line-height: 1.1;
  margin-bottom: 2px;
}

.sorted-chip .chip-emoji svg {
  display: block;
}

.sorted-chip .chip-name-sub {
  font-size: 0.68rem;
  font-weight: 800;
  color: #065F46;
  text-align: center;
  white-space: nowrap;
  max-width: 85px;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* Sorter Items Pool */
.sorter-pool-wrapper {
  background: #F1F5F9;
  border: 2px solid #E2E8F0;
  border-radius: var(--radius-lg);
  padding: 18px;
}

.pool-header-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 14px;
}

.pool-title {
  font-size: 1.1rem;
  font-weight: 800;
  color: var(--text-dark);
  margin: 0;
}

.pool-tip-text {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--text-muted);
}

.sorter-pool {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  min-height: 120px;
  align-items: center;
  justify-content: center;
}

.pool-empty-msg {
  width: 100%;
  text-align: center;
  padding: 24px;
  font-size: 1.15rem;
  font-weight: 800;
  color: #059669;
}

/* Visual-First Object Token Card */
.sorter-item-card {
  background: #FFFFFF;
  border: 2px solid #CBD5E1;
  border-radius: var(--radius-lg);
  padding: 14px 10px 10px 10px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 108px;
  min-height: 124px;
  cursor: grab;
  user-select: none;
  touch-action: manipulation;
  transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
  box-shadow: 0 4px 12px rgba(15, 23, 42, 0.08);
  position: relative;
}

.sorter-item-card:hover {
  transform: translateY(-5px) scale(1.04);
  border-color: var(--primary);
  box-shadow: 0 10px 22px rgba(79, 70, 229, 0.22);
}

.sorter-item-card:hover .item-visual {
  transform: scale(1.12);
}

.sorter-item-card.dragging {
  opacity: 0.35;
  transform: scale(0.92);
}

.sorter-item-card.selected {
  border-color: #3B82F6;
  background: #EFF6FF;
  transform: translateY(-6px) scale(1.08);
  box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.4), 0 12px 24px rgba(59, 130, 246, 0.25);
}

.item-visual-frame {
  width: 74px;
  height: 74px;
  background: #F8FAFC;
  border-radius: var(--radius-md);
  border: 1px solid #E2E8F0;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 8px;
  pointer-events: none;
}

.item-visual {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 3.4rem;
  line-height: 1;
  filter: drop-shadow(0 4px 6px rgba(0, 0, 0, 0.12));
  transition: transform 0.2s ease;
  pointer-events: none;
}

.item-visual svg {
  display: block;
}

.feedback-mini-icon {
  display: inline-flex;
  vertical-align: middle;
  margin: 0 4px;
}

.feedback-mini-icon svg {
  display: inline-block;
  vertical-align: middle;
}

.item-name {
  font-size: 0.76rem;
  font-weight: 800;
  color: var(--text-dark);
  text-align: center;
  line-height: 1.2;
  white-space: nowrap;
  max-width: 95px;
  overflow: hidden;
  text-overflow: ellipsis;
  pointer-events: none;
}

/* Footer */
.main-footer {
  text-align: center;
  padding: 24px 20px;
  background: #FFFFFF;
  border-top: 2px solid #E2E8F0;
  color: var(--text-muted);
  font-size: 0.88rem;
  margin-top: 30px;
}

.main-footer strong {
  color: var(--primary);
}

.main-footer .copyright {
  font-size: 0.78rem;
  margin-top: 4px;
}

/* ================= MOBILE & TABLET RESPONSIVENESS ================= */
@media (max-width: 1024px) {
  .stage-container {
    grid-template-columns: 1fr;
    gap: 14px;
  }

  /* Wide Stage is redundant when layout is stacked single column */
  #btnTheaterMode {
    display: none !important;
  }
}

@media (max-width: 768px) {
  .main-header {
    position: sticky;
    top: 0;
    transform: none !important;
    opacity: 1 !important;
    padding: 8px 14px;
    gap: 8px;
    box-shadow: 0 3px 12px rgba(79, 70, 229, 0.12);
  }

  .main-header.collapsed {
    transform: none !important;
    opacity: 1 !important;
  }

  .main-header::after {
    display: none !important;
  }

  .brand-logo {
    font-size: 1.4rem;
    padding: 4px 8px;
  }

  .brand-text h1 {
    font-size: 1.1rem;
  }

  .studio-badge {
    font-size: 0.65rem;
    padding: 1px 7px;
  }

  .mode-tab {
    padding: 6px 12px;
    font-size: 0.82rem;
  }

  .btn-sound-toggle {
    padding: 6px 10px;
    font-size: 0.8rem;
  }

  .app-container {
    padding: 6px 10px;
    margin-top: 10px;
  }

  /* 3D Canvas Responsive Height on Mobile */
  .canvas-wrapper {
    height: 68vh;
    min-height: 480px;
    max-height: 640px;
    border-width: 2px;
  }

  /* Details Panel flows naturally without massive fixed height */
  .shape-details-panel {
    height: auto;
    min-height: unset;
    padding: 14px;
    gap: 10px;
  }

  .prop-cards-grid {
    grid-template-columns: 1fr 1fr 1fr;
    gap: 8px;
  }

  .prop-card {
    padding: 10px 6px;
  }

  .prop-icon {
    font-size: 1.3rem;
  }

  .prop-number {
    font-size: 1.25rem;
  }

  .prop-label {
    font-size: 0.72rem;
  }

  .prop-desc {
    font-size: 0.68rem;
  }

  /* Bottom Toolbar Compact Fit */
  .canvas-bottom-bar {
    padding: 6px 8px;
    gap: 5px;
  }

  .bar-btn {
    padding: 5px 9px;
    font-size: 0.75rem;
    gap: 4px;
  }
}

@media (max-width: 580px) {
  .canvas-wrapper {
    height: 65vh;
    min-height: 450px;
  }

  .canvas-top-bar {
    top: 8px;
    left: 8px;
    right: 8px;
  }

  .display-mode-switch .mode-switch-btn {
    padding: 4px 9px;
    font-size: 0.72rem;
  }

  .hud-btn {
    padding: 4px 8px;
    font-size: 0.8rem;
  }

  /* Explode Slider & Palette Compact Mobile Stacking */
  .canvas-slider-card {
    top: 46px;
    left: 8px;
    min-width: 135px;
    padding: 4px 7px;
    gap: 3px;
  }

  .slider-title-row {
    font-size: 0.68rem;
  }

  .canvas-right-stack {
    top: 46px;
    right: 8px;
    gap: 4px;
  }

  .palette-toggle-btn {
    padding: 3px 8px;
    font-size: 0.72rem;
    gap: 4px;
  }

  .canvas-palette-card {
    padding: 4px 7px;
    gap: 5px;
  }

  .palette-label {
    font-size: 0.66rem;
  }

  .color-dot, .bg-swatch {
    width: 15px;
    height: 15px;
  }

  .prop-cards-grid {
    grid-template-columns: 1fr;
    gap: 8px;
  }

  .prop-card {
    display: flex;
    flex-direction: row;
    align-items: center;
    text-align: left;
    gap: 12px;
    padding: 10px 14px;
  }

  .bar-btn {
    padding: 5px 8px;
    font-size: 0.72rem;
  }

  .quiz-level-indicator {
    font-size: 1rem;
  }

  .quiz-question-body h3 {
    font-size: 1.15rem;
  }

  .question-illustration {
    font-size: 2.8rem;
  }

  .btn-next-question {
    padding: 10px 24px;
    font-size: 1rem;
  }

  /* Sorter Lab Mobile */
  .sorter-card {
    padding: 18px 12px;
  }

  .sorter-bins-container {
    gap: 12px;
  }

  .sorter-bin {
    min-height: 130px;
    padding: 10px;
  }

  .bin-icon {
    font-size: 1.3rem;
  }

  .bin-titles h4 {
    font-size: 0.92rem;
  }

  .sorter-pool {
    gap: 10px;
  }

  .sorter-item-card {
    width: 86px;
    min-height: 104px;
    padding: 10px 6px 8px 6px;
  }

  .item-visual-frame {
    width: 58px;
    height: 58px;
    margin-bottom: 6px;
  }

  .item-visual {
    font-size: 2.6rem;
  }

  .item-name {
    font-size: 0.68rem;
    max-width: 76px;
  }
}