.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: 11px 16px;
  border-radius: var(--radius-sm);
  font-size: 0.92rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  border: 1px solid transparent;
  transition: background var(--transition), border-color var(--transition), color var(--transition), transform var(--transition), box-shadow var(--transition);
  white-space: nowrap;
}

.btn-primary {
  background: var(--accent);
  color: #fff;
  box-shadow: 0 12px 22px color-mix(in srgb, var(--accent) 18%, transparent);
}
.btn-primary:hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
}
.btn:active { transform: translateY(0) scale(0.98); }
.btn-primary:disabled { opacity: 0.5; cursor: not-allowed; }

.btn-secondary {
  background: var(--bg-card);
  color: var(--text-primary);
  border: 1px solid transparent;
}
.btn-secondary:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-light);
  transform: translateY(-1px);
}

.btn-danger {
  background: #dc3545;
  color: #fff;
  border: 1px solid #dc3545;
}
.btn-danger:hover { background: #bb2d3b; border-color: #bb2d3b; }

.btn-sm { padding: 4px 12px; font-size: 0.85rem; }

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
}
.btn-ghost:hover {
  color: var(--text-primary);
  background: color-mix(in srgb, var(--accent) 8%, var(--bg-card));
}

.btn-success { background: var(--success); color: #0f1117; }
.btn-error { background: var(--error); color: #0f1117; }

.btn-lg {
  padding: var(--spacing-md) var(--spacing-xl);
  font-size: 1.05rem;
}

.btn-sm {
  padding: var(--spacing-xs) var(--spacing-md);
  font-size: 0.85rem;
}

.btn-block { width: 100%; }

/* Cards */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--spacing-lg);
  box-shadow: var(--shadow-soft);
}

.card-hover:hover {
  border-color: var(--border-light);
  background: var(--bg-card-hover);
  transform: translateY(-2px);
}

/* Quiz chooser card variants (legacy — kept for tier chooser) */
.quiz-card {
  position: relative;
  transition: border-color 0.2s, transform 0.15s, box-shadow 0.2s;
}
.quiz-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
}
.quiz-card--lecture  { border-left-color: var(--card-lecture); }
.quiz-card--expert   { border-left-color: var(--card-expert); }
.quiz-card--recall   { border-left-color: var(--card-recall); }
.quiz-card--official { border-left-color: var(--card-official); }

.difficulty-badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 4px 12px;
  border-radius: 100px;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  width: fit-content;
}
.difficulty-badge--high    { background: var(--card-recall-dim); color: var(--card-recall); }
.difficulty-badge--medium  { background: var(--card-lecture-dim); color: var(--card-lecture); }
.difficulty-badge--official { background: var(--card-official-dim); color: var(--card-official); }

.quiz-card-stats {
  display: flex;
  gap: var(--spacing-sm);
  font-size: 0.8rem;
  color: var(--text-secondary);
}

/* ── Compact chooser cards ────────────────────────────────────── */
.chooser-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
  max-width: 960px;
}

.chooser-card {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 18px;
  border-radius: var(--radius-lg, 12px);
  background: var(--bg-card);
  border: 1px solid var(--border);
  cursor: pointer;
  transition: transform 0.12s, box-shadow 0.15s, border-color 0.15s;
}
.chooser-card:hover {
  transform: translateX(4px);
  background: var(--bg-card-hover);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.12);
  border-color: var(--card-accent, var(--accent));
}

.chooser-card__icon {
  flex-shrink: 0;
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.6rem;
  border-radius: 10px;
  background: color-mix(in srgb, var(--card-accent, var(--accent)) 10%, transparent);
}
.chooser-card__icon svg {
  width: 22px;
  height: 22px;
  stroke: var(--card-accent, var(--text-primary));
}

.chooser-card__body {
  flex: 1;
  min-width: 0;
}

.chooser-card__title {
  font-size: 0.95rem;
  font-weight: 650;
  color: var(--text-primary);
  line-height: 1.2;
}

.chooser-card__desc {
  font-size: 0.78rem;
  color: var(--text-secondary);
  margin-top: 2px;
  line-height: 1.3;
}

.chooser-card__meta {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-top: 4px;
  font-size: 0.72rem;
  color: var(--text-muted, var(--text-secondary));
}

.chooser-card__diff {
  margin-left: 6px;
  padding: 1px 7px;
  border-radius: 100px;
  font-size: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.03em;
}
.chooser-card__diff--med {
  background: var(--card-lecture-dim);
  color: var(--card-lecture);
}
.chooser-card__diff--hard {
  background: var(--card-recall-dim);
  color: var(--card-recall);
}
.chooser-card__diff--official {
  background: var(--card-official-dim);
  color: var(--card-official);
}

.chooser-card__arrow {
  flex-shrink: 0;
  font-size: 1.4rem;
  color: var(--text-muted, var(--text-secondary));
  opacity: 0.4;
  transition: opacity 0.12s, transform 0.12s;
}
.chooser-card:hover .chooser-card__arrow {
  opacity: 0.8;
  transform: translateX(2px);
}

/* Mobile: collapse chooser grid back to a single column */
@media (max-width: 767px) {
  .chooser-grid {
    grid-template-columns: 1fr;
    max-width: 100%;
  }
  .chooser-card {
    padding: 12px 14px;
  }
}

/* ── Quiz chooser: master-detail rail + detail panel ─────────── */
.qc-layout {
  display: grid;
  grid-template-columns: minmax(280px, 320px) minmax(480px, 1fr);
  gap: 24px;
  width: 100%;
  max-width: none;
  margin: 0;
  align-items: start;
}

/* Rail (master list of 5 quiz types) */
.qc-rail {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 12px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
  position: sticky;
  top: 20px;
}
.qc-rail-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.qc-rail-group + .qc-rail-group {
  margin-top: 6px;
  padding-top: 10px;
  border-top: 1px solid var(--border-light);
}
.qc-rail-label {
  font-size: 0.64rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-muted);
  padding: 8px 12px 4px 12px;
}

.qc-rail-item {
  --card-color: var(--accent);
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 14px;
  border-radius: 10px;
  cursor: pointer;
  transition: background 0.15s, transform 0.12s, border-color 0.15s;
  border: 1px solid transparent;
  text-align: left;
  background: transparent;
  width: 100%;
  font-family: inherit;
  color: inherit;
}
.qc-rail-item:hover {
  background: var(--bg-card-hover);
}
.qc-rail-item.active {
  background: color-mix(in srgb, var(--card-color) 12%, transparent);
  border-color: color-mix(in srgb, var(--card-color) 30%, transparent);
}

.qc-rail-item__icon {
  flex-shrink: 0;
  width: 36px;
  height: 36px;
  border-radius: 9px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.05rem;
  background: color-mix(in srgb, var(--card-color) 16%, transparent);
  border: 1px solid color-mix(in srgb, var(--card-color) 28%, transparent);
}
.qc-rail-item__icon svg {
  width: 18px;
  height: 18px;
  fill: none;
  stroke: var(--card-color);
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.qc-rail-item__body {
  flex: 1;
  min-width: 0;
}
.qc-rail-item__title {
  font-size: 0.84rem;
  font-weight: 650;
  color: var(--text-primary);
  line-height: 1.2;
  display: flex;
  align-items: center;
  gap: 6px;
}
.qc-rail-item.active .qc-rail-item__title {
  color: var(--card-color);
}
.qc-rail-item__sub {
  font-size: 0.68rem;
  color: var(--text-muted);
  margin-top: 3px;
  font-variant-numeric: tabular-nums;
}
.qc-rail-item__dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--card-color);
  flex-shrink: 0;
  margin-left: auto;
  box-shadow: 0 0 8px color-mix(in srgb, var(--card-color) 60%, transparent);
}

.qc-rail-item--lecture  { --card-color: var(--card-lecture); }
.qc-rail-item--expert   { --card-color: var(--card-expert); }
.qc-rail-item--recall   { --card-color: var(--card-recall); }
.qc-rail-item--official { --card-color: var(--card-official); }
.qc-rail-item--rohan    { --card-color: var(--card-rohan); }
.qc-rail-item--playground { --card-color: var(--card-playground); }

/* Detail panel (the rich content for the currently-selected rail item) */
.qc-detail {
  --card-color: var(--accent);
  padding: 28px 32px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
  min-width: 0;
  min-height: 240px;
}
.qc-detail--lecture  { --card-color: var(--card-lecture); }
.qc-detail--expert   { --card-color: var(--card-expert); }
.qc-detail--recall   { --card-color: var(--card-recall); }
.qc-detail--official { --card-color: var(--card-official); }
.qc-detail--rohan    { --card-color: var(--card-rohan); }
.qc-detail--playground { --card-color: var(--card-playground); }

html[data-theme="glass"] .qc-rail,
html[data-theme="glass"] .qc-detail {
  border-color: rgba(214, 238, 239, 0.16);
  background: rgba(16, 29, 28, 0.62);
  box-shadow: 0 16px 42px rgba(1, 8, 10, 0.13), inset 0 1px 0 rgba(255, 255, 255, 0.10);
  backdrop-filter: blur(10px) saturate(108%);
  -webkit-backdrop-filter: blur(10px) saturate(108%);
}

html[data-theme="glass"] .qc-rail-item.active {
  background: color-mix(in srgb, var(--card-color) 11%, rgba(255, 255, 255, 0.018));
  border-color: color-mix(in srgb, var(--card-color) 24%, transparent);
}

html[data-theme="glass"] .qc-rail-item__icon,
html[data-theme="glass"] .qc-detail-icon {
  background: color-mix(in srgb, var(--card-color) 14%, rgba(255, 255, 255, 0.018));
  border-color: color-mix(in srgb, var(--card-color) 24%, transparent);
}

.qc-detail-header {
  display: flex;
  align-items: flex-start;
  gap: 20px;
  margin-bottom: 8px;
}
.qc-detail-icon {
  flex-shrink: 0;
  width: 72px;
  height: 72px;
  border-radius: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: color-mix(in srgb, var(--card-color) 16%, transparent);
  border: 1px solid color-mix(in srgb, var(--card-color) 28%, transparent);
}
.qc-detail-icon svg {
  width: 38px;
  height: 38px;
  fill: none;
  stroke: var(--card-color);
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.qc-detail-title-block {
  flex: 1;
  min-width: 0;
}
/* Tag badges (purpose + difficulty) */
.qc-detail-tags {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  margin-bottom: 6px;
}
.qc-tag {
  display: inline-flex;
  align-items: center;
  font-size: 0.6rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 3px 9px;
  border-radius: 100px;
  line-height: 1.2;
}
.qc-tag--purpose {
  background: color-mix(in srgb, var(--card-color) 22%, transparent);
  color: var(--card-color);
  border: 1px solid color-mix(in srgb, var(--card-color) 35%, transparent);
}
.qc-tag--difficulty {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-light);
}
.qc-tag--coming-soon {
  background: rgba(148, 163, 184, 0.15);
  color: #94a3b8;
  border: 1px solid rgba(148, 163, 184, 0.3);
}
.qc-tag--author {
  background: rgba(168, 85, 247, 0.15);
  color: #c084fc;
  border: 1px solid rgba(168, 85, 247, 0.3);
}

/* ── Achievement Badges ──────────────────────────────────── */
.ach-badge-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(90px, 1fr));
  gap: 8px;
}
.ach-badge {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 10px 8px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-secondary);
  transition: transform 0.15s, border-color 0.2s, box-shadow 0.2s;
  text-align: center;
}
.ach-badge--earned {
  border-color: var(--accent);
  background: var(--accent-dim);
  cursor: default;
}
.ach-badge--earned:hover {
  transform: scale(1.05);
}
.ach-badge--locked {
  opacity: 0.55;
}
.ach-badge--bronze { border-color: #cd7f32; }
.ach-badge--silver { border-color: #a8a9ad; }
.ach-badge--gold   { border-color: #ffd700; box-shadow: 0 0 8px rgba(255, 215, 0, 0.15); }
.ach-badge--diamond { border-color: #b9f2ff; box-shadow: 0 0 12px rgba(185, 242, 255, 0.2); }
.ach-badge-icon {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
}
.ach-badge-icon svg {
  width: 40px;
  height: 40px;
}
.ach-badge-label {
  font-size: 0.68rem;
  font-weight: 650;
  color: var(--text-primary);
  line-height: 1.2;
}
.ach-badge--locked .ach-badge-label {
  color: var(--text-muted);
}
.ach-badge-tier {
  font-size: 0.6rem;
  color: var(--text-muted);
  font-weight: 500;
}
.ach-badge-progress {
  width: 100%;
  height: 3px;
  background: var(--border);
  border-radius: 2px;
  overflow: hidden;
  margin-top: 2px;
}
.ach-badge-progress-fill {
  height: 100%;
  border-radius: 2px;
  background: var(--accent);
  transition: width 0.3s ease;
}
.qc-detail-title {
  margin: 0;
  font-size: 1.45rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--text-primary);
}
.qc-detail-desc {
  margin: 6px 0 0 0;
  font-size: 0.92rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* Stats grid (4-up with tinted background) */
.qc-stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin: 24px 0;
  padding: 20px;
  background: var(--bg-input);
  border-radius: 12px;
  border: 1px solid var(--border);
}
.qc-stat-block {
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.qc-stat-block__value {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--text-primary);
  font-variant-numeric: tabular-nums;
  line-height: 1;
}
.qc-stat-block__value .qc-unit {
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-left: 2px;
}
.qc-stat-block__label {
  font-size: 0.72rem;
  color: var(--text-secondary);
  font-weight: 500;
}
.qc-stat-block--accent .qc-stat-block__value { color: var(--card-color); }

/* Overall progress bar */
.qc-progress-wrap {
  margin-bottom: 24px;
}
.qc-progress-wrap-label {
  display: flex;
  justify-content: space-between;
  font-size: 0.75rem;
  color: var(--text-secondary);
  font-weight: 600;
  margin-bottom: 6px;
  font-variant-numeric: tabular-nums;
}
.qc-progress-bar-big {
  height: 8px;
  background: var(--bg-input);
  border-radius: 100px;
  overflow: hidden;
  border: 1px solid var(--border);
}
.qc-progress-fill-big {
  height: 100%;
  background: linear-gradient(90deg, var(--card-color), color-mix(in srgb, var(--card-color) 60%, #fff));
  border-radius: 100px;
  transition: width 0.3s ease;
}

/* Sessions section (solves the multi-resume problem) */
.qc-sessions-section {
  margin-bottom: 24px;
}
.qc-section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
}
.qc-section-title {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: 0.02em;
  text-transform: uppercase;
}
.qc-section-count {
  font-size: 0.68rem;
  padding: 2px 8px;
  border-radius: 100px;
  background: color-mix(in srgb, var(--card-color) 18%, transparent);
  color: var(--card-color);
  font-weight: 700;
}
.qc-session-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.qc-session-item {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 16px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s, transform 0.12s;
  text-align: left;
  font-family: inherit;
  color: inherit;
  width: 100%;
}
.qc-session-item:hover {
  background: var(--bg-card-hover);
  border-color: color-mix(in srgb, var(--card-color) 50%, transparent);
}
.qc-session-item__main {
  flex: 1;
  min-width: 0;
}
.qc-session-item__topic {
  font-size: 0.86rem;
  font-weight: 650;
  color: var(--text-primary);
  margin-bottom: 3px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.qc-session-item__meta {
  font-size: 0.7rem;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
}
.qc-session-item__progress {
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 4px;
  min-width: 90px;
}
.qc-session-item__percent {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--card-color);
  font-variant-numeric: tabular-nums;
}
.qc-session-item__bar {
  width: 80px;
  height: 4px;
  background: var(--bg-input);
  border-radius: 100px;
  overflow: hidden;
}
.qc-session-item__bar-fill {
  height: 100%;
  background: var(--card-color);
  border-radius: 100px;
}
/* Session delete button */
.qc-session-item__delete {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  padding: 0;
  background: transparent;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.15s, background 0.15s;
  color: var(--text-muted);
}
.qc-session-item__delete svg {
  width: 14px;
  height: 14px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}
.qc-session-item:hover .qc-session-item__delete {
  opacity: 1;
}
.qc-session-item__delete:hover {
  background: var(--error-dim);
  color: var(--error);
}

/* Session resume button */
.qc-session-item__resume-btn {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  padding: 0;
  background: transparent;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  color: var(--text-muted);
  font-size: 1.1rem;
  opacity: 0.5;
  transition: opacity 0.15s;
  font-family: inherit;
}
.qc-session-item:hover .qc-session-item__resume-btn {
  opacity: 1;
}

/* "Show all" link for session cap overflow */
.qc-sessions-show-all {
  display: block;
  width: 100%;
  padding: 10px;
  margin-top: 6px;
  background: transparent;
  border: 1px dashed var(--border);
  border-radius: 8px;
  color: var(--text-secondary);
  font-size: 0.78rem;
  font-weight: 600;
  text-align: center;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
  font-family: inherit;
}
.qc-sessions-show-all:hover {
  background: var(--bg-card);
  color: var(--text-primary);
}

/* Undo toast (fixed bottom-center) */
.qc-undo-toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 20px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
  color: var(--text-primary);
  font-size: 0.85rem;
  font-weight: 500;
  z-index: 9000;
  opacity: 0;
  transition: opacity 0.3s, transform 0.3s;
}
.qc-undo-toast.visible {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}
.qc-undo-btn {
  padding: 4px 12px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 6px;
  font-size: 0.78rem;
  font-weight: 700;
  cursor: pointer;
  transition: background 0.15s;
  font-family: inherit;
}
.qc-undo-btn:hover {
  background: var(--accent-hover);
}

/* Empty state when there are no in-progress sessions */
.qc-empty-state {
  padding: 24px 20px;
  text-align: center;
  background: var(--bg-card);
  border: 1px dashed var(--border);
  border-radius: 10px;
  color: var(--text-muted);
  font-size: 0.82rem;
}

/* Action buttons below the sessions list */
.qc-action-row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}
.qc-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 11px 22px;
  border-radius: 10px;
  font-size: 0.88rem;
  font-weight: 650;
  cursor: pointer;
  border: 1px solid transparent;
  text-decoration: none;
  transition: background 0.15s, border-color 0.15s, transform 0.12s;
  font-family: inherit;
}
.qc-btn svg {
  width: 16px;
  height: 16px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2.2;
  stroke-linecap: round;
  stroke-linejoin: round;
}
.qc-btn--primary {
  background: var(--card-color);
  color: #fff;
  border-color: var(--card-color);
}
.qc-btn--primary:hover {
  background: color-mix(in srgb, var(--card-color) 85%, #fff);
  transform: translateY(-1px);
}
.qc-btn--secondary {
  background: var(--bg-card);
  color: var(--text-primary);
  border-color: var(--border);
}
.qc-btn--secondary:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-light);
}

/* Skeleton loading state (before stats come back) */
.qc-skeleton {
  color: var(--text-muted);
  font-size: 0.82rem;
  min-height: 100%;
  padding: 20px 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Mobile: rail becomes a horizontal scrollable tab row at the top */
@media (max-width: 767px) {
  .qc-layout {
    grid-template-columns: 1fr;
    gap: 12px;
  }

  /* Vertical stacked cards instead of horizontal scroll */
  .qc-rail {
    flex-direction: column;
    position: static;
    padding: 8px;
    gap: 4px;
    overflow-x: visible;
  }
  .qc-rail-group { gap: 4px; }
  .qc-rail-group + .qc-rail-group { margin-top: 4px; padding-top: 8px; }
  .qc-rail-item {
    flex-shrink: 0;
    padding: 10px 14px;
    width: 100%;
  }
  .qc-rail-item__icon {
    width: 32px;
    height: 32px;
  }
  .qc-rail-item__icon svg {
    width: 18px;
    height: 18px;
  }
  .qc-rail-item__sub { display: none; }

  /* Detail panel */
  .qc-detail {
    padding: 20px 14px;
  }
  .qc-stats-grid {
    grid-template-columns: repeat(2, 1fr);
    padding: 14px;
  }
  .qc-detail-header {
    gap: 14px;
  }
  .qc-detail-icon {
    width: 56px;
    height: 56px;
  }
  .qc-detail-icon svg {
    width: 28px;
    height: 28px;
  }
  .qc-detail-title { font-size: 1.2rem; }
  .qc-session-item__progress { min-width: 70px; }
  .qc-session-item__bar { width: 60px; }
  .qc-session-item__delete { opacity: 1; }
  .qc-session-item__resume-btn { opacity: 1; }
}

.construction-label {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  border-radius: 100px;
  background: var(--card-expert-dim);
  color: var(--text-muted);
  font-size: 0.8rem;
  font-weight: 600;
  width: fit-content;
}

/* Badges */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 4px 10px;
  border-radius: 100px;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  white-space: nowrap;
  max-width: 220px;
  overflow: hidden;
  text-overflow: ellipsis;
}

.badge-high { background: var(--error-dim); color: var(--error); }
.badge-medium-high { background: var(--warning-dim); color: var(--warning); }
.badge-medium { background: var(--accent-dim); color: var(--accent); }
.badge-low { background: rgba(107, 114, 128, 0.2); color: var(--text-secondary); }

.badge-reinforcement { background: var(--success-dim); color: var(--success); }
.badge-moderate { background: var(--warning-dim); color: var(--warning); }
.badge-hard { background: var(--error-dim); color: var(--error); }

/* Dashboard expand/collapse wrapper + button */
.dash-expand-wrap {
  position: relative;
  margin-top: -50px;
  padding-top: 50px;
  pointer-events: none;
}

.dash-expand-wrap::before {
  content: '';
  position: absolute;
  top: 0;
  left: -20px;
  right: -20px;
  height: 50px;
  background: linear-gradient(to bottom, transparent, var(--bg-card));
  pointer-events: none;
  z-index: 1;
}

.dash-expand-wrap > .dash-expand-btn {
  pointer-events: auto;
  position: relative;
  z-index: 2;
}

.dash-expand-wrap.expanded {
  margin-top: 0;
  padding-top: 0;
}

.dash-expand-wrap.expanded::before {
  display: none;
}

.dash-expand-btn {
  display: block;
  width: 100%;
  margin-top: var(--spacing-sm);
  padding: 10px;
  border: 1px solid var(--accent-dim);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--accent);
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  cursor: pointer;
  transition: all 0.2s ease;
}

.dash-expand-btn:hover {
  background: var(--accent-dim);
  box-shadow: 0 0 12px var(--accent-dim), 0 0 4px var(--accent-dim);
}

/* Progress bar */
.progress-bar {
  width: 100%;
  height: 6px;
  background: var(--bg-secondary);
  border-radius: 3px;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 3px;
  transition: width 0.4s ease;
}

/* Option buttons (quiz) */
.option-btn {
  display: flex;
  align-items: flex-start;
  gap: var(--spacing-md);
  width: 100%;
  text-align: left;
  padding: var(--spacing-md);
  background: var(--bg-secondary);
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-size: 0.95rem;
  line-height: 1.5;
  transition: all var(--transition);
  cursor: pointer;
}

.option-btn:hover:not(.option-disabled) {
  border-color: var(--accent);
  background: var(--accent-dim);
}

.option-btn.option-selected {
  border-color: var(--accent);
  background: var(--accent-dim);
}

/* Keyboard focus must read as a focus ring, not as the green selection
   fill — sighted keyboard users couldn't tell focus from selection
   otherwise. Only applies to keyboard / programmatic focus, not mouse. */
.option-btn:focus-visible:not(.option-disabled) {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}
.option-btn:focus-visible:not(.option-selected):not(.option-disabled) {
  background: var(--bg-secondary);
  border-color: var(--border);
}

.option-btn.option-correct {
  border-color: var(--success);
  background: var(--success-dim);
  cursor: default;
}

.option-btn.option-incorrect {
  border-color: var(--error);
  background: var(--error-dim);
  cursor: default;
}

.option-btn.option-disabled {
  cursor: default;
  opacity: 0.8;
}
.option-btn.option-struck {
  opacity: 0.35;
  text-decoration: line-through;
  text-decoration-color: var(--text-muted);
}

.option-btn .option-letter {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--border);
  font-weight: 600;
  font-size: 0.85rem;
  flex-shrink: 0;
}

.option-btn.option-selected .option-letter { background: var(--accent); color: #fff; }
.option-btn.option-correct .option-letter { background: var(--success); color: #0f1117; }
.option-btn.option-incorrect .option-letter { background: var(--error); color: #0f1117; }

/* Feedback panel */
.feedback-panel {
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  overflow: hidden;
}

.feedback-header {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  padding: var(--spacing-md) var(--spacing-lg);
  font-weight: 600;
}

.feedback-correct { background: var(--success-dim); color: var(--success); }
.feedback-incorrect { background: var(--error-dim); color: var(--error); }

.feedback-body {
  padding: var(--spacing-lg);
  background: var(--bg-card);
}

.feedback-explanation {
  padding: var(--spacing-md);
  margin-bottom: var(--spacing-sm);
  border-radius: var(--radius-sm);
  background: var(--bg-secondary);
}

.feedback-explanation.explanation-correct {
  border-left-color: var(--success);
}

/* Peer-percentile badge (mastery model) — cohort first-attempt accuracy under
   the explanation. Social proof from the item ratings; only shown at n>=5. */
.peer-badge {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 4px 10px;
  padding: var(--spacing-sm) var(--spacing-md);
  margin-bottom: var(--spacing-sm);
  border-radius: var(--radius-sm);
  background: var(--accent-dim, color-mix(in srgb, var(--accent) 10%, transparent));
  border-left: 3px solid var(--accent);
}
.peer-badge__avg { font-size: 0.95rem; color: var(--text-primary); }
.peer-badge__avg strong { color: var(--accent); }
.peer-badge__you { font-size: 0.85rem; color: var(--text-secondary); }

.feedback-explanation h4 {
  margin-bottom: var(--spacing-xs);
  color: var(--text-secondary);
}

.references-block {
  margin-top: var(--spacing-md);
  padding: var(--spacing-md);
  background: var(--bg-secondary);
  border-radius: var(--radius-sm);
}

.references-label {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--spacing-sm);
}

.references-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.reference-chip {
  display: inline-block;
  padding: 4px 12px;
  font-size: 0.85rem;
  line-height: 1.5;
  background: transparent;
  color: var(--accent);
  border: 1.5px solid var(--accent);
  border-radius: 999px;
  white-space: nowrap;
  font-weight: 500;
}

/* Filter pills */
.filter-pills {
  display: flex;
  gap: var(--spacing-sm);
  flex-wrap: wrap;
}

@media (max-width: 767px) {
  .filter-pills-scroll {
    flex-wrap: nowrap;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    padding-bottom: 2px;
  }
  .filter-pills-scroll::-webkit-scrollbar { display: none; }
  .filter-pills-scroll .filter-pill {
    flex-shrink: 0;
  }
}

.filter-pill {
  padding: var(--spacing-xs) var(--spacing-md);
  border-radius: 100px;
  font-size: 0.85rem;
  font-weight: 500;
  background: var(--bg-card);
  color: var(--text-secondary);
  border: 1px solid var(--border);
  cursor: pointer;
  transition: all var(--transition);
}

.filter-pill:hover { border-color: var(--accent); color: var(--text-primary); }
.filter-pill.active { background: var(--accent); color: #fff; border-color: var(--accent); }

/* Topic chips */
.topic-chip {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-xs) var(--spacing-md);
  border-radius: 100px;
  font-size: 0.85rem;
  background: var(--bg-card);
  color: var(--text-secondary);
  border: 1px solid var(--border);
  cursor: pointer;
  transition: all var(--transition);
}

.topic-chip:hover { border-color: var(--accent); }
.topic-chip.selected { background: var(--accent-dim); color: var(--accent); border-color: var(--accent); }

/* Score display */
.score-display {
  display: flex;
  align-items: baseline;
  gap: var(--spacing-xs);
}

.score-display .score-current {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent);
}

.score-display .score-total {
  font-size: 1rem;
  color: var(--text-muted);
}

/* Flag button */
.flag-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-xs) var(--spacing-sm);
  background: transparent;
  color: var(--text-muted);
  font-size: 0.85rem;
  border-radius: var(--radius-sm);
  transition: all var(--transition);
}

.flag-btn:hover { color: var(--warning); }
.flag-btn.flagged { color: var(--warning); }

/* Toast — confirmation popup that appears after an action.
   z-index must sit above the floating Ask Aura chat FAB (z-index 9999 in
   js/components/kb-chat.js) since both anchor bottom-right and the popup
   would otherwise be clipped. */
.toast {
  position: fixed;
  bottom: var(--spacing-lg);
  right: var(--spacing-lg);
  padding: var(--spacing-md) var(--spacing-lg);
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-size: 0.9rem;
  z-index: 10000;
  animation: slideUp 0.3s ease;
}

.toast-success { border-left: 3px solid var(--success); }
.toast-error { border-left: 3px solid var(--error); }

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

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

/* Mobile: toast at top (avoids keyboard overlap) */
@media (max-width: 767px) {
  .toast {
    bottom: auto;
    top: calc(var(--nav-height) + var(--spacing-sm));
    right: var(--spacing-sm);
    left: var(--spacing-sm);
    animation: slideDown 0.3s ease;
  }
}

/* Loading spinner */
.spinner,
.sn-spinner {
  display: inline-block;
  width: 34px;
  height: 34px;
  flex: 0 0 auto;
  background: url("../img/loaders/aura-ring.svg") center / contain no-repeat;
  border: 0;
  border-radius: 0;
  color: var(--accent);
  filter: drop-shadow(0 0 10px color-mix(in srgb, var(--accent) 20%, transparent));
}

@media (prefers-reduced-motion: reduce) {
  .spinner,
  .sn-spinner {
    background: none;
    border: 3px solid color-mix(in srgb, var(--accent) 18%, transparent);
    border-top-color: var(--accent);
    border-radius: 50%;
    filter: none;
  }
}

.loading-container {
  display: flex;
  justify-content: center;
  align-items: center;
  padding: var(--spacing-2xl);
}

/* Empty state */
.empty-state {
  text-align: center;
  padding: var(--spacing-2xl);
  color: var(--text-muted);
}

.empty-state h3 {
  margin-bottom: var(--spacing-sm);
  color: var(--text-secondary);
}

/* Mobile: larger tap targets (WCAG 44px minimum) */
@media (max-width: 767px) {
  .btn {
    min-height: 44px;
    padding: 12px var(--spacing-lg);
  }
  .btn-sm {
    min-height: 44px;
    padding: 10px var(--spacing-md);
  }
  .btn-lg {
    min-height: 44px;
  }
  .filter-pill,
  .topic-chip {
    min-height: 44px;
    padding: 10px var(--spacing-md);
  }
  .flag-btn {
    min-height: 44px;
    padding: var(--spacing-sm) var(--spacing-md);
  }
  .score-display .score-current {
    font-size: 1.1rem;
  }
  .score-display .score-total {
    font-size: 0.85rem;
  }
  .option-btn {
    padding: 10px var(--spacing-md);
    gap: var(--spacing-sm);
    font-size: 0.9rem;
  }
  .option-btn .option-letter {
    width: 24px;
    height: 24px;
    font-size: 0.7rem;
  }
  .feedback-header {
    padding: var(--spacing-sm) var(--spacing-md);
  }
  .feedback-body {
    padding: var(--spacing-md);
  }
  .feedback-explanation {
    padding: var(--spacing-sm) var(--spacing-md);
  }
}

/* Zoom-out hint banner (first-visit, narrow-desktop, sidebar-layout only) */
.zoom-banner {
  position: fixed;
  top: 12px;
  left: 50%;
  display: flex;
  align-items: center;
  gap: 12px;
  max-width: calc(100vw - 32px);
  padding: 10px 14px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-soft);
  color: var(--text-primary);
  font-size: 0.85rem;
  line-height: 1.4;
  z-index: 9000;
  animation: zoom-banner-in 0.3s ease-out;
  transform: translateX(-50%);
}

.zoom-banner--display-fit {
  align-items: center;
}

.zoom-banner kbd {
  display: inline-block;
  min-width: 20px;
  padding: 2px 6px;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-align: center;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text-primary);
}

.zoom-banner__actions {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  flex-shrink: 0;
}

.zoom-banner__layout {
  min-height: 28px;
  padding: 5px 10px;
  border: 1px solid color-mix(in srgb, var(--accent) 22%, var(--border));
  border-radius: 999px;
  background: var(--accent-dim);
  color: var(--accent);
  font: inherit;
  font-size: 0.78rem;
  font-weight: 750;
  cursor: pointer;
}

.zoom-banner__layout:hover {
  background: color-mix(in srgb, var(--accent) 14%, var(--bg-card));
}

.zoom-banner__close {
  flex-shrink: 0;
  background: transparent;
  border: 0;
  color: var(--text-secondary);
  font-size: 1.25rem;
  line-height: 1;
  cursor: pointer;
  padding: 0 4px;
}

.zoom-banner__close:hover {
  color: var(--text-primary);
}

.quota-banner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-sm);
  margin: 0 0 var(--spacing-md);
  padding: 10px 12px;
  color: var(--text-primary);
  font-size: 0.9rem;
  line-height: 1.45;
  background: var(--warning-dim);
  border: 1px solid color-mix(in srgb, var(--warning) 48%, var(--border));
  border-radius: var(--radius-sm);
}

.quota-banner__close {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: transparent;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-size: 1.15rem;
  line-height: 1;
  cursor: pointer;
}

.quota-banner__close:hover {
  color: var(--text-primary);
  border-color: color-mix(in srgb, var(--warning) 38%, var(--border));
  background: color-mix(in srgb, var(--warning) 10%, transparent);
}

.zoom-banner--hiding {
  opacity: 0;
  transform: translate(-50%, -8px);
  transition: opacity 0.2s, transform 0.2s;
}

@keyframes zoom-banner-in {
  from { opacity: 0; transform: translate(-50%, -8px); }
  to { opacity: 1; transform: translate(-50%, 0); }
}

@media (max-width: 767px) {
  .zoom-banner {
    top: auto;
    bottom: calc(78px + env(safe-area-inset-bottom, 0px));
    flex-wrap: wrap;
    justify-content: center;
    width: calc(100vw - 24px);
    text-align: center;
  }

  .zoom-banner__text {
    flex-basis: 100%;
  }

  .quota-banner {
    align-items: flex-start;
  }
}

/* Glass Mode shared component surfaces */
html[data-theme="glass"] .card,
html[data-theme="glass"] .chooser-card,
html[data-theme="glass"] .qc-rail,
html[data-theme="glass"] .qc-detail,
html[data-theme="glass"] .qc-stats-grid,
html[data-theme="glass"] .qc-session-item,
html[data-theme="glass"] .qc-empty-state {
  border-color: var(--glass-panel-border);
  background:
    linear-gradient(135deg, rgba(255, 255, 255, 0.038), rgba(255, 255, 255, 0.006) 42%, rgba(100, 199, 167, 0.018) 76%, rgba(255, 255, 255, 0.026)),
    var(--glass-panel-bg);
  box-shadow: 0 16px 42px rgba(1, 8, 10, 0.13), inset 0 1px 0 var(--glass-panel-highlight);
  backdrop-filter: blur(10px) saturate(108%);
  -webkit-backdrop-filter: blur(10px) saturate(108%);
}

html[data-theme="glass"] .qc-detail,
html[data-theme="glass"] .qc-rail {
  background:
    linear-gradient(135deg, rgba(255, 255, 255, 0.040), rgba(255, 255, 255, 0.008) 42%, rgba(100, 199, 167, 0.020) 76%, rgba(255, 255, 255, 0.028)),
    var(--glass-panel-bg-strong);
}

html[data-theme="glass"] .btn-primary,
html[data-theme="glass"] .qc-btn--primary {
  background: linear-gradient(135deg, color-mix(in srgb, var(--accent) 92%, #fff), var(--accent));
  color: #09201a;
  border-color: color-mix(in srgb, var(--accent) 72%, transparent);
  box-shadow: 0 12px 26px color-mix(in srgb, var(--accent) 16%, transparent), inset 0 1px 0 rgba(255, 255, 255, 0.22);
}

html[data-theme="glass"] .btn-secondary,
html[data-theme="glass"] .qc-btn--secondary,
html[data-theme="glass"] .filter-pill,
html[data-theme="glass"] .chooser-card {
  border-color: rgba(214, 238, 229, 0.16);
  background: rgba(255, 255, 255, 0.026);
}

html[data-theme="glass"] .filter-pill.active {
  background: color-mix(in srgb, var(--accent) 76%, rgba(255, 255, 255, 0.08));
  color: #082018;
  border-color: color-mix(in srgb, var(--accent) 70%, transparent);
}