/**
 * Academy - Component Stylesheet (Developer-Platform AI Laboratory Aesthetic)
 * Reusable components for app shell, curriculum tracks, lessons, quizzes,
 * interactive lab sandboxes, and mathematical layers.
 * Built with CSS Logical Properties (margin-inline, padding-inline, inset-inline).
 */

/* ==========================================================================
   1. App Layout & Shell
   ========================================================================== */
.app-container {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  position: relative;
}

.main-content {
  flex: 1;
  width: 100%;
  max-width: var(--container-max-width);
  margin-inline: auto;
  padding-inline: var(--space-4);
  padding-block: var(--space-8);
  position: relative;
  z-index: 1;
}

@media (min-width: 768px) {
  .main-content {
    padding-inline: var(--space-8);
    padding-block: var(--space-12);
  }
}

/* ==========================================================================
   2. Site Header & Modern Dev Navigation
   ========================================================================== */
.site-header {
  background-color: var(--color-bg-glass);
  border-bottom: 1px solid var(--color-border-glass);
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  box-shadow: 0 4px 20px -2px rgba(0, 0, 0, 0.4);
}

.header-inner {
  max-width: var(--container-max-width);
  margin-inline: auto;
  padding-inline: var(--space-4);
  padding-block: var(--space-3);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  flex-wrap: wrap;
}

@media (min-width: 768px) {
  .header-inner {
    padding-inline: var(--space-8);
    flex-wrap: nowrap;
  }
}

/* Brand Emblem */
.brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  text-decoration: none;
  color: var(--color-text-primary);
  font-weight: 700;
  font-size: 1.2rem;
  letter-spacing: -0.02em;
  transition: opacity var(--transition-fast);
}

.brand:hover {
  opacity: 0.9;
  text-decoration: none;
}

.brand__emblem {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  background: var(--color-bg-surface-elevated);
  border: 1px solid var(--color-border-glass);
  color: var(--color-accent-ai);
  box-shadow: 0 0 16px -2px var(--color-accent-ai-glow);
  flex-shrink: 0;
}

.brand__info {
  display: flex;
  flex-direction: column;
}

.brand__title {
  line-height: 1.1;
  font-weight: 800;
  letter-spacing: -0.02em;
}

.brand__status {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  text-transform: uppercase;
  color: var(--color-accent-ai);
  letter-spacing: 0.05em;
  display: flex;
  align-items: center;
  gap: 0.35rem;
}

.brand__status-dot {
  width: 6px;
  height: 6px;
  border-radius: var(--radius-full);
  background-color: var(--color-accent-ai);
  box-shadow: 0 0 8px var(--color-accent-ai);
}

/* Navigation Links */
.main-nav {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  overflow-x: auto;
  padding-block: var(--space-1);
  -webkit-overflow-scrolling: touch;
}

.nav-link {
  color: var(--color-text-secondary);
  font-weight: 500;
  font-size: 0.9rem;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  white-space: nowrap;
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  border: 1px solid transparent;
}

.nav-link:hover {
  color: var(--color-text-primary);
  background-color: var(--color-bg-surface-hover);
  border-color: var(--color-border-glass);
  text-decoration: none;
}

.nav-link.is-active {
  color: var(--color-accent-ai);
  background-color: var(--color-accent-ai-surface);
  border-color: rgba(56, 189, 248, 0.25);
  box-shadow: inset 0 0 12px var(--color-accent-ai-surface);
}

/* Header Controls (Theme, Language) */
.header-controls {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.ctrl-btn {
  background-color: var(--color-bg-surface-elevated);
  color: var(--color-text-secondary);
  border: 1px solid var(--color-border-glass);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  font-size: 0.8125rem;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  transition: all var(--transition-fast);
  box-shadow: inset 0 1px 0 0 var(--color-glass-highlight);
}

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

.ctrl-btn .icon-svg {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}

/* ==========================================================================
   3. Buttons & Interactive Controls
   ========================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  font-size: 0.9375rem;
  font-weight: 600;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  text-decoration: none;
  transition: all var(--transition-fast);
  text-align: center;
  line-height: 1.3;
  letter-spacing: -0.01em;
}

.btn:hover {
  text-decoration: none;
}

.btn--primary {
  background: var(--gradient-accent-ai);
  color: #ffffff;
  box-shadow: var(--shadow-glow-ai), inset 0 1px 0 rgba(255, 255, 255, 0.2);
}

.btn--primary:hover {
  box-shadow: 0 0 32px var(--color-accent-ai-glow), inset 0 1px 0 rgba(255, 255, 255, 0.3);
  transform: translateY(-1px);
  color: #ffffff;
}

.btn--secondary {
  background-color: var(--color-bg-surface-elevated);
  color: var(--color-text-primary);
  border: 1px solid var(--color-border-glass);
  box-shadow: var(--shadow-glass);
}

.btn--secondary:hover {
  background-color: var(--color-bg-surface-hover);
  border-color: var(--color-border-glass-hover);
  transform: translateY(-1px);
}

.btn--text {
  background: transparent;
  color: var(--color-accent-ai);
  padding-inline: 0;
  font-weight: 600;
}

.btn--text:hover {
  color: var(--color-accent-ai-hover);
}

/* ==========================================================================
   4. Badges, Tags & Telemetry Indicators
   ========================================================================== */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.2rem 0.5rem;
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  line-height: 1.2;
  letter-spacing: 0.02em;
}

.badge--pill {
  border-radius: var(--radius-full);
  padding-inline: var(--space-3);
  padding-block: var(--space-1);
}

.badge--coming-soon {
  background-color: var(--color-warning-bg);
  color: var(--color-warning-text);
  border: 1px solid var(--color-warning-border);
}

.badge__pulse {
  width: 6px;
  height: 6px;
  border-radius: var(--radius-full);
  background-color: currentColor;
  display: inline-block;
  opacity: 0.85;
}

.badge--ai {
  background-color: var(--color-accent-ai-surface);
  color: var(--color-accent-ai);
  border: 1px solid rgba(56, 189, 248, 0.3);
}

.badge--security {
  background-color: var(--color-accent-sec-surface);
  color: var(--color-accent-sec);
  border: 1px solid rgba(16, 185, 129, 0.3);
}

/* ==========================================================================
   5. Hero Section (AI Laboratory Cockpit)
   ========================================================================== */
.hero {
  text-align: center;
  padding-block: var(--space-8) var(--space-16);
  max-width: var(--content-max-width);
  margin-inline: auto;
  position: relative;
}

.hero__badge-wrapper {
  display: inline-flex;
  margin-block-end: var(--space-5);
}

.hero__badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-1) var(--space-4);
  background: var(--color-bg-surface-elevated);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-full);
  font-size: 0.8125rem;
  color: var(--color-accent-ai);
  font-weight: 600;
  box-shadow: 0 0 20px -4px var(--color-accent-ai-glow), inset 0 1px 0 var(--color-glass-highlight);
}

.hero__title {
  font-size: clamp(2.5rem, 6vw, 4.25rem);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.035em;
  margin-block-end: var(--space-5);
  background: linear-gradient(180deg, var(--color-text-glow) 30%, var(--color-text-secondary) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero__subtitle {
  font-size: clamp(1.05rem, 2vw, 1.25rem);
  color: var(--color-text-secondary);
  line-height: 1.65;
  margin-block-end: var(--space-8);
  max-width: 680px;
  margin-inline: auto;
}

.hero__actions {
  display: flex;
  justify-content: center;
  gap: var(--space-4);
  flex-wrap: wrap;
}

/* ==========================================================================
   6. Curriculum Tracks Grid (Laboratory Workbenches)
   ========================================================================== */
.tracks-section {
  margin-block-end: var(--space-16);
}

.section-header {
  margin-block-end: var(--space-8);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.section-header h2 {
  font-size: clamp(1.75rem, 3vw, 2.25rem);
  font-weight: 800;
  letter-spacing: -0.025em;
}

.section-desc {
  color: var(--color-text-secondary);
  font-size: 1.05rem;
  max-width: 680px;
}

.tracks-container {
  width: 100%;
}

.tracks-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-8);
}

@media (min-width: 840px) {
  .tracks-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.track-card {
  background: var(--color-bg-glass-card);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-xl);
  padding: var(--space-8);
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
  box-shadow: var(--shadow-glass);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: transform var(--transition-normal), border-color var(--transition-normal), box-shadow var(--transition-normal);
}

.track-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: transparent;
  transition: background var(--transition-normal);
}

.track-card--ai::before {
  background: var(--gradient-accent-ai);
}

.track-card--security::before {
  background: var(--gradient-accent-sec);
}

.track-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg), 0 0 32px -8px var(--color-accent-ai-glow);
}

.track-card--ai:hover {
  border-color: var(--color-border-glow-ai, rgba(56, 189, 248, 0.4));
  box-shadow: var(--shadow-lg), 0 0 32px -8px var(--color-accent-ai-glow);
}

.track-card--security:hover {
  border-color: var(--color-border-glow-sec, rgba(16, 185, 129, 0.4));
  box-shadow: var(--shadow-lg), 0 0 32px -8px var(--color-accent-sec-glow);
}

.track-card__header {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  margin-block-end: var(--space-5);
}

.track-card__icon-wrapper {
  width: 52px;
  height: 52px;
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  background-color: var(--color-bg-surface-elevated);
  border: 1px solid var(--color-border-glass);
}

.track-card--ai .track-card__icon-wrapper {
  color: var(--color-accent-ai);
  box-shadow: inset 0 0 16px var(--color-accent-ai-surface);
}

.track-card--security .track-card__icon-wrapper {
  color: var(--color-accent-sec);
  box-shadow: inset 0 0 16px var(--color-accent-sec-surface);
}

.track-card__meta {
  display: flex;
  flex-direction: column;
}

.track-card__num {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
  font-weight: 600;
}

.track-card__title {
  font-size: 1.4rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.track-card__title a {
  color: var(--color-text-primary);
}

.track-card__title a:hover {
  color: var(--color-accent-ai);
}

.track-card__desc {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  line-height: 1.6;
  margin-block-end: var(--space-4);
  flex-grow: 1;
}

.track-card__stats {
  margin-block-end: var(--space-4);
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex-wrap: wrap;
}

/* Track Card Levels Taxonomy */
.track-card__levels {
  background-color: var(--color-bg-canvas);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-4) var(--space-5);
  margin-block-end: var(--space-6);
}

.levels-title {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-block-end: var(--space-3);
  letter-spacing: 0.06em;
  font-weight: 600;
}

.level-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.level-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.9rem;
  padding-block: var(--space-1);
}

.level-item__name {
  font-weight: 500;
  color: var(--color-text-primary);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.level-index {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--color-text-muted);
  font-weight: 500;
}

.level-item__count {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

.track-card__footer {
  display: flex;
  gap: var(--space-3);
  align-items: center;
  flex-wrap: wrap;
  padding-block-start: var(--space-4);
  border-top: 1px solid var(--color-border-glass);
}

/* ==========================================================================
   7. Pillars Grid (Platform Principles)
   ========================================================================== */
.pillars-section {
  padding-block-start: var(--space-10);
  border-top: 1px solid var(--color-border-glass);
}

.pillars-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-6);
}

@media (min-width: 768px) {
  .pillars-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.pillar-card {
  background: var(--color-bg-glass-card);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  text-align: start;
  box-shadow: var(--shadow-glass);
  transition: transform var(--transition-fast), border-color var(--transition-fast);
}

.pillar-card:hover {
  transform: translateY(-2px);
  border-color: var(--color-border-glass-hover);
}

.pillar-card__icon {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  background-color: var(--color-bg-surface-elevated);
  border: 1px solid var(--color-border-glass);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-accent-ai);
  margin-block-end: var(--space-4);
}

.pillar-card h3 {
  font-size: 1.15rem;
  font-weight: 700;
  margin-block-end: var(--space-2);
  letter-spacing: -0.01em;
}

.pillar-card p {
  font-size: 0.925rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* ==========================================================================
   8. Panels, Safety Notices & Callouts
   ========================================================================== */
.panel {
  padding: var(--space-6);
  border-radius: var(--radius-lg);
  margin-block: var(--space-6);
  border-inline-start: 4px solid;
  background: var(--color-bg-glass-card);
  border-top: 1px solid var(--color-border-glass);
  border-right: 1px solid var(--color-border-glass);
  border-bottom: 1px solid var(--color-border-glass);
  box-shadow: var(--shadow-glass);
}

.panel--info {
  border-inline-start-color: var(--color-accent-ai);
}

.panel--warning {
  border-inline-start-color: var(--color-warning-border);
}

.safety-notice {
  background-color: var(--color-bg-surface-elevated);
  border: 1px solid var(--color-warning-border);
  border-inline-start: 4px solid var(--color-warning-border);
  border-radius: var(--radius-lg);
  padding: var(--space-5) var(--space-6);
  margin-block: var(--space-6);
  display: flex;
  gap: var(--space-4);
  align-items: flex-start;
  box-shadow: var(--shadow-glass);
}

.safety-notice--security {
  border-color: rgba(16, 185, 129, 0.4);
  border-inline-start-color: var(--color-accent-sec);
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.08) 0%, rgba(6, 182, 212, 0.04) 100%);
}

.safety-notice__icon {
  width: 28px;
  height: 28px;
  flex-shrink: 0;
  color: var(--color-accent-sec);
  margin-block-start: 2px;
}

.safety-notice__content {
  font-size: 0.95rem;
  line-height: 1.65;
}

/* ==========================================================================
   9. Reusable UI Components: Depth Layers, Quizzes, Lab Console
   ========================================================================== */

/* Math Callout & Display Components (KaTeX Integration) */
.math-display {
  display: block;
  overflow-x: auto;
  padding: var(--space-4) var(--space-6);
  margin-block: var(--space-6);
  direction: ltr !important;
  text-align: center;
  background: var(--color-bg-canvas);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}

.math-inline {
  display: inline-block;
  direction: ltr !important;
  unicode-bidi: isolate;
  margin-inline: 0.2rem;
  vertical-align: middle;
}

.math-error {
  display: inline-block;
  direction: ltr !important;
  unicode-bidi: isolate;
  color: #ef4444;
  background-color: rgba(239, 68, 68, 0.1);
  border: 1px dashed rgba(239, 68, 68, 0.4);
  padding: 0.15rem 0.4rem;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.85em;
}

/* Depth Layer Segmented Control (Reusable for Pass 2) */
.layer-switch {
  display: inline-flex;
  background-color: var(--color-bg-canvas);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-full);
  padding: 3px;
  gap: 2px;
}

.layer-pill {
  background: transparent;
  border: none;
  color: var(--color-text-secondary);
  padding: var(--space-1) var(--space-4);
  border-radius: var(--radius-full);
  font-size: 0.8125rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.layer-pill:hover {
  color: var(--color-text-primary);
}

.layer-pill.is-active {
  background: var(--color-bg-surface-elevated);
  color: var(--color-accent-ai);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
}

/* Lab Console / Sandbox Frame (Reusable for Pass 2 text & visual labs) */
.lab-container {
  background: var(--color-bg-base);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-xl);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
  margin-block: var(--space-6);
}

.lab-header {
  background-color: var(--color-bg-surface);
  border-bottom: 1px solid var(--color-border-glass);
  padding: var(--space-3) var(--space-4);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.lab-window-controls {
  display: flex;
  gap: 6px;
}

.lab-window-dot {
  width: 10px;
  height: 10px;
  border-radius: var(--radius-full);
  background-color: var(--color-border);
}

.lab-title {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  font-weight: 500;
}

.lab-status {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--color-accent-sec);
  display: flex;
  align-items: center;
  gap: 6px;
}

.lab-status::before {
  content: "";
  width: 6px;
  height: 6px;
  border-radius: var(--radius-full);
  background-color: var(--color-accent-sec);
  box-shadow: 0 0 6px var(--color-accent-sec);
}

.lab-terminal {
  padding: var(--space-4);
  background-color: #04060c;
  font-family: var(--font-mono);
  color: #38bdf8;
  font-size: 0.875rem;
  min-height: 180px;
}

/* Quiz Block Component (Pass 2 Quiz Engine) */
.quiz-block {
  background: var(--color-bg-glass-card);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  margin-block: var(--space-8);
  box-shadow: var(--shadow-glass);
}

.quiz-block__header {
  margin-block-end: var(--space-4);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.quiz-fieldset {
  border: none;
  padding: 0;
  margin: 0;
}

.quiz-form-wrapper {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.quiz-question {
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.015em;
  color: var(--color-text-primary);
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  margin-block: var(--space-4);
}

.quiz-options--binary {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-4);
  width: 100%;
}

.quiz-options--binary .quiz-option {
  justify-content: center;
  text-align: center;
  min-height: 48px;
}

@media (max-width: 520px) {
  .quiz-options--binary {
    grid-template-columns: 1fr;
  }
}

.quiz-option {
  background-color: var(--color-bg-surface-elevated);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-md);
  padding: var(--space-3) var(--space-4);
  font-size: 0.95rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  transition: all var(--transition-fast);
  color: var(--color-text-primary);
  user-select: none;
}

.quiz-option-text {
  font-size: var(--font-size-base);
  font-weight: 500;
  color: var(--color-text-primary);
  line-height: var(--line-height-normal);
  overflow-wrap: break-word;
}

.quiz-option:hover {
  background-color: var(--color-bg-surface-hover);
  border-color: var(--color-border-focus);
}

.quiz-option:focus-within {
  outline: 2px solid var(--color-border-focus);
}

.quiz-radio {
  accent-color: var(--color-accent-ai);
  width: 18px;
  height: 18px;
  cursor: pointer;
}

.quiz-fill-wrapper {
  display: flex;
  gap: var(--space-3);
  margin-block: var(--space-4);
  flex-wrap: wrap;
}

.quiz-input {
  flex: 1;
  min-width: 220px;
  background-color: var(--color-bg-glass-input);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-md);
  padding: var(--space-3) var(--space-4);
  color: var(--color-text-primary);
  font-size: 1rem;
}

.quiz-ordering-container {
  width: 100%;
}

.quiz-ordering-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  margin-block: var(--space-4);
}

.quiz-ordering-item {
  background-color: var(--color-bg-surface-elevated);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-md);
  padding: var(--space-3) var(--space-4);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
}

.quiz-ordering-handle {
  color: var(--color-text-muted);
  cursor: grab;
}

.quiz-ordering-text {
  flex: 1;
}

.quiz-ordering-buttons {
  display: flex;
  gap: var(--space-2);
}

.btn-order-move {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 44px;
  min-height: 44px;
  background-color: var(--color-bg-surface);
  border: 1px solid var(--color-border);
  color: var(--color-text-secondary);
  border-radius: var(--radius-md);
  padding: var(--space-2);
  font-size: var(--font-size-sm);
  font-weight: 600;
  cursor: pointer;
  transition: background-color var(--transition-fast), border-color var(--transition-fast), color var(--transition-fast);
}

.btn-order-up,
.btn-order-down {
  /* Inherits .btn-order-move touch target */
}

.btn-order-move:hover:not(:disabled) {
  background-color: var(--color-bg-surface-hover);
  color: var(--color-text-primary);
  border-color: var(--color-border-focus);
}

.btn-order-move:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

.btn-order-move:disabled {
  opacity: 0.35;
  cursor: not-allowed;
  pointer-events: none;
  border-color: var(--color-border-subtle);
}

.quiz-actions {
  margin-block-start: var(--space-4);
}

.btn--submit-quiz {
  min-height: 44px;
  padding: var(--space-2) var(--space-6);
  font-weight: 600;
  font-size: var(--font-size-base);
}

.quiz-feedback-region {
  width: 100%;
  min-height: 0;
}

.quiz-feedback-box {
  padding: var(--space-4) var(--space-5);
  border-radius: var(--radius-md);
  margin-block-start: var(--space-4);
  border-inline-start: 4px solid;
}

.quiz-feedback--correct {
  background-color: var(--color-accent-sec-surface);
  border-color: var(--color-accent-sec);
  color: var(--color-accent-sec);
}

.quiz-feedback--incorrect {
  background-color: var(--color-danger-bg);
  border-color: var(--color-danger-border);
  color: var(--color-danger-text);
}

.quiz-feedback-header {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 1.05rem;
  margin-block-end: var(--space-1);
}

.quiz-feedback-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  font-weight: 700;
  line-height: 1;
  flex-shrink: 0;
}

.quiz-feedback-explanation {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  margin-block-start: var(--space-2);
}

.quiz-retry-wrapper {
  margin-block-start: var(--space-3);
}

.btn--retry-quiz {
  min-height: 44px;
  padding: var(--space-2) var(--space-5);
  font-weight: 600;
  font-size: var(--font-size-sm);
}

/* ==========================================================================
   10. Placeholder Views & Track Details
   ========================================================================== */
.placeholder-view, .track-detail, .about-view, .not-found-view {
  max-width: var(--content-max-width);
  margin-inline: auto;
}

.breadcrumb {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-block-end: var(--space-6);
  flex-wrap: wrap;
}

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

.breadcrumb [aria-current="page"] {
  color: var(--color-text-primary);
  font-weight: 500;
}

.track-header, .placeholder-header, .about-header {
  margin-block-end: var(--space-8);
}

.track-header h1, .placeholder-header h1, .about-header h1 {
  font-size: clamp(2rem, 4vw, 2.75rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-block: var(--space-3);
}

.track-header__desc, .placeholder-desc, .about-lead {
  font-size: 1.15rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* Track Detail Levels Grid */
.levels-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
  margin-block: var(--space-6);
}

.level-card {
  background: var(--color-bg-glass-card);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  box-shadow: var(--shadow-glass);
}

.level-card__header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-block-end: var(--space-3);
}

.level-card__index {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--color-accent-ai);
  letter-spacing: 0.08em;
}

.level-card__title {
  font-size: 1.3rem;
  font-weight: 700;
  margin-block-end: var(--space-2);
  letter-spacing: -0.015em;
}

.level-card__desc {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  margin-block-end: var(--space-4);
  line-height: 1.6;
}

.level-card__meta {
  display: flex;
  gap: var(--space-4);
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  font-family: var(--font-mono);
}

.level-progress-line {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-block-end: var(--space-4);
  font-weight: 500;
}

.level-lesson-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.level-lesson-item {
  list-style: none;
}

.level-lesson-link {
  display: block;
  text-decoration: none;
  padding: var(--space-4);
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  transition: border-color var(--transition-fast), background-color var(--transition-fast), transform var(--transition-fast);
}

.level-lesson-link:hover {
  border-color: var(--color-accent-ai);
  background: var(--color-bg-card-hover, var(--color-bg-card));
  transform: translateY(-1px);
}

.level-lesson-link:focus-visible {
  outline: 2px solid var(--color-accent-ai);
  outline-offset: 2px;
}

.badge--status-not-started {
  background-color: var(--color-bg-subtle, rgba(255, 255, 255, 0.05));
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
}

.badge--success {
  background-color: var(--color-accent-sec-surface);
  color: var(--color-accent-sec);
  border: 1px solid rgba(16, 185, 129, 0.3);
}

.badge--warning {
  background-color: var(--color-warning-bg);
  color: var(--color-warning-text);
  border: 1px solid var(--color-warning-border);
}

.track-header {
  display: flex;
  align-items: flex-start;
  gap: var(--space-4);
  flex-wrap: wrap;
}

.track-header .track-card__icon-wrapper {
  margin-block-end: var(--space-4);
}

.track-header__info {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  flex: 1 1 0;
  min-width: 0;
}

.track-levels {
  margin-block-start: var(--space-8);
  width: 100%;
}

.track-levels > h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text-primary);
  margin-block-end: var(--space-6);
}

.levels-container {
  width: 100%;
}

.level-lesson-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  flex-wrap: wrap;
  width: 100%;
}

.level-lesson-title-group {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  min-width: 0;
  flex: 1 1 auto;
}

.level-lesson-num {
  font-family: var(--font-mono);
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  font-weight: 600;
  flex-shrink: 0;
}

.level-lesson-title {
  font-size: var(--font-size-base);
  font-weight: 600;
  color: var(--color-text-primary);
  margin: 0;
  overflow-wrap: break-word;
  word-break: break-word;
}

.level-lesson-summary {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height-prose);
  margin-block-start: var(--space-2);
  margin-block-end: 0;
  overflow-wrap: break-word;
}

.level-lesson-meta {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  margin-block-start: var(--space-3);
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
}

.lesson-meta-time {
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
}

.track-footer {
  margin-block-start: var(--space-8);
  padding-block-start: var(--space-4);
}

.error-state-panel {
  padding: var(--space-6);
  text-align: center;
  margin-block: var(--space-4);
}

.error-state-title {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--color-text-primary);
  margin-block-end: var(--space-2);
}

.error-state-desc {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin-block-end: var(--space-4);
}

.btn-retry-load {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding-inline: var(--space-4);
}

.loading-state-panel {
  padding: var(--space-12);
  text-align: center;
  color: var(--color-text-muted);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--space-4);
}

.loading-state-panel .brand__status-dot {
  margin: 0 auto;
  width: 12px;
  height: 12px;
}

.loading-state-text {
  font-size: var(--font-size-base);
  font-weight: 500;
}

/* Search Box Mockup */
.search-box-mockup {
  margin-block: var(--space-6);
}

.search-input-wrapper {
  position: relative;
  display: flex;
  align-items: center;
}

.search-icon {
  position: absolute;
  inset-inline-start: var(--space-4);
  color: var(--color-text-muted);
  pointer-events: none;
  display: flex;
  align-items: center;
}

.search-input {
  width: 100%;
  padding: var(--space-4) var(--space-5);
  padding-inline-start: var(--space-12);
  background-color: var(--color-bg-glass-input);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-lg);
  color: var(--color-text-primary);
  font-size: 1rem;
  box-shadow: var(--shadow-glass);
}

.search-input:disabled {
  opacity: 0.75;
  cursor: not-allowed;
}

/* Progress Stats Mockup */
.progress-stats-preview {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--space-4);
  margin-block: var(--space-6);
}

.stat-card {
  background: var(--color-bg-glass-card);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  text-align: center;
  box-shadow: var(--shadow-glass);
}

.stat-card__value {
  font-family: var(--font-mono);
  font-size: 2.25rem;
  font-weight: 800;
  color: var(--color-accent-ai);
  margin-block-end: var(--space-1);
}

.stat-card__label {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
}

/* About Principles */
.about-section {
  margin-block-end: var(--space-10);
}

.about-section h2 {
  font-size: 1.5rem;
  font-weight: 700;
  margin-block-end: var(--space-3);
  letter-spacing: -0.02em;
}

.principles-list {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
  margin-block-start: var(--space-4);
}

.principle-item {
  background: var(--color-bg-glass-card);
  border: 1px solid var(--color-border-glass);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  box-shadow: var(--shadow-glass);
}

.principle-item h3 {
  font-size: 1.15rem;
  margin-block-end: var(--space-2);
}

.principle-item p {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  line-height: 1.6;
}

/* 404 Not Found */
.not-found-view {
  text-align: center;
  padding-block: var(--space-16);
}

.not-found-code {
  font-family: var(--font-mono);
  font-size: clamp(5rem, 16vw, 9rem);
  font-weight: 900;
  line-height: 1;
  background: linear-gradient(180deg, var(--color-border-focus) 0%, rgba(26, 39, 68, 0.4) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-block-end: var(--space-4);
}

.not-found-desc {
  font-size: 1.2rem;
  color: var(--color-text-secondary);
  margin-block-end: var(--space-4);
}

.not-found-path {
  margin-block-end: var(--space-6);
}

.not-found-actions, .placeholder-actions, .about-actions {
  margin-block-start: var(--space-8);
}

/* ==========================================================================
   11. Site Footer
   ========================================================================== */
.site-footer {
  background-color: var(--color-bg-surface);
  border-top: 1px solid var(--color-border-glass);
  padding-block: var(--space-10);
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

.footer-inner {
  max-width: var(--container-max-width);
  margin-inline: auto;
  padding-inline: var(--space-4);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-6);
}

@media (min-width: 768px) {
  .footer-inner {
    padding-inline: var(--space-8);
  }
}

.footer-info {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.footer-subtext {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

.footer-links {
  display: flex;
  gap: var(--space-5);
  list-style: none;
}

.footer-links a {
  color: var(--color-text-secondary);
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: var(--color-accent-ai);
}

/* ==========================================================================
   14. In-Page Modal Dialogs & Progress Components
   ========================================================================== */
.modal-dialog-backdrop {
  position: fixed;
  inset: 0;
  background-color: rgba(0, 0, 0, 0.75);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: var(--space-4);
}

.modal-dialog-backdrop[hidden] {
  display: none !important;
}

.modal-dialog-card {
  width: 100%;
  max-width: 480px;
  background: var(--color-bg-elevated);
  border: 1px solid var(--color-border);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.5);
  animation: modalFadeIn 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

@keyframes modalFadeIn {
  from {
    opacity: 0;
    transform: scale(0.96);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

.btn--success {
  background-color: rgba(34, 197, 94, 0.15);
  color: #4ade80;
  border: 1px solid rgba(34, 197, 94, 0.35);
}

.btn--success:hover {
  background-color: rgba(34, 197, 94, 0.25);
  border-color: rgba(34, 197, 94, 0.5);
}


/* ==========================================================================
   15. Lesson Reading Layout & Collapsible Table of Contents
   ========================================================================== */
.lesson-viewport-wrapper {
  width: 100%;
  min-height: 50vh;
}

.lesson-loading-text {
  font-size: var(--font-size-base);
  color: var(--color-text-muted);
  font-weight: 500;
  text-align: center;
}

.lesson-placeholder {
  max-width: var(--content-max-width);
  margin-inline: auto;
  padding: var(--space-6);
}

.lesson-view {
  max-width: var(--container-max-width);
  margin-inline: auto;
  padding-inline: var(--space-4);
  padding-block: var(--space-4) var(--space-12);
  width: 100%;
}

.lesson-duration {
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
}

.lesson-summary {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  line-height: var(--line-height-prose);
  margin-block: var(--space-3) var(--space-6);
  max-width: var(--prose-max-width);
}

.lesson-layer-control-panel {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  flex-wrap: wrap;
  margin-block: var(--space-4) var(--space-6);
  padding: var(--space-3) var(--space-4);
  background: var(--color-bg-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
}

.layer-control-label {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-text-primary);
}

.lesson-reading-progress {
  position: sticky;
  top: 56px;
  width: 100%;
  height: 3px;
  background-color: var(--color-border-subtle);
  z-index: 95;
}

.lesson-reading-progress-bar {
  height: 100%;
  width: 0%;
  background: var(--gradient-accent-ai);
  transition: width 120ms ease-out;
}

.lesson-layout,
.lesson-container-layout {
  display: flex;
  flex-direction: column;
  gap: var(--space-8);
  margin-block-start: var(--space-6);
  width: 100%;
}

.lesson-toc {
  width: 100%;
  min-width: 0;
}

/* Collapsible Table of Contents */
.toc-collapsible {
  background: var(--color-bg-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
  box-shadow: var(--shadow-sm);
  width: 100%;
}

.toc-collapsible-summary {
  font-weight: 600;
  font-size: var(--font-size-sm);
  color: var(--color-text-primary);
  cursor: pointer;
  padding: var(--space-2) var(--space-1);
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  user-select: none;
}

.toc-collapsible-summary::-webkit-details-marker {
  display: none;
}

.toc-collapsible-summary:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

.toc-collapsible[open] .toc-collapsible-summary {
  border-block-end: 1px solid var(--color-border-subtle);
  margin-block-end: var(--space-3);
  padding-block-end: var(--space-2);
}

.lesson-toc-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.toc-item {
  list-style: none;
  font-size: var(--font-size-sm);
  line-height: var(--line-height-normal);
}

.toc-item a {
  display: block;
  color: var(--color-text-secondary);
  text-decoration: none;
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm);
  transition: background-color var(--transition-fast, 150ms ease), color var(--transition-fast, 150ms ease);
  overflow-wrap: break-word;
  word-break: break-word;
}

.toc-item a:hover {
  color: var(--color-accent-ai);
  background-color: var(--color-accent-ai-surface);
}

.toc-item a:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

.toc-item.is-active a,
.toc-item a[aria-current="true"],
.toc-item a[aria-current="location"] {
  color: var(--color-accent-ai);
  font-weight: 600;
  background-color: var(--color-accent-ai-surface);
  border-inline-start: 2px solid var(--color-accent-ai);
}

.toc-item--h2 {
  padding-inline-start: 0;
  font-weight: 500;
}

.toc-item--h3 {
  padding-inline-start: var(--space-3);
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
}

.toc-empty {
  list-style: none;
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
  font-style: italic;
  padding: var(--space-2);
}

@media (min-width: 1024px) {
  .lesson-layout,
  .lesson-container-layout {
    display: grid;
    grid-template-columns: 280px minmax(0, 1fr);
    align-items: start;
    gap: var(--space-8);
  }

  .lesson-toc {
    position: sticky;
    top: calc(56px + var(--space-6));
    max-height: calc(100vh - 80px);
    overflow-y: auto;
  }
}

.lesson-prose-container {
  max-width: var(--prose-max-width);
  width: 100%;
  margin-inline: auto;
}

.lesson-blocks-container {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
  line-height: var(--line-height-prose);
}

.lesson-blocks-container p {
  max-width: var(--prose-max-width);
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
}

/* Heading Hierarchy */
.lesson-title {
  font-size: clamp(1.75rem, 4vw, 2.35rem);
  font-weight: 700;
  line-height: var(--line-height-tight);
  color: var(--color-text-primary);
  margin-block: var(--space-4) var(--space-2);
}

.lesson-blocks-container h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text-primary);
  margin-block-start: var(--space-8);
  margin-block-end: var(--space-3);
  padding-block-end: var(--space-2);
  border-block-end: 1px solid var(--color-border-subtle);
}

.lesson-blocks-container h3 {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--color-text-primary);
  margin-block-start: var(--space-6);
  margin-block-end: var(--space-2);
}

.lesson-blocks-container h4 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--color-text-muted);
  margin-block-start: var(--space-4);
  margin-block-end: var(--space-2);
}

/* ==========================================================================
   16. Lesson Navigation & Completion Button
   ========================================================================== */
.btn-toggle-lesson-complete {
  margin-inline-start: auto;
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  min-height: 44px;
  padding: var(--space-2) var(--space-3);
  font-size: var(--font-size-sm);
  font-weight: 600;
  border-radius: var(--radius-md);
  cursor: pointer;
  text-decoration: none;
  transition: background-color var(--transition-fast), border-color var(--transition-fast), color var(--transition-fast);
}

.btn-toggle-lesson-complete:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

.btn-complete-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1rem;
  line-height: 1;
}

.btn-complete-text {
  white-space: nowrap;
}

.lesson-nav-footer {
  display: flex;
  justify-content: space-between;
  align-items: stretch;
  gap: var(--space-4);
  margin-block-start: var(--space-10);
  padding-block-start: var(--space-6);
  border-block-start: 1px solid var(--color-border-subtle);
  width: 100%;
}

.lesson-nav-btn {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  min-height: 44px;
  padding: var(--space-3) var(--space-4);
  background-color: var(--color-bg-surface-elevated);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  color: var(--color-text-primary);
  text-decoration: none;
  max-width: 48%;
  flex: 1 1 0;
  transition: border-color var(--transition-fast), background-color var(--transition-fast);
}

.lesson-nav-btn:hover {
  background-color: var(--color-bg-surface-hover);
  border-color: var(--color-border-focus);
}

.lesson-nav-btn:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

.lesson-nav-btn--prev {
  align-items: flex-start;
  text-align: start;
}

.lesson-nav-btn--next {
  align-items: flex-end;
  text-align: end;
  margin-inline-start: auto;
}

.lesson-nav-dir {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
}

.lesson-nav-title {
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text-primary);
  line-height: var(--line-height-tight);
}

/* RTL Arrow Flipping */
html[dir="rtl"] .lesson-nav-btn [data-dir-icon],
html[dir="rtl"] .lesson-nav-btn .icon-svg {
  transform: scaleX(-1);
}

@media (max-width: 640px) {
  .lesson-nav-footer {
    flex-direction: column;
    gap: var(--space-3);
  }

  .lesson-nav-btn {
    max-width: 100%;
    width: 100%;
    align-items: flex-start;
    text-align: start;
  }

  .lesson-nav-btn--next {
    align-items: flex-start;
    text-align: start;
    margin-inline-start: 0;
  }
}

/* ==========================================================================
   17. Non-Interactive Lab & Visual Placeholders
   ========================================================================== */
.simulation-placeholder, .lab-placeholder-unregistered, .visual-placeholder {
  background: var(--color-bg-surface);
  border: 1px dashed var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-8) var(--space-6);
  text-align: center;
  margin-block: var(--space-6);
}

.simulation-placeholder .badge--coming-soon,
.visual-placeholder .badge--coming-soon {
  display: inline-block;
  margin-block-end: var(--space-3);
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  padding: var(--space-1) var(--space-3);
  background: rgba(255, 255, 255, 0.05);
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
}

.simulation-placeholder h4, .visual-placeholder h4 {
  font-size: 1.15rem;
  color: var(--color-text-primary);
  margin-block-end: var(--space-2);
}

.simulation-placeholder p, .visual-placeholder p {
  color: var(--color-text-muted);
  font-size: 0.9rem;
  max-width: 500px;
  margin-inline: auto;
}

/* ==========================================================================
   17. Responsive Mobile Shield (360px Viewport No Horizontal Overflow)
   ========================================================================== */
@media (max-width: 480px) {
  .main-content {
    padding-inline: var(--space-3);
  }

  .card, .panel, .lesson-header, .search-box-container {
    padding: var(--space-4);
    max-width: 100%;
    overflow-x: hidden;
  }

  .layer-switch {
    width: 100%;
    overflow-x: auto;
  }

  .lesson-meta-bar {
    flex-wrap: wrap;
    gap: var(--space-2);
  }
}

/* ==========================================================================
   PWA Offline Banner & Status Badge
   ========================================================================== */
.pwa-update-banner {
  position: fixed;
  bottom: var(--space-6);
  inset-inline-end: var(--space-6);
  z-index: 1000;
  max-width: 480px;
  background: var(--color-bg-surface-elevated);
  border: 1px solid var(--color-border-focus);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
  box-shadow: var(--shadow-lg), var(--shadow-glow-ai);
  animation: slideInUp 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

.status-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: 2px 8px;
  border-radius: var(--radius-full);
  background: var(--color-bg-surface);
  border: 1px solid var(--color-border);
  font-size: 0.75rem;
  color: var(--color-text-secondary);
}

.status-dot {
  width: 6px;
  height: 6px;
  border-radius: var(--radius-full);
}

.status-dot--ready,
.status-dot--online {
  background-color: var(--color-accent-sec);
  box-shadow: 0 0 6px var(--color-accent-sec);
}

.status-dot--warning {
  background-color: var(--color-warning-border);
  box-shadow: 0 0 6px var(--color-warning-border);
}

@keyframes slideInUp {
  from {
    opacity: 0;
    transform: translateY(16px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ==========================================================================
   18. Embedded Lab Sandboxes & Host Isolation
   ========================================================================== */
[data-embedded] header.top,
[data-embedded] .toolbar,
[data-embedded] .brand,
.academy-lab-wrapper[data-embedded] header.top,
.ml-temperature[data-embedded] header.top,
.ml-neural[data-embedded] header.top,
.ml-token[data-embedded] header.top {
  display: none !important;
}


/* Theme picker (header) */
.ctrl-select {
  background-color: var(--color-bg-surface-elevated);
  color: var(--color-text-secondary);
  border: 1px solid var(--color-border-glass);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  font-size: 0.8125rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  max-width: 11rem;
  min-height: 2.25rem;
}
.ctrl-select:hover {
  color: var(--color-text-primary);
  border-color: var(--color-border-glass-hover);
}

/* Mission card (lesson block) */
.mission-card {
  display: grid;
  gap: var(--space-3);
  padding: var(--space-5);
  margin-block: var(--space-6);
  border: 1px solid var(--color-border-glass-hover);
  border-inline-start: 4px solid var(--color-accent-brand);
  border-radius: var(--radius-lg);
  background: var(--color-bg-glass-card);
  box-shadow: var(--shadow-glass);
}
.mission-card__title { margin: 0; font-size: 1.15rem; }
.mission-card__desc, .mission-card__status { margin: 0; color: var(--color-text-secondary); }
.mission-card__play { justify-self: start; }

/* ===== 90-Day AI Journey ===== */
.journey-view { display: grid; gap: var(--space-6); min-width: 0; }
.journey-header { display: grid; gap: var(--space-2); }
.journey-header h1 { margin: 0; text-wrap: balance; }
.journey-header .journey-badge, .journey-header .badge { justify-self: start; }
.journey-panel-open { margin: 0; }
.journey-lead, .journey-muted { color: var(--color-text-secondary); margin: 0; }
.journey-eyebrow { margin: 0; color: var(--color-text-secondary); font-size: var(--font-size-sm); }
.journey-section { display: grid; gap: var(--space-3); }
.journey-section h2, .journey-progress h2, .journey-steps h2 { margin: 0; font-size: var(--font-size-xl); }
.journey-entry { display: grid; gap: var(--space-3); margin-block: var(--space-6); }
.journey-entry > * { margin: 0; }
.journey-progress { display: grid; gap: var(--space-4); }
.journey-bar { block-size: 0.6rem; border-radius: var(--radius-full); background: var(--color-bg-surface-elevated); border: 1px solid var(--color-border); overflow: hidden; }
.journey-bar > span { display: block; block-size: 100%; background: var(--gradient-brand); }
.journey-stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(10rem, 1fr)); gap: var(--space-3); margin: 0; }
.journey-stats > div { padding: var(--space-3); border: 1px solid var(--color-border); border-radius: var(--radius-md); background: var(--color-bg-surface); min-width: 0; }
.journey-stats dt { color: var(--color-text-secondary); font-size: var(--font-size-sm); }
.journey-stats dd { margin: 0; font-size: var(--font-size-lg); font-weight: 600; overflow-wrap: anywhere; }
.journey-actions { display: flex; flex-wrap: wrap; gap: var(--space-3); align-items: center; }
.journey-actions .btn { white-space: normal; text-align: center; }
.journey-note { margin: 0; color: var(--color-text-secondary); }
.journey-banner { padding: var(--space-3) var(--space-4); border-radius: var(--radius-md); border: 1px solid var(--color-success-border); background: var(--color-success-bg); color: var(--color-success-text); }
.journey-banner--planned { border-color: var(--color-info-border); background: var(--color-info-bg); color: var(--color-info-text); }
.journey-banner--blocked { border-color: var(--color-warning-border); background: var(--color-warning-bg); color: var(--color-warning-text); }
.journey-banner a { color: inherit; text-decoration: underline; }
.journey-phase-list, .journey-weeks, .journey-day-list, .journey-links { list-style: none; margin: 0; padding: 0; display: grid; gap: var(--space-3); }
.journey-phase-row { display: grid; gap: var(--space-2); padding: var(--space-4); border: 1px solid var(--color-border); border-radius: var(--radius-md); background: var(--color-bg-surface); }
.journey-phase-row__head { display: flex; flex-wrap: wrap; gap: var(--space-2); justify-content: space-between; align-items: center; }
.journey-weeks { grid-template-columns: repeat(auto-fill, minmax(9.5rem, 1fr)); }
.journey-week { display: grid; gap: 2px; padding: var(--space-3); border: 1px dashed var(--color-border); border-radius: var(--radius-md); min-width: 0; }
.journey-week.is-complete { border-style: solid; border-color: var(--color-success-border); background: var(--color-success-bg); }
.journey-week__n { font-weight: 600; }
.journey-week__flag { color: var(--color-success-text); font-size: var(--font-size-sm); min-block-size: 1.2em; }
.journey-group { border: 1px solid var(--color-border); border-radius: var(--radius-md); background: var(--color-bg-surface); padding: var(--space-3) var(--space-4); }
.journey-group > summary { cursor: pointer; font-weight: 600; padding-block: var(--space-2); }
.journey-group .journey-day-list { margin-block-start: var(--space-3); gap: var(--space-2); }
.journey-day-link { display: grid; grid-template-columns: 2.5rem minmax(0, 1fr) auto; gap: var(--space-1) var(--space-3); align-items: center; padding: var(--space-3); border: 1px solid var(--color-border-subtle); border-radius: var(--radius-md); color: var(--color-text-primary); text-decoration: none; }
.journey-day-link:hover { border-color: var(--color-border-glass-hover); background: var(--color-bg-surface-hover); }
.journey-day-link__n { font-weight: 700; color: var(--color-accent-brand); text-align: center; }
.journey-day-link__t { min-width: 0; overflow-wrap: anywhere; }
.journey-day-link .journey-badge { grid-column: 2 / -1; justify-self: start; }
.journey-day-link--planned, .journey-day-link--blocked { opacity: 0.8; }
.journey-badge { display: inline-block; padding: 2px var(--space-2); border-radius: var(--radius-full); font-size: var(--font-size-xs); border: 1px solid var(--color-border); color: var(--color-text-secondary); }
.journey-badge--done { border-color: var(--color-success-border); color: var(--color-success-text); background: var(--color-success-bg); }
.journey-badge--open { border-color: var(--color-info-border); color: var(--color-info-text); background: var(--color-info-bg); }
.journey-badge--blocked { border-color: var(--color-warning-border); color: var(--color-warning-text); background: var(--color-warning-bg); }
.journey-steps { list-style: none; margin: 0; padding: 0; display: grid; gap: var(--space-3); }
.journey-steps > li { padding: var(--space-4); border: 1px solid var(--color-border); border-radius: var(--radius-md); background: var(--color-bg-surface); display: grid; gap: var(--space-2); }
.journey-steps p { margin: 0; line-height: var(--line-height-prose); }
.journey-link { display: block; padding: var(--space-3); border: 1px solid var(--color-border); border-radius: var(--radius-md); color: var(--color-text-primary); text-decoration: none; overflow-wrap: anywhere; }
.journey-link:hover { border-color: var(--color-border-glass-hover); }
.journey-link__kind { color: var(--color-accent-brand); font-size: var(--font-size-sm); font-weight: 600; margin-inline-end: var(--space-2); }
.journey-daynav { display: flex; flex-wrap: wrap; gap: var(--space-3); justify-content: space-between; }
.journey-daynav .btn { white-space: normal; }
.journey-cert, .journey-reset { display: grid; gap: var(--space-3); }
.journey-cert > *, .journey-reset > * { margin: 0; }
.journey-input { inline-size: 100%; max-inline-size: 28rem; padding: var(--space-2) var(--space-3); border-radius: var(--radius-md); border: 1px solid var(--color-border); background: var(--color-bg-glass-input); color: var(--color-text-primary); font: inherit; }
.journey-cert-preview svg { inline-size: 100%; max-inline-size: 40rem; block-size: auto; border-radius: var(--radius-md); }
.journey-confirm { display: flex; flex-wrap: wrap; gap: var(--space-3); align-items: center; padding: var(--space-3); border: 1px solid var(--color-danger-border); border-radius: var(--radius-md); background: var(--color-danger-bg); }
.journey-confirm[hidden] { display: none; }
.journey-confirm p { flex-basis: 100%; }
.journey-view a:focus-visible, .journey-view button:focus-visible, .journey-view input:focus-visible, .journey-view summary:focus-visible, .journey-entry a:focus-visible {
  outline: 2px solid var(--color-focus-ring); outline-offset: 2px;
}
@media (max-width: 30rem) {
  .journey-day-link { grid-template-columns: 2rem minmax(0, 1fr); }
  .journey-day-link .journey-muted { display: none; }
  .journey-actions .btn, .journey-daynav .btn { inline-size: 100%; }
}
@media (prefers-reduced-motion: reduce) {
  .journey-view *, .journey-entry * { transition: none !important; animation: none !important; }
}