/* ============================================================================
   SURFACE MODES & ACCENT PALETTE ENGINE
   ============================================================================ */
:root,
html[data-theme="dark"] {
  --bg-app: #0b1120;
  --bg-header: linear-gradient(180deg, #111827 0%, #0b1120 100%);
  --bg-surface: #111827;
  --bg-card: #162033;
  --bg-elevated: #1e293b;
  --bg-console: #0d1424;
  --border-subtle: #26354d;
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --shadow-card: 0 10px 30px -10px rgba(0, 0, 0, 0.55);
  --shadow-popover: 0 18px 40px -8px rgba(0, 0, 0, 0.7);
}

html[data-theme="light"] {
  --bg-app: #f8fafc;
  --bg-header: linear-gradient(180deg, #ffffff 0%, #f1f5f9 100%);
  --bg-surface: #f1f5f9;
  --bg-card: #ffffff;
  --bg-elevated: #e2e8f0;
  --bg-console: #f8fafc;
  --border-subtle: #cbd5e1;
  --text-primary: #0f172a;
  --text-secondary: #334155;
  --text-muted: #64748b;
  --shadow-card: 0 8px 24px -8px rgba(15, 23, 42, 0.08);
  --shadow-popover: 0 18px 38px -8px rgba(15, 23, 42, 0.18);
}

/* 5 Custom Accent Palettes */
:root,
html[data-accent="cyan"] {
  --accent-primary: #0ea5e9;
  --accent-hover: #38bdf8;
  --accent-glow: rgba(14, 165, 233, 0.35);
  --accent-soft-bg: rgba(14, 165, 233, 0.14);
  --accent-soft: rgba(14, 165, 233, 0.14);
  --accent-text: #38bdf8;
}
html[data-theme="light"][data-accent="cyan"] {
  --accent-text: #0284c7;
}

html[data-accent="crimson"] {
  --accent-primary: #be123c;
  --accent-hover: #f43f5e;
  --accent-glow: rgba(244, 63, 94, 0.35);
  --accent-soft-bg: rgba(244, 63, 94, 0.15);
  --accent-soft: rgba(244, 63, 94, 0.15);
  --accent-text: #fb7185;
}
html[data-theme="light"][data-accent="crimson"] {
  --accent-text: #be123c;
}

html[data-accent="emerald"] {
  --accent-primary: #059669;
  --accent-hover: #10b981;
  --accent-glow: rgba(16, 185, 129, 0.35);
  --accent-soft-bg: rgba(16, 185, 129, 0.15);
  --accent-soft: rgba(16, 185, 129, 0.15);
  --accent-text: #34d399;
}
html[data-theme="light"][data-accent="emerald"] {
  --accent-text: #047857;
}

html[data-accent="indigo"] {
  --accent-primary: #4f46e5;
  --accent-hover: #6366f1;
  --accent-glow: rgba(99, 102, 241, 0.35);
  --accent-soft-bg: rgba(99, 102, 241, 0.15);
  --accent-soft: rgba(99, 102, 241, 0.15);
  --accent-text: #818cf8;
}
html[data-theme="light"][data-accent="indigo"] {
  --accent-text: #4338ca;
}

html[data-accent="amber"] {
  --accent-primary: #d97706;
  --accent-hover: #f59e0b;
  --accent-glow: rgba(245, 158, 11, 0.35);
  --accent-soft-bg: rgba(245, 158, 11, 0.15);
  --accent-soft: rgba(245, 158, 11, 0.15);
  --accent-text: #fbbf24;
}
html[data-theme="light"][data-accent="amber"] {
  --accent-text: #b45309;
}

:root {
  --border-focus: var(--accent-hover);
  --success: #10b981;
  --success-bg: rgba(16, 185, 129, 0.13);
  --warning: #f59e0b;
  --warning-bg: rgba(245, 158, 11, 0.14);
  --danger: #ef4444;
  --danger-bg: rgba(239, 68, 68, 0.13);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'SFMono-Regular', Menlo, Monaco, Consolas, monospace;
}

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

body {
  background-color: var(--bg-app);
  color: var(--text-primary);
  font-family: var(--font-sans);
  line-height: 1.55;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background-color 0.2s ease, color 0.2s ease;
}

/* TOP HEADER */
.app-header {
  background: var(--bg-header);
  border-bottom: 1px solid var(--border-subtle);
  padding: 0.8rem 1.5rem 0.65rem;
  position: sticky;
  top: 0;
  z-index: 50;
}

.header-inner {
  max-width: 1440px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.85rem;
}

.brand-block {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.brand-icon {
  width: 42px;
  height: 42px;
  border-radius: 10px;
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-hover));
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 1.05rem;
  color: #fff;
  letter-spacing: -0.5px;
  box-shadow: 0 4px 14px var(--accent-glow);
}

.brand-title h1 {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
}

.brand-sub {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.75rem;
  color: var(--text-muted);
}

.source-badge {
  color: var(--accent-text);
  font-family: var(--font-mono);
  font-size: 0.72rem;
}

.header-controls,
.header-utilities {
  margin-left: auto;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
}

/* Second Header Row: Mode Selector Bar */
.mode-selector-bar {
  max-width: 1440px;
  margin: 0.65rem auto 0;
  padding-top: 0.6rem;
  border-top: 1px solid var(--border-subtle);
}

.mode-selector-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem;
}

.mode-bar-label {
  font-size: 0.76rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
}

.mode-bar-segments {
  flex-wrap: wrap;
}

.segmented-control {
  display: inline-flex;
  background: var(--bg-console);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 3px;
  gap: 2px;
}

.seg-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  font-size: 0.79rem;
  font-weight: 600;
  padding: 0.42rem 0.78rem;
  border-radius: 7px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.seg-btn:hover {
  color: var(--text-primary);
}

.seg-btn.active {
  background: var(--accent-primary);
  color: #fff;
  box-shadow: 0 2px 8px var(--accent-glow);
}

.btn-mode-toggle {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  color: var(--text-primary);
  padding: 0.45rem 0.82rem;
  border-radius: var(--radius-md);
  font-size: 0.79rem;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  transition: all 0.15s ease;
}

.btn-mode-toggle:hover:not(:disabled) {
  border-color: var(--accent-hover);
}

.btn-mode-toggle:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

.btn-mode-toggle.exam-active {
  background: var(--danger-bg);
  border-color: var(--danger);
  color: var(--danger);
}

.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  display: inline-block;
}

.practice-dot {
  background: var(--success);
  box-shadow: 0 0 8px var(--success);
}

.exam-dot {
  background: var(--danger);
  box-shadow: 0 0 8px var(--danger);
}

/* ============================================================================
   UPPER-RIGHT 🎨 THEME PICKER POPOVER
   ============================================================================ */
.theme-picker-wrapper {
  position: relative;
}

.theme-trigger-btn {
  border-color: var(--accent-primary);
  background: var(--accent-soft-bg);
}

.theme-popover {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  width: 290px;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-popover);
  padding: 0.95rem;
  z-index: 120;
  display: none;
  flex-direction: column;
  gap: 0.9rem;
}

.theme-popover.open {
  display: flex;
}

.theme-section-title {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  margin-bottom: 0.45rem;
}

.surface-mode-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.45rem;
}

.surface-mode-btn {
  background: var(--bg-console);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 0.5rem 0.55rem;
  color: var(--text-primary);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 2px;
  font-size: 0.78rem;
  font-weight: 600;
  transition: all 0.15s ease;
}

.surface-mode-btn small {
  font-size: 0.66rem;
  color: var(--text-muted);
  font-weight: 400;
}

.surface-mode-btn.active {
  border-color: var(--accent-primary);
  background: var(--accent-soft-bg);
}

.accent-swatch-list {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.accent-swatch-btn {
  background: var(--bg-console);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 0.45rem 0.65rem;
  color: var(--text-primary);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-size: 0.8rem;
  font-weight: 600;
  transition: all 0.15s ease;
}

.accent-swatch-btn:hover {
  border-color: var(--accent-hover);
}

.accent-swatch-btn.active {
  border-color: var(--accent-primary);
  background: var(--accent-soft-bg);
}

.swatch-dot {
  width: 18px;
  height: 18px;
  border-radius: 50%;
  flex-shrink: 0;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.25);
}

.swatch-name {
  flex: 1;
  text-align: left;
}

.swatch-check {
  opacity: 0;
  color: var(--accent-text);
  font-weight: 800;
}

.accent-swatch-btn.active .swatch-check {
  opacity: 1;
}

/* TOPIC FILTER BAR */
.topic-bar-wrapper {
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border-subtle);
  padding: 0.6rem 1.5rem;
}

.topic-filter-bar {
  max-width: 1440px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
}

.topic-pill {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
  padding: 0.36rem 0.72rem;
  border-radius: 999px;
  font-size: 0.79rem;
  font-weight: 500;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.42rem;
  transition: all 0.15s ease;
}

.topic-pill:hover {
  border-color: var(--accent-hover);
  color: var(--text-primary);
}

.topic-pill.active {
  background: var(--accent-soft-bg);
  border-color: var(--accent-primary);
  color: var(--accent-text);
  font-weight: 600;
}

.topic-count {
  background: var(--bg-elevated);
  padding: 0.08rem 0.42rem;
  border-radius: 999px;
  font-size: 0.69rem;
  font-family: var(--font-mono);
}

/* MAIN WORKSPACE LAYOUT */
.main-layout {
  max-width: 1440px;
  width: 100%;
  margin: 0 auto;
  padding: 1.35rem 1.5rem;
  display: grid;
  grid-template-columns: minmax(0, 1fr) 375px;
  gap: 1.4rem;
  align-items: start;
}

/* Grid children must be allowed to shrink below form-control min-content size. */
.main-layout > * {
  min-width: 0;
}

@media (max-width: 1080px) {
  .main-layout {
    grid-template-columns: minmax(0, 1fr);
  }
}

/* QUESTION CARD */
.question-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.45rem;
  box-shadow: var(--shadow-card);
}

.question-card-header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  padding-bottom: 0.95rem;
  border-bottom: 1px solid var(--border-subtle);
}

.q-meta-left,
.q-meta-right {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.45rem;
}

.q-number-badge {
  background: var(--accent-primary);
  color: #fff;
  font-weight: 700;
  font-size: 0.76rem;
  padding: 0.24rem 0.62rem;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
}

.q-category-badge {
  background: var(--accent-soft-bg);
  border: 1px solid var(--accent-primary);
  color: var(--accent-text);
  font-size: 0.75rem;
  font-weight: 600;
  padding: 0.2rem 0.58rem;
  border-radius: var(--radius-sm);
}

.q-subcat-badge {
  background: var(--bg-elevated);
  color: var(--text-secondary);
  font-size: 0.74rem;
  padding: 0.2rem 0.58rem;
  border-radius: var(--radius-sm);
}

.q-diff-badge {
  border: 1px solid var(--border-subtle);
  color: var(--text-muted);
  font-size: 0.71rem;
  padding: 0.18rem 0.52rem;
  border-radius: var(--radius-sm);
}

.prev-status-pill {
  font-size: 0.73rem;
  font-weight: 600;
  padding: 0.2rem 0.52rem;
  border-radius: var(--radius-sm);
}

.prev-correct {
  background: var(--success-bg);
  color: var(--success);
}

.prev-wrong {
  background: var(--danger-bg);
  color: var(--danger);
}

.flag-btn {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
  font-size: 0.76rem;
  font-weight: 600;
  padding: 0.26rem 0.62rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
}

.flag-btn.flagged {
  background: var(--warning-bg);
  border-color: var(--warning);
  color: var(--warning);
}

/* ============================================================================
   LEARN MODE: SEQUENCE CONCEPT PRIMER BANNER
   ============================================================================ */
.concept-primer-banner {
  margin-top: 1rem;
  background: var(--accent-soft-bg);
  border: 1px solid var(--accent-primary);
  border-left: 4px solid var(--accent-primary);
  border-radius: var(--radius-md);
  padding: 0.9rem 1.1rem;
}

.primer-top-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 0.4rem;
}

.primer-badge-title {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--accent-text);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.btn-toggle-primer {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
  font-size: 0.72rem;
  font-weight: 600;
  padding: 0.2rem 0.55rem;
  border-radius: 5px;
  cursor: pointer;
}

.btn-toggle-primer:hover {
  border-color: var(--accent-hover);
  color: var(--text-primary);
}

.primer-blurb-text {
  font-size: 0.88rem;
  color: var(--text-primary);
  margin-bottom: 0.6rem;
  line-height: 1.55;
}

.primer-formula-pill {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  background: var(--bg-console);
  border: 1px solid var(--accent-primary);
  color: var(--accent-text);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  font-weight: 700;
  padding: 0.32rem 0.75rem;
  border-radius: 999px;
}

.question-stem {
  margin: 1.15rem 0;
  font-size: 1.04rem;
  line-height: 1.65;
  color: var(--text-primary);
}

/* ============================================================================
   MRI PROTOCOL CONSOLE PARAMETERS & DRAGGABLE TILES
   ============================================================================ */
.parameter-console {
  background: var(--bg-console);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 0.95rem 1.1rem;
  margin-bottom: 1.25rem;
}

.console-header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  font-size: 0.74rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
  font-weight: 700;
}

.console-drag-hint {
  font-size: 0.73rem;
  text-transform: none;
  letter-spacing: 0;
  color: var(--accent-text);
  font-weight: 600;
}

.btn-calc-toggle {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  color: var(--accent-text);
  padding: 0.24rem 0.6rem;
  border-radius: var(--radius-sm);
  font-size: 0.73rem;
  font-weight: 600;
  cursor: pointer;
}

.param-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(185px, 1fr));
  gap: 0.6rem;
}

.param-chip {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 0.5rem 0.7rem;
  display: flex;
  flex-direction: column;
  gap: 0.14rem;
}

/* Interactive Draggable Console Parameter Cards for Learn Modes 1 & 2 */
.draggable-param-card {
  background: var(--bg-card);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 0.55rem 0.75rem;
  display: flex;
  flex-direction: column;
  gap: 0.18rem;
  cursor: grab;
  user-select: none;
  transition: all 0.14s ease;
  position: relative;
}

.draggable-param-card:hover:not(.card-placed) {
  border-color: var(--accent-primary);
  box-shadow: 0 4px 12px var(--accent-glow);
  transform: translateY(-1px);
}

.draggable-param-card:active:not(.card-placed) {
  cursor: grabbing;
}

.draggable-param-card.card-placed {
  opacity: 0.48;
  border-style: dashed;
  cursor: pointer;
}

.card-top-line {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.35rem;
}

.drag-grip {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

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

.param-value {
  font-size: 0.92rem;
  font-weight: 700;
  color: var(--accent-text);
  font-family: var(--font-mono);
}

.placed-pill {
  font-size: 0.65rem;
  background: var(--accent-soft-bg);
  color: var(--accent-text);
  padding: 0.06rem 0.38rem;
  border-radius: 4px;
  font-weight: 700;
}

/* ============================================================================
   LEARN MODE 2: STEP 1 FORMULA ARCHITECTURE SELECTOR
   ============================================================================ */
.blueprint-selector-panel {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1.1rem;
  margin-bottom: 1.2rem;
}

.step-heading {
  font-size: 0.92rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.75rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.step-badge {
  background: var(--accent-primary);
  color: #fff;
  font-size: 0.72rem;
  padding: 0.16rem 0.52rem;
  border-radius: 999px;
  font-family: var(--font-mono);
}

.blueprint-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.7rem;
}

@media (max-width: 720px) {
  .blueprint-grid {
    grid-template-columns: 1fr;
  }
}

.blueprint-card {
  background: var(--bg-card);
  border: 2px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 0.8rem 0.95rem;
  text-align: left;
  color: var(--text-primary);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  transition: all 0.15s ease;
}

.blueprint-card:hover:not(:disabled) {
  border-color: var(--accent-hover);
}

.blueprint-card.bp-correct {
  border-color: var(--success);
  background: var(--success-bg);
}

.blueprint-card.bp-wrong {
  border-color: var(--danger);
  background: var(--danger-bg);
}

.bp-letter {
  width: 28px;
  height: 28px;
  border-radius: 6px;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 0.82rem;
  flex-shrink: 0;
}

.bp-expr {
  font-family: var(--font-mono);
  font-size: 0.84rem;
  font-weight: 600;
}

.bp-feedback-callout {
  margin-top: 0.75rem;
  padding: 0.65rem 0.85rem;
  border-radius: var(--radius-sm);
  font-size: 0.84rem;
  font-weight: 500;
}

.bp-feedback-callout.bp-fb-error {
  background: var(--danger-bg);
  border-left: 3px solid var(--danger);
  color: var(--text-primary);
}

.bp-feedback-callout.bp-fb-success {
  background: var(--success-bg);
  border-left: 3px solid var(--success);
  color: var(--text-primary);
}

/* ============================================================================
   FORMULA DROP-ZONE CHASSIS (LINEAR & FRACTION)
   ============================================================================ */
.formula-chassis-box {
  background: var(--bg-surface);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.2rem;
  margin-bottom: 1.25rem;
}

.chassis-top-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem;
  margin-bottom: 1rem;
}

.chassis-equation-area {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  padding: 1rem;
  background: var(--bg-console);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
}

.linear-chassis-row,
.fraction-numerator-row,
.fraction-denominator-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 10px;
}

.fraction-chassis-stack {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  gap: 0.55rem;
  min-width: 280px;
}

.fraction-bar-divider {
  height: 3px;
  background: var(--text-secondary);
  border-radius: 999px;
  width: 100%;
}

.chassis-op-symbol {
  font-family: var(--font-mono);
  font-size: 1.2rem;
  font-weight: 800;
  color: var(--accent-text);
  padding: 0 0.15rem;
}

.chassis-equals-block {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  font-family: var(--font-mono);
  font-weight: 700;
}

.chassis-result-pill {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
  padding: 0.5rem 0.85rem;
  border-radius: var(--radius-sm);
  font-size: 0.84rem;
}

/* Individual Formula Drop Slot */
.formula-slot {
  min-width: 165px;
  min-height: 68px;
  background: var(--bg-card);
  border: 2px dashed var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 0.5rem 0.7rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.3rem;
  transition: all 0.15s ease;
  position: relative;
}

.formula-slot.slot-empty {
  color: var(--text-muted);
  font-size: 0.76rem;
  text-align: center;
}

.formula-slot.slot-filled {
  border-style: solid;
  border-color: var(--accent-primary);
  background: var(--accent-soft-bg);
}

.formula-slot.slot-drag-over {
  border-color: var(--accent-hover);
  background: var(--accent-soft-bg);
  transform: scale(1.03);
}

.formula-slot.slot-valid {
  border-style: solid;
  border-color: #10b981 !important;
  background: rgba(16, 185, 129, 0.14) !important;
}

.formula-slot.slot-invalid {
  border-style: solid;
  border-color: #ef4444 !important;
  background: rgba(239, 68, 68, 0.14) !important;
}

.slot-filled-header {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.4rem;
}

.slot-card-name {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--text-secondary);
}

.slot-remove-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-size: 0.76rem;
  cursor: pointer;
  padding: 0 2px;
}

.slot-remove-btn:hover {
  color: var(--danger);
}

.slot-card-val {
  font-family: var(--font-mono);
  font-size: 0.92rem;
  font-weight: 800;
  color: var(--text-primary);
}

.slot-status-badge {
  font-size: 0.72rem;
  font-weight: 800;
  padding: 0.08rem 0.38rem;
  border-radius: 4px;
  font-family: var(--font-mono);
}

.slot-badge-valid {
  background: #10b981;
  color: #052e16;
}

.slot-badge-invalid {
  background: #ef4444;
  color: #fff;
}

/* In-Slot Unit Conversion Mini-Pill Toggle */
.unit-toggle-group {
  display: inline-flex;
  background: var(--bg-console);
  border: 1px solid var(--border-subtle);
  border-radius: 999px;
  padding: 2px;
  gap: 2px;
  margin-top: 2px;
}

.unit-pill-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: 0.68rem;
  font-weight: 600;
  padding: 0.18rem 0.48rem;
  border-radius: 999px;
  cursor: pointer;
  transition: all 0.12s ease;
}

.unit-pill-btn.active {
  background: var(--accent-primary);
  color: #fff;
}

.chassis-actions-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: flex-end;
  gap: 0.65rem;
  margin-top: 0.95rem;
}

/* Slot-Level Diagnostic Callouts & Live Substitution Animation */
.slot-diagnostics-list {
  margin-top: 0.9rem;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.slot-diag-callout {
  background: var(--danger-bg);
  border: 1px solid rgba(239, 68, 68, 0.45);
  border-left: 4px solid #ef4444;
  border-radius: var(--radius-sm);
  padding: 0.65rem 0.85rem;
  font-size: 0.85rem;
  color: var(--text-primary);
}

.slot-diag-callout strong {
  color: #f87171;
}

.live-substitution-banner {
  margin-top: 0.95rem;
  background: var(--success-bg);
  border: 1.5px solid #10b981;
  border-radius: var(--radius-md);
  padding: 0.85rem 1.1rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.65rem;
  animation: popIn 0.28s cubic-bezier(0.16, 1, 0.3, 1);
}

@keyframes popIn {
  from {
    opacity: 0;
    transform: translateY(6px) scale(0.98);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

.live-sub-label {
  font-size: 0.78rem;
  font-weight: 700;
  color: #10b981;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.live-sub-math {
  font-family: var(--font-mono);
  font-size: 0.96rem;
  font-weight: 800;
  color: var(--text-primary);
}

/* SCRATCHPAD CALCULATOR */
.scratchpad-calc {
  margin-top: 0.85rem;
  padding-top: 0.85rem;
  border-top: 1px dashed var(--border-subtle);
}

.calc-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
}

.calc-input {
  flex: 1;
  min-width: 220px;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  color: var(--text-primary);
  padding: 0.45rem 0.7rem;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.85rem;
}

.calc-result {
  font-family: var(--font-mono);
  font-weight: 700;
  color: var(--success);
  font-size: 0.9rem;
  padding: 0.25rem 0.5rem;
}

/* MULTIPLE CHOICE OPTIONS */
.mc-options-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.85rem;
  margin-bottom: 1.35rem;
}

@media (max-width: 720px) {
  .mc-options-grid {
    grid-template-columns: 1fr;
  }
}

.mc-option-btn {
  background: var(--bg-surface);
  border: 2px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 0.95rem 1rem;
  color: var(--text-primary);
  text-align: left;
  display: flex;
  align-items: flex-start;
  gap: 0.85rem;
  cursor: pointer;
  transition: all 0.15s ease;
}

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

.mc-option-btn.selected {
  border-color: var(--accent-primary);
  background: var(--accent-soft-bg);
}

.mc-option-btn.opt-correct {
  border-color: var(--success);
  background: var(--success-bg);
}

.mc-option-btn.opt-incorrect-selected {
  border-color: var(--danger);
  background: var(--danger-bg);
}

.mc-option-btn.opt-dimmed {
  opacity: 0.78;
}

.mc-option-letter {
  width: 30px;
  height: 30px;
  border-radius: 7px;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  flex-shrink: 0;
}

.mc-option-btn.selected .mc-option-letter {
  background: var(--accent-primary);
  color: #fff;
  border-color: var(--accent-primary);
}

.mc-option-body {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.mc-option-text {
  font-size: 0.95rem;
  font-weight: 600;
}

.opt-tag {
  display: inline-block;
  font-size: 0.7rem;
  font-family: var(--font-mono);
  padding: 0.12rem 0.45rem;
  border-radius: 4px;
  width: fit-content;
}

.tag-correct {
  background: rgba(16, 185, 129, 0.22);
  color: var(--success);
}

.tag-trap {
  background: rgba(239, 68, 68, 0.22);
  color: var(--danger);
}

.tag-neutral {
  background: rgba(148, 163, 184, 0.15);
  color: var(--text-muted);
}

/* NUMERIC FREE-RESPONSE */
.numeric-response-panel {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1.15rem;
  margin-bottom: 1.35rem;
}

.numeric-label {
  display: block;
  font-size: 0.9rem;
  margin-bottom: 0.6rem;
  color: var(--text-secondary);
}

.numeric-input-row {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  max-width: 420px;
}

.numeric-input {
  flex: 1;
  min-width: 0;
  width: 100%;
  background: var(--bg-console);
  border: 2px solid var(--border-subtle);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 1.05rem;
  padding: 0.65rem 0.9rem;
  border-radius: var(--radius-md);
}

.numeric-input:focus {
  outline: none;
  border-color: var(--accent-primary);
}

.numeric-unit-badge {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  color: var(--accent-text);
  font-family: var(--font-mono);
  font-weight: 700;
  padding: 0.6rem 0.85rem;
  border-radius: var(--radius-md);
  font-size: 0.9rem;
}

.numeric-hint {
  margin-top: 0.55rem;
  font-size: 0.76rem;
  color: var(--text-muted);
}

/* ACTION BAR */
.action-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  padding-top: 0.4rem;
}

.action-left,
.action-right {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.6rem;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-hover));
  border: none;
  color: #fff;
  font-weight: 700;
  font-size: 0.86rem;
  padding: 0.64rem 1.2rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  box-shadow: 0 4px 12px var(--accent-glow);
  transition: all 0.15s ease;
}

.btn-primary:hover {
  transform: translateY(-1px);
  filter: brightness(1.06);
}

.btn-secondary {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  color: var(--text-primary);
  font-weight: 600;
  font-size: 0.84rem;
  padding: 0.6rem 0.95rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all 0.15s ease;
}

.btn-secondary:hover {
  border-color: var(--accent-hover);
}

/* POST-SUBMISSION DIAGNOSTIC FEEDBACK PANEL */
.feedback-panel {
  margin-top: 1.4rem;
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--border-subtle);
  background: var(--bg-surface);
}

.feedback-correct {
  border-color: rgba(16, 185, 129, 0.5);
}

.feedback-incorrect {
  border-color: rgba(239, 68, 68, 0.5);
}

.feedback-banner {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1rem 1.25rem;
}

.feedback-correct .feedback-banner {
  background: var(--success-bg);
  border-bottom: 1px solid rgba(16, 185, 129, 0.3);
}

.feedback-incorrect .feedback-banner {
  background: var(--danger-bg);
  border-bottom: 1px solid rgba(239, 68, 68, 0.3);
}

.banner-icon {
  width: 38px;
  height: 38px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  font-weight: 800;
  flex-shrink: 0;
}

.feedback-correct .banner-icon {
  background: var(--success);
  color: #052e16;
}

.feedback-incorrect .banner-icon {
  background: var(--danger);
  color: #fff;
}

.banner-content h3 {
  font-size: 1rem;
  margin-bottom: 0.2rem;
}

.banner-sub {
  font-size: 0.82rem;
  color: var(--text-secondary);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
}

.error-code-pill {
  background: rgba(239, 68, 68, 0.22);
  color: var(--danger);
  font-family: var(--font-mono);
  font-size: 0.74rem;
  padding: 0.1rem 0.5rem;
  border-radius: 4px;
}

.feedback-sections-grid {
  padding: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 1.1rem;
}

.feedback-box {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1.05rem 1.2rem;
}

.box-title-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.6rem;
  margin-bottom: 0.65rem;
}

.box-step-num {
  width: 24px;
  height: 24px;
  border-radius: 6px;
  background: var(--accent-soft-bg);
  border: 1px solid var(--accent-primary);
  color: var(--accent-text);
  font-weight: 700;
  font-size: 0.78rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
}

.box-title-row h4 {
  font-size: 0.94rem;
  color: var(--text-primary);
}

.citation-badge {
  margin-left: auto;
  background: var(--accent-soft-bg);
  border: 1px solid var(--accent-primary);
  color: var(--accent-text);
  font-size: 0.74rem;
  font-weight: 600;
  padding: 0.18rem 0.55rem;
  border-radius: 999px;
}

.diagnosis-main-text {
  font-size: 0.92rem;
  color: var(--text-primary);
  margin-bottom: 0.65rem;
}

.trap-calc-box {
  background: var(--bg-console);
  border-left: 3px solid var(--warning);
  padding: 0.45rem 0.75rem;
  font-size: 0.82rem;
  margin-bottom: 0.75rem;
  border-radius: 4px;
}

.trap-calc-box code {
  font-family: var(--font-mono);
  color: var(--warning);
}

.all-traps-details {
  margin-top: 0.6rem;
  border-top: 1px solid var(--border-subtle);
  padding-top: 0.6rem;
}

.all-traps-details summary {
  cursor: pointer;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent-text);
  user-select: none;
}

.traps-list {
  margin-top: 0.65rem;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.trap-breakdown-item {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 0.65rem 0.8rem;
}

.trap-breakdown-item.highlighted-trap {
  border-color: var(--danger);
  background: var(--danger-bg);
}

.trap-item-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  margin-bottom: 0.25rem;
}

.trap-letter-pill {
  font-weight: 700;
  font-size: 0.82rem;
  color: var(--text-primary);
}

.trap-code-badge {
  background: var(--warning-bg);
  color: var(--warning);
  font-family: var(--font-mono);
  font-size: 0.7rem;
  padding: 0.1rem 0.45rem;
  border-radius: 4px;
}

.trap-item-desc {
  font-size: 0.82rem;
  color: var(--text-secondary);
}

.math-steps-list {
  padding-left: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
}

.math-steps-list li {
  font-size: 0.89rem;
  color: var(--text-primary);
  font-family: var(--font-mono);
  background: var(--bg-console);
  padding: 0.45rem 0.75rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-subtle);
}

.grounded-explanation {
  font-size: 0.92rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.tradeoff-matrix-cards {
  margin-top: 0.95rem;
  padding-top: 0.85rem;
  border-top: 1px solid var(--border-subtle);
}

.tradeoff-matrix-cards h4 {
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--text-muted);
  margin-bottom: 0.65rem;
}

.tradeoff-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 0.65rem;
}

.tradeoff-mini-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 0.7rem;
}

.tm-header {
  font-weight: 700;
  font-size: 0.84rem;
  color: var(--accent-text);
  margin-bottom: 0.45rem;
}

.tm-cols {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.5rem;
  font-size: 0.76rem;
}

.tm-col ul {
  padding-left: 1rem;
  margin-top: 0.2rem;
  color: var(--text-secondary);
}

.tm-benefits strong {
  color: var(--success);
}

.tm-limits strong {
  color: var(--danger);
}

/* SIDEBAR: PROGRESS TRACKER & DECK NAVIGATOR */
.sidebar-column {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.sidebar-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.15rem;
  box-shadow: var(--shadow-card);
}

.sidebar-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0.85rem;
}

.sidebar-card-header h3 {
  font-size: 0.95rem;
  font-weight: 700;
}

.btn-link-danger {
  background: transparent;
  border: 1px solid rgba(239, 68, 68, 0.4);
  color: var(--danger);
  font-size: 0.72rem;
  padding: 0.18rem 0.5rem;
  border-radius: 4px;
  cursor: pointer;
}

.kpi-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.kpi-box {
  background: var(--bg-console);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 0.55rem 0.4rem;
  text-align: center;
  display: flex;
  flex-direction: column;
}

.kpi-val {
  font-size: 1.05rem;
  font-weight: 800;
  color: var(--accent-text);
  font-family: var(--font-mono);
}

.kpi-lbl {
  font-size: 0.68rem;
  color: var(--text-muted);
}

.category-breakdown-list {
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.cat-progress-item {
  display: flex;
  flex-direction: column;
  gap: 0.22rem;
}

.cat-prog-top {
  display: flex;
  justify-content: space-between;
  font-size: 0.75rem;
}

.cat-prog-name {
  color: var(--text-secondary);
  font-weight: 500;
}

.cat-prog-stat {
  font-family: var(--font-mono);
  color: var(--text-muted);
}

.cat-prog-bar-bg {
  height: 6px;
  background: var(--bg-console);
  border-radius: 999px;
  overflow: hidden;
}

.cat-prog-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent-primary), var(--accent-hover));
  border-radius: 999px;
  transition: width 0.3s ease;
}

/* DECK NAVIGATOR GRID */
.status-filter-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  margin-bottom: 0.75rem;
}

.status-chip {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
  font-size: 0.72rem;
  padding: 0.24rem 0.55rem;
  border-radius: 6px;
  cursor: pointer;
}

.status-chip.active {
  background: var(--accent-soft-bg);
  border-color: var(--accent-primary);
  color: var(--accent-text);
  font-weight: 600;
}

.deck-grid {
  display: grid;
  grid-template-columns: repeat(10, 1fr);
  gap: 4px;
  margin-bottom: 0.75rem;
}

.deck-num-btn {
  aspect-ratio: 1;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 5px;
  color: var(--text-secondary);
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
}

.deck-num-btn:hover {
  border-color: var(--accent-hover);
  color: var(--text-primary);
}

.deck-num-btn.current {
  outline: 2px solid var(--accent-primary);
  outline-offset: 1px;
  font-weight: 800;
  color: var(--accent-text);
}

.deck-num-btn.answered-correct {
  background: var(--success-bg);
  border-color: var(--success);
  color: var(--success);
}

.deck-num-btn.answered-wrong {
  background: var(--danger-bg);
  border-color: var(--danger);
  color: var(--danger);
}

.deck-num-btn.is-flagged::after {
  content: '';
  position: absolute;
  top: 2px;
  right: 2px;
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--warning);
}

.deck-num-btn.filtered-out {
  opacity: 0.22;
}

.deck-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  font-size: 0.72rem;
  color: var(--text-muted);
}

.deck-legend .dot {
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 2px;
  margin-right: 4px;
}

.dot-correct {
  background: var(--success);
}
.dot-wrong {
  background: var(--danger);
}
.dot-flagged {
  background: var(--warning);
}
.dot-unanswered {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
}

/* REFERENCE DRAWER */
.drawer-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(4, 9, 20, 0.72);
  backdrop-filter: blur(3px);
  z-index: 90;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease;
}

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

.reference-drawer {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  width: min(760px, 94vw);
  background: var(--bg-surface);
  border-left: 1px solid var(--border-subtle);
  z-index: 100;
  transform: translateX(100%);
  transition: transform 0.25s cubic-bezier(0.16, 1, 0.3, 1);
  display: flex;
  flex-direction: column;
  box-shadow: -12px 0 40px rgba(0, 0, 0, 0.6);
}

.reference-drawer.open {
  transform: translateX(0);
}

.drawer-header {
  padding: 1.1rem 1.4rem;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.drawer-header h2 {
  font-size: 1.05rem;
}

.drawer-subtitle {
  font-size: 0.76rem;
  color: var(--text-muted);
  margin-top: 2px;
}

.drawer-pdf-link {
  color: var(--accent-text);
  font-weight: 600;
}

.drawer-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  padding: 0.75rem 1.4rem;
  background: var(--bg-console);
  border-bottom: 1px solid var(--border-subtle);
}

.drawer-tab-btn {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
  padding: 0.45rem 0.9rem;
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
}

.drawer-tab-btn.active {
  background: var(--accent-primary);
  border-color: var(--accent-primary);
  color: #fff;
}

.drawer-body {
  padding: 1.25rem 1.4rem;
  overflow-y: auto;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.ref-constants-box {
  background: var(--bg-console);
  border: 1px solid var(--accent-primary);
  border-radius: var(--radius-md);
  padding: 0.9rem 1.1rem;
}

.ref-constants-box h4 {
  font-size: 0.85rem;
  color: var(--accent-text);
  margin-bottom: 0.5rem;
}

.constants-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  font-size: 0.78rem;
}

.constants-pills span {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  padding: 0.25rem 0.6rem;
  border-radius: 6px;
}

.ref-formula-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1rem 1.15rem;
}

.ref-card-top {
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 0.4rem;
}

.ref-cat-tag {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--accent-text);
  text-transform: uppercase;
}

.ref-cite-tag {
  font-size: 0.72rem;
  color: var(--text-muted);
}

.ref-formula-card h4 {
  font-size: 0.95rem;
  margin-bottom: 0.55rem;
}

.ref-expr-list {
  padding-left: 1.15rem;
  margin-bottom: 0.6rem;
  font-size: 0.82rem;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.ref-expr-list code {
  font-family: var(--font-mono);
  color: var(--success);
  background: var(--bg-console);
  padding: 0.1rem 0.4rem;
  border-radius: 4px;
}

.ref-concept-note {
  font-size: 0.82rem;
  color: var(--text-secondary);
}

.tradeoff-ref-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.8rem;
}

.tradeoff-ref-table th,
.tradeoff-ref-table td {
  border: 1px solid var(--border-subtle);
  padding: 0.65rem 0.75rem;
  vertical-align: top;
  text-align: left;
}

.tradeoff-ref-table th {
  background: var(--bg-console);
  color: var(--accent-text);
}

.compact-list {
  padding-left: 1rem;
}

.table-cite {
  font-size: 0.68rem;
  color: var(--text-muted);
  margin-top: 0.25rem;
}

.sidebar-note {
  font-size: 0.82rem;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
}

.empty-filter-state {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 2.5rem;
  text-align: center;
}

.empty-filter-state p {
  margin: 0.65rem 0 1.25rem;
  color: var(--text-secondary);
}

/* ============================================================================
   CONSOLIDATED SINGLE-ROW 3-DROPDOWN CONTROL BAR & ⓘ INFO POPOVERS
   ============================================================================ */
.dropdown-control-bar-wrapper {
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border-subtle);
  padding: 0.75rem 1.5rem;
  position: relative;
  z-index: 40;
}

.dropdown-control-bar {
  max-width: 1440px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1.1rem;
  align-items: end;
}

@media (max-width: 1080px) {
  .dropdown-control-bar {
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 0.85rem;
  }
}

.control-dropdown-group {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  min-width: 0;
}

.control-label-row {
  display: flex;
  align-items: center;
  gap: 0.42rem;
}

.control-dropdown-label {
  font-size: 0.74rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
}

.control-select {
  width: 100%;
  background-color: var(--bg-card);
  color: var(--text-primary);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 0.52rem 2.1rem 0.52rem 0.8rem;
  font-size: 16px;
  font-weight: 600;
  font-family: var(--font-sans);
  cursor: pointer;
  appearance: none;
  background-image: linear-gradient(45deg, transparent 50%, var(--accent-text) 50%),
    linear-gradient(135deg, var(--accent-text) 50%, transparent 50%);
  background-position: calc(100% - 16px) calc(50% - 2px), calc(100% - 11px) calc(50% - 2px);
  background-size: 5px 5px, 5px 5px;
  background-repeat: no-repeat;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.control-select:hover {
  border-color: var(--accent-hover);
}

.control-select:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px var(--accent-soft-bg);
}

/* ⓘ Info Button & Floating Popover */
.info-popover-wrapper {
  position: relative;
  display: inline-flex;
  align-items: center;
}

.info-icon-btn {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  border: 1px solid var(--border-subtle);
  background: var(--bg-elevated);
  color: var(--accent-text);
  font-size: 0.74rem;
  font-weight: 700;
  line-height: 1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.15s ease;
}

.info-icon-btn:hover,
.info-icon-btn.active {
  background: var(--accent-primary);
  border-color: var(--accent-primary);
  color: #fff;
  box-shadow: 0 2px 8px var(--accent-glow);
}

.info-popover-card {
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  width: min(310px, 88vw);
  background: var(--bg-card);
  border: 1px solid var(--accent-primary);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-popover);
  padding: 0.8rem 0.95rem;
  font-size: 0.79rem;
  color: var(--text-secondary);
  line-height: 1.5;
  z-index: 130;
  display: none;
}

.info-popover-card.info-popover-wide {
  width: min(360px, 90vw);
}

.info-popover-card.info-popover-right {
  left: auto;
  right: 0;
}

.info-popover-card.open {
  display: block;
}

.info-popover-list {
  padding-left: 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.info-popover-list strong {
  color: var(--text-primary);
}

/* ============================================================================
   "❓ HOW TO USE THIS MODULE" QUICK-START MODAL
   ============================================================================ */
.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(4, 9, 20, 0.76);
  backdrop-filter: blur(4px);
  z-index: 150;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 1.25rem;
}

.modal-backdrop.open {
  display: flex;
}

.how-to-modal {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  width: min(880px, 96vw);
  max-height: 90vh;
  overflow-y: auto;
  box-shadow: var(--shadow-popover);
  display: flex;
  flex-direction: column;
}

.how-to-modal-header {
  padding: 1.15rem 1.45rem;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.modal-eyebrow {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent-text);
  display: block;
  margin-bottom: 2px;
}

.how-to-modal-header h2 {
  font-size: 1.15rem;
  color: var(--text-primary);
}

.how-to-cards-grid {
  padding: 1.35rem 1.45rem;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

@media (max-width: 720px) {
  .how-to-cards-grid {
    grid-template-columns: 1fr;
  }
}

.how-to-card {
  background: var(--bg-console);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1.05rem 1.15rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.how-to-step-badge {
  align-self: flex-start;
  background: var(--accent-soft-bg);
  border: 1px solid var(--accent-primary);
  color: var(--accent-text);
  font-size: 0.71rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.16rem 0.55rem;
  border-radius: 999px;
}

.how-to-card h3 {
  font-size: 0.95rem;
  color: var(--text-primary);
}

.how-to-card ul {
  padding-left: 1.1rem;
  font-size: 0.82rem;
  color: var(--text-secondary);
  display: flex;
  flex-direction: column;
  gap: 0.42rem;
}

.how-to-card code {
  font-family: var(--font-mono);
  color: var(--accent-text);
  background: var(--bg-card);
  padding: 0.08rem 0.35rem;
  border-radius: 4px;
  font-size: 0.78rem;
}

.how-to-modal-footer {
  padding: 0.95rem 1.45rem;
  background: var(--bg-surface);
  border-top: 1px solid var(--border-subtle);
  display: flex;
  justify-content: flex-end;
}

/* ============================================================================
   TABLET & MOBILE TOUCH OPTIMIZATIONS (iPadOS / iOS Safari / Android)
   ============================================================================ */
.console-card,
.draggable-param-card,
.formula-slot,
.blueprint-card,
button {
  user-select: none;
  -webkit-user-select: none;
  -webkit-touch-callout: none;
  touch-action: manipulation;
}

/* Prevent iOS/iPadOS Safari Input Auto-Zoom on Focus */
select,
input[type="text"],
input[type="number"],
.control-select,
.numeric-input,
.calc-input {
  font-size: 16px;
}

/* Tap-to-Select / Tap-to-Slot Highlight Ring */
.console-card.card-selected,
.draggable-param-card.card-selected {
  border-color: var(--accent-primary) !important;
  border-style: solid !important;
  opacity: 1 !important;
  box-shadow: 0 0 0 3px var(--accent-glow), 0 6px 16px rgba(0, 0, 0, 0.3);
  transform: translateY(-2px);
}

.selected-pill {
  font-size: 0.64rem;
  background: var(--accent-primary);
  color: #fff;
  padding: 0.08rem 0.42rem;
  border-radius: 4px;
  font-weight: 700;
}

.formula-slot.slot-awaiting-selection {
  border-color: var(--accent-hover);
  box-shadow: 0 0 0 2px var(--accent-soft-bg);
}

/* Desktop vs Touch Helper Text */
.hint-touch {
  display: none;
}

@media (pointer: coarse) {
  .hint-desktop {
    display: none;
  }
  .hint-touch {
    display: inline;
  }

  /* Minimum 44px × 44px Touch Targets on Tablets & Mobile */
  .info-icon-btn {
    min-width: 44px;
    min-height: 44px;
    width: 44px;
    height: 44px;
    font-size: 0.92rem;
  }

  .unit-pill-btn {
    min-height: 44px;
    min-width: 44px;
    padding: 0.4rem 0.75rem;
    font-size: 0.78rem;
    display: inline-flex;
    align-items: center;
    justify-content: center;
  }

  .deck-num-btn {
    min-width: 44px;
    min-height: 44px;
    font-size: 0.78rem;
  }

  .deck-grid {
    grid-template-columns: repeat(auto-fill, minmax(44px, 1fr));
    gap: 6px;
  }

  .slot-remove-btn,
  #close-how-to-use-btn,
  #close-reference-drawer {
    min-width: 44px;
    min-height: 44px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
  }
}