* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-width: 320px;
  min-height: 100%;
  background: var(--surface-canvas);
  color: var(--text-primary);
  font-family: var(--font-ui);
}

html,
body {
  overflow: hidden;
}

/* Respect the HTML hidden state even when a component has its own display rule. */
.app-shell [hidden] {
  display: none !important;
}

button,
a {
  font: inherit;
}

button {
  color: inherit;
}

.app-shell {
  height: 100dvh;
  min-height: 0;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr);
  background: var(--surface-canvas);
}

.app-shell__topbar {
  min-height: 64px;
  display: grid;
  grid-template-areas: "brand context status";
  grid-template-columns: minmax(180px, 0.8fr) minmax(320px, 2fr) minmax(160px, 0.8fr);
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-3) var(--space-5);
  border-bottom: 1px solid var(--divider-default);
  background: var(--surface-base);
  z-index: 3;
}

.brand {
  grid-area: brand;
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  width: max-content;
  color: var(--text-primary);
  text-decoration: none;
  font-weight: var(--weight-bold);
  letter-spacing: -0.02em;
}

.brand__mark {
  width: 36px;
  height: 36px;
  display: grid;
  place-items: center;
  border-radius: var(--radius-md);
  background: var(--mode-accent);
  color: var(--mode-accent-text);
  font-family: var(--font-math);
  font-size: var(--text-xl);
  line-height: 1;
}

.brand__text {
  font-size: var(--text-md);
}

.topic-navigation-toggle {
  grid-area: nav-toggle;
  display: none;
  min-height: var(--touch-target-min);
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-base);
  color: var(--text-secondary);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.topic-navigation-toggle__icon {
  width: 18px;
  display: grid;
  gap: 3px;
}

.topic-navigation-toggle__icon span {
  height: 2px;
  border-radius: var(--radius-pill);
  background: currentColor;
}

.topbar__context,
.topbar__status {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-width: 0;
}

.topbar__context {
  grid-area: context;
  justify-content: center;
}

.breadcrumb {
  color: var(--text-secondary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.scope-badge {
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  min-height: 30px;
  padding: 0 var(--space-3);
  border: 1px solid var(--scope-border);
  border-radius: var(--radius-pill);
  background: var(--scope-background);
  color: var(--scope-text);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  letter-spacing: 0.02em;
  text-transform: uppercase;
}

.scope-badge--compact {
  min-height: 24px;
  padding: 0 var(--space-2);
  font-size: 0.64rem;
  letter-spacing: 0.025em;
}

.topbar__status {
  grid-area: status;
  justify-content: flex-end;
  color: var(--text-muted);
  font-size: var(--text-sm);
}

.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--feedback-info-accent);
}

.app-shell__body {
  position: relative;
  min-height: 0;
  display: grid;
  grid-template-columns: 248px minmax(0, 1fr);
  gap: var(--space-4);
  padding: var(--space-4);
  overflow: hidden;
}

.navigation-scrim {
  display: none;
}

.topic-navigation {
  min-height: 0;
  overflow: auto;
  padding: var(--space-4);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-base);
  box-shadow: var(--shadow-raised);
}

.topic-navigation__heading-row {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-3);
}

.topic-navigation__heading {
  display: grid;
  gap: var(--space-1);
  margin-bottom: var(--space-4);
}

.topic-navigation__close {
  display: none;
  width: var(--touch-target-min);
  height: var(--touch-target-min);
  flex: 0 0 auto;
  place-items: center;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-base);
  color: var(--text-secondary);
  font-size: var(--text-xl);
  line-height: 1;
  cursor: pointer;
}

.eyebrow,
.activity-overline,
.activity-callout__label {
  margin: 0;
  color: var(--text-muted);
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.topic-navigation__course {
  color: var(--text-secondary);
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
}

.topic-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  gap: var(--space-2);
}

.topic-link {
  width: 100%;
  min-height: var(--touch-target-min);
  display: grid;
  grid-template-columns: 26px minmax(0, 1fr) 22px;
  gap: var(--space-2);
  align-items: start;
  padding: var(--space-2) var(--space-2);
  border: 1px solid transparent;
  border-radius: var(--radius-md);
  background: transparent;
  text-align: left;
  cursor: pointer;
}

.topic-link__body {
  min-width: 0;
  display: grid;
  gap: 5px;
}

.topic-link__title {
  min-width: 0;
  line-height: var(--leading-tight);
}

.topic-mode-progress {
  display: flex;
  flex-wrap: wrap;
  gap: 2px;
  min-height: 18px;
}

.mode-progress-marker {
  min-width: 22px;
  height: 18px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 2px;
  padding: 0 2px;
  border: 1px solid var(--progress-not-started);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-muted);
  font-size: 0.58rem;
  font-weight: var(--weight-bold);
  line-height: 1;
}

.mode-progress-marker[data-progress-state="partial"] {
  border-color: var(--progress-in-progress);
  box-shadow: inset 0 -3px 0 var(--progress-in-progress);
  color: var(--text-primary);
}

.mode-progress-marker[data-progress-state="complete"] {
  border-color: var(--progress-complete);
  background: var(--progress-complete);
  color: var(--surface-base);
}

.topic-state-marker {
  width: 22px;
  height: 22px;
  display: inline-grid;
  place-items: center;
  align-self: center;
  border: 1px solid var(--progress-not-started);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-muted);
  font-size: 0.72rem;
  font-weight: var(--weight-bold);
  line-height: 1;
}

.topic-state-marker[data-progress-state="partial"] {
  border-color: var(--progress-in-progress);
  box-shadow: inset 0 -6px 0 var(--progress-in-progress);
  color: var(--text-primary);
}

.topic-state-marker[data-progress-state="complete"] {
  border-color: var(--progress-complete);
  background: var(--progress-complete);
  color: var(--surface-base);
}

.visually-hidden {
  position: absolute !important;
  width: 1px !important;
  height: 1px !important;
  padding: 0 !important;
  margin: -1px !important;
  overflow: hidden !important;
  clip: rect(0, 0, 0, 0) !important;
  white-space: nowrap !important;
  border: 0 !important;
}

.topic-link:hover {
  background: var(--surface-subtle);
}

.topic-link.is-current {
  border-color: var(--border-default);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  font-weight: var(--weight-semibold);
}

.topic-index {
  color: var(--text-muted);
  font-size: var(--text-xs);
  font-variant-numeric: tabular-nums;
}

.topic-navigation__section {
  display: grid;
  gap: var(--space-2);
}

.topic-navigation__section + .topic-navigation__section {
  margin-top: var(--space-4);
}

.topic-navigation__section-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
  padding: 0 var(--space-1);
}

.topic-navigation__section-label {
  color: var(--text-secondary);
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.topic-list--secondary .topic-link {
  color: var(--text-secondary);
}

.topic-link--review {
  border-color: var(--scope-border);
  background: var(--scope-background);
  color: var(--scope-text);
  font-weight: var(--weight-semibold);
}

.topic-link--review:hover {
  background: var(--scope-background);
}

.topic-navigation__checkpoint {
  display: grid;
  grid-template-columns: minmax(10px, 1fr) minmax(0, auto) minmax(10px, 1fr);
  gap: var(--space-2);
  align-items: center;
  margin: var(--space-4) 0;
}

.checkpoint-rule {
  height: 2px;
  border-radius: var(--radius-pill);
  background: var(--progress-complete);
}

.checkpoint-copy {
  display: grid;
  gap: 2px;
  max-width: 150px;
  color: var(--text-secondary);
  text-align: center;
}

.checkpoint-copy strong {
  color: var(--text-primary);
  font-size: 0.67rem;
  letter-spacing: 0.045em;
  line-height: var(--leading-tight);
  text-transform: uppercase;
}

.checkpoint-copy span {
  color: var(--text-muted);
  font-size: 0.63rem;
  line-height: var(--leading-tight);
}

.topic-navigation__full-course {
  display: grid;
  gap: var(--space-2);
  margin-top: var(--space-4);
  padding: var(--space-3);
  border: 1px solid var(--scope-border);
  border-radius: var(--radius-md);
  background: var(--scope-background);
  color: var(--scope-text);
}

.topic-navigation__full-course-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
}

.topic-navigation__full-course > .scope-badge,
.topic-navigation__full-course-heading > .scope-badge {
  justify-self: start;
}

.topic-mode-progress--full {
  margin-top: var(--space-2);
}

.topic-navigation__full-course > div {
  display: grid;
  gap: 2px;
}

.topic-navigation__full-course strong {
  font-size: var(--text-sm);
}

.topic-navigation__full-course div span {
  color: var(--text-secondary);
  font-size: var(--text-xs);
  line-height: var(--leading-normal);
}

.learning-workspace {
  min-width: 0;
  min-height: 0;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) auto;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-base);
  box-shadow: var(--shadow-raised);
  overflow: hidden;
}

.workspace-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-5);
  padding: var(--space-4) var(--space-5);
  border-bottom: 1px solid var(--divider-default);
}

.workspace-header h1 {
  margin: var(--space-1) 0 0;
  font-size: var(--text-xl);
  line-height: var(--leading-tight);
  letter-spacing: -0.025em;
}

.mode-tabs {
  width: min(100%, 570px);
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: var(--space-1);
  padding: var(--space-1);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-subtle);
}

.mode-tab {
  min-width: 0;
  min-height: var(--touch-target-min);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-2);
  border: 1px solid transparent;
  border-radius: var(--radius-md);
  background: transparent;
  color: var(--text-secondary);
  cursor: pointer;
  transition:
    background-color var(--motion-fast) var(--motion-easing),
    border-color var(--motion-fast) var(--motion-easing),
    color var(--motion-fast) var(--motion-easing),
    box-shadow var(--motion-fast) var(--motion-easing);
}

.mode-tab:hover {
  background: var(--mode-soft);
  color: var(--mode-soft-text);
}

.mode-tab[aria-selected="true"] {
  border-color: var(--mode-accent);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  box-shadow: inset 0 -3px 0 var(--mode-accent);
}

.mode-tab__icon {
  width: 20px;
  height: 20px;
  flex: 0 0 auto;
  display: grid;
  place-items: center;
  color: var(--mode-accent);
}

.mode-tab__icon svg {
  width: 100%;
  height: 100%;
  fill: none;
  stroke: currentColor;
  stroke-width: 1.8;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.mode-tab__text {
  min-width: 0;
  display: grid;
  gap: 1px;
  line-height: 1.05;
  text-align: left;
}

.mode-tab__label {
  color: currentColor;
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
  white-space: nowrap;
}

.mode-tab__sublabel {
  color: var(--text-muted);
  font-size: 0.64rem;
  font-weight: var(--weight-medium);
  white-space: nowrap;
}

.mode-tab[aria-selected="true"] .mode-tab__sublabel {
  color: var(--mode-soft-text);
}


.activity-stage__tools {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.activity-help-button {
  min-height: var(--touch-target-min);
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.activity-help-button:hover {
  border-color: var(--mode-accent);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
}

.activity-help-button__icon {
  width: 20px;
  height: 20px;
  display: inline-grid;
  place-items: center;
  border-radius: var(--radius-pill);
  background: var(--surface-subtle);
  color: var(--text-primary);
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
}

.help-drawer-scrim {
  position: absolute;
  inset: 0;
  z-index: 40;
  width: 100%;
  height: 100%;
  border: 0;
  background: var(--overlay-scrim);
  opacity: 0.72;
  cursor: pointer;
}

.help-drawer-scrim:not([hidden]) {
  display: block;
}

.help-drawer {
  position: absolute;
  inset: 0 0 0 auto;
  z-index: 50;
  width: min(388px, calc(100% - 56px));
  min-width: 0;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr);
  border-left: 1px solid var(--border-default);
  border-radius: var(--radius-lg) 0 0 var(--radius-lg);
  background: var(--surface-base);
  box-shadow: var(--shadow-drawer);
  transform: translateX(calc(100% + var(--space-4)));
  visibility: hidden;
  transition:
    transform var(--motion-normal) var(--motion-easing),
    visibility 0s linear var(--motion-normal);
}

.app-shell[data-help-open="true"] .help-drawer {
  transform: translateX(0);
  visibility: visible;
  transition-delay: 0s;
}

.help-drawer__header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-4);
  padding: var(--space-4) var(--space-5);
  border-bottom: 1px solid var(--divider-default);
}

.help-drawer__header .eyebrow {
  margin: 0;
}

.help-drawer__header h2 {
  margin: var(--space-1) 0 0;
  font-size: var(--text-xl);
  letter-spacing: -0.025em;
}

.help-drawer__close {
  width: var(--touch-target-min);
  height: var(--touch-target-min);
  flex: 0 0 auto;
  display: grid;
  place-items: center;
  border: 1px solid transparent;
  border-radius: var(--radius-pill);
  background: var(--surface-subtle);
  color: var(--text-secondary);
  font-size: var(--text-xl);
  line-height: 1;
  cursor: pointer;
}

.help-drawer__close:hover {
  border-color: var(--border-default);
  background: var(--surface-base);
  color: var(--text-primary);
}

.help-drawer__body {
  min-height: 0;
  overflow: auto;
  padding: var(--space-5);
  overscroll-behavior: contain;
}

.help-drawer__context {
  margin: 0 0 var(--space-4);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
}

.help-drawer__targets {
  display: grid;
  gap: var(--space-2);
}

.help-target {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: var(--space-3);
  min-height: 76px;
  padding: var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-base);
  color: var(--text-primary);
  text-decoration: none;
}

.help-target:hover,
.help-target:focus-visible {
  border-color: var(--mode-accent);
  background: var(--mode-soft);
}

.help-target__badge {
  min-width: 76px;
  min-height: 30px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0 var(--space-2);
  border: 1px solid var(--mode-accent);
  border-radius: var(--radius-pill);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  font-size: 0.7rem;
  font-weight: var(--weight-bold);
  letter-spacing: 0.035em;
  text-transform: uppercase;
}

.help-target__content {
  min-width: 0;
  display: grid;
  gap: 2px;
}

.help-target__content strong {
  font-size: var(--text-sm);
  line-height: var(--leading-tight);
}

.help-target__description {
  color: var(--text-secondary);
  font-size: var(--text-xs);
  line-height: var(--leading-normal);
}

.help-target__arrow {
  color: var(--mode-soft-text);
  font-size: var(--text-lg);
  line-height: 1;
}

.help-drawer__return-note {
  margin: var(--space-4) 0 0;
  padding-top: var(--space-3);
  border-top: 1px solid var(--divider-default);
  color: var(--text-muted);
  font-size: var(--text-xs);
  line-height: var(--leading-normal);
}


.word-bank-button {
  min-height: var(--touch-target-min);
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.word-bank-button:hover {
  border-color: var(--feedback-info-accent);
  background: var(--feedback-info-soft);
  color: var(--feedback-info-ink);
}

.word-bank-button__icon {
  color: var(--feedback-info-ink);
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
}

.word-bank-button__count {
  min-width: 22px;
  height: 22px;
  display: inline-grid;
  place-items: center;
  padding: 0 5px;
  border-radius: var(--radius-pill);
  background: var(--feedback-info-soft);
  color: var(--feedback-info-ink);
  font-size: 0.68rem;
  font-weight: var(--weight-bold);
  font-variant-numeric: tabular-nums;
}

.vocabulary-term-wrap {
  position: relative;
  display: inline;
}

.vocabulary-term {
  display: inline-flex;
  align-items: baseline;
  gap: 4px;
  margin: 0 1px;
  padding: 1px 4px;
  border: 0;
  border-radius: var(--radius-sm);
  background: transparent;
  color: inherit;
  font: inherit;
  line-height: inherit;
  cursor: pointer;
}

.vocabulary-term--new {
  padding-left: 1px;
  padding-right: 1px;
  border-bottom: 1px dotted var(--feedback-info-accent);
  border-radius: 0;
  color: var(--text-primary);
  font-weight: var(--weight-semibold);
}

.vocabulary-term--known {
  border-radius: var(--radius-pill);
  background: var(--feedback-info-soft);
  color: var(--feedback-info-ink);
}

.vocabulary-new-marker {
  display: inline-flex;
  align-items: center;
  min-height: 16px;
  padding: 0 4px;
  border-radius: var(--radius-pill);
  background: var(--feedback-info-soft);
  color: var(--feedback-info-ink);
  font-size: 0.56rem;
  font-weight: var(--weight-bold);
  letter-spacing: 0.06em;
}

.vocabulary-popover {
  position: absolute;
  left: 0;
  top: calc(100% + var(--space-2));
  z-index: 60;
  width: min(320px, calc(100vw - 40px));
  display: grid;
  gap: var(--space-2);
  padding: var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-raised);
  box-shadow: var(--shadow-raised);
  color: var(--text-primary);
  font-family: var(--font-ui);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
  visibility: hidden;
  opacity: 0;
  pointer-events: none;
  transform: translateY(4px);
  transition:
    opacity var(--motion-fast) var(--motion-easing),
    transform var(--motion-fast) var(--motion-easing),
    visibility 0s linear var(--motion-fast);
}

.vocabulary-term-wrap[data-popover-open="true"] .vocabulary-popover {
  visibility: visible;
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
  transition-delay: 0s;
}

@media (hover: hover) and (pointer: fine) {
  .vocabulary-term-wrap:hover .vocabulary-popover {
    visibility: visible;
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
    transition-delay: 0s;
  }
}

.vocabulary-popover__term {
  font-size: var(--text-sm);
}

.vocabulary-popover__definition {
  color: var(--text-secondary);
}

.vocabulary-popover__open-bank {
  justify-self: start;
  min-height: var(--touch-target-min);
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-base);
  color: var(--feedback-info-ink);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.app-shell[data-help-open="true"] .vocabulary-popover,
.app-shell[data-word-bank-open="true"] .vocabulary-popover {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.word-bank-drawer-scrim {
  position: absolute;
  inset: 0;
  z-index: 40;
  width: 100%;
  height: 100%;
  border: 0;
  background: var(--overlay-scrim);
  opacity: 0.72;
  cursor: pointer;
}

.word-bank-drawer-scrim:not([hidden]) {
  display: block;
}

.word-bank-drawer {
  position: absolute;
  inset: 0 0 0 auto;
  z-index: 50;
  width: min(520px, calc(100% - 56px));
  min-width: 0;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr);
  border-left: 1px solid var(--border-default);
  border-radius: var(--radius-lg) 0 0 var(--radius-lg);
  background: var(--surface-base);
  box-shadow: var(--shadow-drawer);
  transform: translateX(calc(100% + var(--space-4)));
  visibility: hidden;
  transition:
    transform var(--motion-normal) var(--motion-easing),
    visibility 0s linear var(--motion-normal);
}

.app-shell[data-word-bank-open="true"] .word-bank-drawer {
  transform: translateX(0);
  visibility: visible;
  transition-delay: 0s;
}

.word-bank-drawer__header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-4);
  padding: var(--space-4) var(--space-5);
  border-bottom: 1px solid var(--divider-default);
}

.word-bank-drawer__header h2 {
  margin: var(--space-1) 0 0;
  font-size: var(--text-xl);
  letter-spacing: -0.025em;
}

.word-bank-drawer__close {
  width: var(--touch-target-min);
  height: var(--touch-target-min);
  flex: 0 0 auto;
  display: grid;
  place-items: center;
  border: 1px solid transparent;
  border-radius: var(--radius-pill);
  background: var(--surface-subtle);
  color: var(--text-secondary);
  font-size: var(--text-xl);
  line-height: 1;
  cursor: pointer;
}

.word-bank-drawer__close:hover {
  border-color: var(--border-default);
  background: var(--surface-base);
  color: var(--text-primary);
}

.word-bank-drawer__body {
  min-height: 0;
  overflow: auto;
  padding: var(--space-5);
  overscroll-behavior: contain;
}

.word-bank-search {
  display: grid;
  gap: var(--space-2);
}

.word-bank-search label {
  color: var(--text-secondary);
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
}

.word-bank-search input {
  width: 100%;
  min-height: var(--control-height);
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-base);
  color: var(--text-primary);
}

.word-bank-filters {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-top: var(--space-3);
}

.word-bank-filter {
  min-height: var(--touch-target-min);
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-secondary);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.word-bank-filter.is-active,
.word-bank-filter[aria-pressed="true"] {
  border-color: var(--feedback-info-accent);
  background: var(--feedback-info-soft);
  color: var(--feedback-info-ink);
}

.word-bank-results-summary {
  margin: var(--space-3) 0;
  color: var(--text-muted);
  font-size: var(--text-xs);
}

.word-bank-content,
.word-bank-list {
  display: grid;
  gap: var(--space-2);
}

.word-bank-content {
  gap: var(--space-4);
}

.word-bank-entry {
  width: 100%;
  min-height: var(--touch-target-min);
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: var(--space-2);
  align-items: center;
  padding: var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-base);
  color: var(--text-primary);
  text-align: left;
  cursor: pointer;
}

.word-bank-entry:hover,
.word-bank-entry.is-selected {
  border-color: var(--feedback-info-accent);
  background: var(--feedback-info-soft);
}

.word-bank-entry__copy {
  min-width: 0;
  display: grid;
  gap: 2px;
}

.word-bank-entry__copy strong {
  font-size: var(--text-sm);
}

.word-bank-entry__definition {
  overflow: hidden;
  color: var(--text-secondary);
  font-size: var(--text-xs);
  text-overflow: ellipsis;
  white-space: nowrap;
}

.word-bank-entry__meta {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  color: var(--text-muted);
  font-size: 0.68rem;
  white-space: nowrap;
}

.word-bank-entry__review {
  color: var(--feedback-warning-ink);
  font-weight: var(--weight-bold);
}

.word-bank-empty {
  margin: 0;
  padding: var(--space-4);
  border: 1px dashed var(--border-default);
  border-radius: var(--radius-md);
  color: var(--text-muted);
  text-align: center;
}

.word-bank-detail {
  padding: var(--space-4);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-subtle);
}

.word-bank-detail__heading {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-3);
}

.word-bank-detail__scope {
  color: var(--text-muted);
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.word-bank-detail h3 {
  margin: var(--space-1) 0 0;
  font-size: var(--text-lg);
}

.word-bank-review-toggle {
  min-height: var(--touch-target-min);
  flex: 0 0 auto;
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-secondary);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.word-bank-review-toggle[aria-pressed="true"] {
  border-color: var(--feedback-warning-accent);
  background: var(--feedback-warning-soft);
  color: var(--feedback-warning-ink);
}

.word-bank-detail__grid {
  display: grid;
  gap: var(--space-3);
  margin: var(--space-4) 0 0;
}

.word-bank-detail__grid > div {
  display: grid;
  gap: 3px;
}

.word-bank-detail dt {
  color: var(--text-muted);
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
  text-transform: uppercase;
}

.word-bank-detail dd {
  margin: 0;
  color: var(--text-secondary);
  line-height: var(--leading-normal);
}

.word-bank-detail__notation {
  font-family: var(--font-math);
  color: var(--text-primary) !important;
}

.word-bank-drawer__note {
  margin: var(--space-5) 0 0;
  padding-top: var(--space-4);
  border-top: 1px solid var(--divider-default);
  color: var(--text-muted);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
}

.activity-frame {
  min-height: 0;
  padding: var(--space-4);
  background: var(--surface-canvas);
  overflow: hidden;
}

.activity-stage {
  height: 100%;
  min-height: 0;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr);
  gap: var(--space-4);
  padding: var(--space-5);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-base);
  overflow: auto;
  overscroll-behavior: contain;
}

.activity-stage__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.activity-chip {
  display: inline-flex;
  align-items: center;
  min-height: 30px;
  padding: 0 var(--space-3);
  border-radius: var(--radius-pill);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
}

.activity-position {
  color: var(--text-muted);
  font-size: var(--text-sm);
  font-variant-numeric: tabular-nums;
}

.activity-stage__content {
  min-height: 0;
  display: grid;
  grid-template-columns: minmax(260px, 0.8fr) minmax(380px, 1.2fr);
  gap: clamp(var(--space-5), 4vw, var(--space-7));
  align-items: center;
}

.activity-copy {
  max-width: 560px;
}

.activity-copy h2 {
  margin: var(--space-2) 0 var(--space-4);
  font-size: clamp(1.75rem, 3vw, 2.65rem);
  line-height: 1.08;
  letter-spacing: -0.04em;
}

.activity-copy > p:not(.activity-overline) {
  margin: 0;
  color: var(--text-secondary);
  font-size: var(--text-md);
  line-height: var(--leading-relaxed);
}

.activity-callout {
  margin-top: var(--space-5);
  padding: var(--space-4);
  border-left: 4px solid var(--mode-accent);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  background: var(--mode-soft);
  color: var(--mode-soft-text);
}

.activity-callout p {
  margin: var(--space-2) 0 0;
  line-height: var(--leading-normal);
}

.math-placeholder {
  position: relative;
  min-height: 330px;
  height: min(46vh, 470px);
  display: grid;
  place-items: center;
  align-content: center;
  gap: var(--space-3);
  overflow: hidden;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-xl);
  background: var(--surface-base);
}

.math-placeholder__grid {
  position: absolute;
  inset: 0;
  opacity: 0.6;
  background-image:
    linear-gradient(to right, var(--divider-default) 1px, transparent 1px),
    linear-gradient(to bottom, var(--divider-default) 1px, transparent 1px);
  background-size: 36px 36px;
  mask-image: linear-gradient(to bottom, transparent 0%, black 15%, black 85%, transparent 100%);
}

.math-placeholder__formula,
.math-placeholder__caption {
  position: relative;
  z-index: 1;
}

.math-placeholder__formula {
  padding: var(--space-3) var(--space-5);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-base);
  box-shadow: var(--shadow-raised);
  font-family: var(--font-math);
  font-size: clamp(2rem, 5vw, 4rem);
  line-height: 1.15;
}

.math-placeholder__caption {
  max-width: 420px;
  margin: 0;
  padding: 0 var(--space-4);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
  text-align: center;
}

.activity-controls {
  min-height: 72px;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-3) var(--space-5);
  border-top: 1px solid var(--divider-default);
  background: var(--surface-base);
}

.activity-button {
  min-height: var(--touch-target-min);
  min-width: 124px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: 0 var(--space-4);
  border-radius: var(--radius-md);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.activity-button--secondary {
  justify-self: start;
  border: 1px solid var(--border-default);
  background: var(--surface-base);
}

.activity-button--primary {
  justify-self: end;
  border: 1px solid var(--mode-accent);
  background: var(--mode-accent);
  color: var(--mode-accent-text);
}

.activity-controls__summary {
  display: grid;
  gap: var(--space-1);
  text-align: center;
}

.activity-controls__summary strong {
  font-size: var(--text-sm);
  font-variant-numeric: tabular-nums;
}

/* Compact desktop / landscape tablet: retain the two-column shell but reduce chrome. */
@media (max-width: 1100px) and (min-width: 901px) {
  .app-shell__topbar {
    grid-template-columns: minmax(150px, 0.7fr) minmax(300px, 1.8fr) minmax(130px, 0.6fr);
    padding-left: var(--space-4);
    padding-right: var(--space-4);
  }

  .app-shell__body {
    grid-template-columns: 200px minmax(0, 1fr);
    gap: var(--space-3);
    padding: var(--space-3);
  }

  .workspace-header {
    gap: var(--space-3);
    padding-left: var(--space-4);
    padding-right: var(--space-4);
  }

  .workspace-header h1 {
    font-size: var(--text-lg);
  }

  .mode-tabs {
    width: min(100%, 470px);
  }

  .mode-tab {
    gap: var(--space-1);
    padding-left: var(--space-1);
    padding-right: var(--space-1);
  }

  .mode-tab__icon {
    width: 18px;
    height: 18px;
  }

  .mode-tab__sublabel {
    display: none;
  }

  .activity-stage {
    padding: var(--space-4);
  }

  .activity-stage__content {
    grid-template-columns: minmax(230px, 0.8fr) minmax(300px, 1.2fr);
    gap: var(--space-5);
  }

  .activity-copy h2 {
    font-size: clamp(1.65rem, 3vw, 2.2rem);
  }

  .math-placeholder {
    min-height: 300px;
  }
}

/* Tablet / compact shell: topic navigation becomes one shared overlay drawer. */
@media (max-width: 900px) {
  .app-shell__topbar {
    grid-template-areas: "brand nav-toggle context";
    grid-template-columns: auto auto minmax(0, 1fr);
    gap: var(--space-3);
    padding: var(--space-3) var(--space-4);
  }

  .topic-navigation-toggle {
    display: inline-flex;
  }

  .topbar__context {
    justify-content: flex-end;
  }

  .topbar__status {
    display: none;
  }

  .app-shell__body {
    grid-template-columns: minmax(0, 1fr);
    gap: 0;
    padding: var(--space-3);
  }

  .navigation-scrim {
    position: fixed;
    inset: 0;
    z-index: 20;
    width: 100%;
    height: 100%;
    border: 0;
    background: var(--overlay-scrim);
    cursor: pointer;
  }

  .navigation-scrim:not([hidden]) {
    display: block;
  }

  .topic-navigation {
    position: fixed;
    inset: 0 auto 0 0;
    z-index: 30;
    width: min(320px, calc(100vw - 48px));
    max-width: 100%;
    padding: var(--space-5) var(--space-4);
    border: 0;
    border-right: 1px solid var(--border-default);
    border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
    box-shadow: var(--shadow-drawer);
    transform: translateX(calc(-100% - var(--space-4)));
    visibility: hidden;
    transition:
      transform var(--motion-normal) var(--motion-easing),
      visibility 0s linear var(--motion-normal);
  }

  .app-shell[data-navigation-open="true"] .topic-navigation {
    transform: translateX(0);
    visibility: visible;
    transition-delay: 0s;
  }

  .topic-navigation__close {
    display: grid;
  }

  .learning-workspace {
    height: 100%;
  }

  .workspace-header,
  .activity-stage {
    padding-left: var(--space-4);
    padding-right: var(--space-4);
  }

  .workspace-header {
    gap: var(--space-3);
  }

  .workspace-header h1 {
    font-size: var(--text-lg);
  }

  .mode-tabs {
    width: min(100%, 500px);
  }

  .mode-tab {
    gap: var(--space-1);
    padding-left: var(--space-2);
    padding-right: var(--space-2);
  }

  .mode-tab__sublabel {
    display: none;
  }

  .activity-stage__content {
    grid-template-columns: minmax(210px, 0.8fr) minmax(300px, 1.2fr);
    gap: var(--space-5);
  }

  .activity-copy h2 {
    font-size: clamp(1.55rem, 3vw, 2.1rem);
  }

  .activity-copy > p:not(.activity-overline) {
    font-size: var(--text-base);
  }

  .math-placeholder {
    min-height: 280px;
    height: min(42vh, 420px);
  }
}

/* Narrow screen: keep the shell fixed; stack only the activity and let that panel scroll. */
@media (max-width: 680px) {
  .app-shell__topbar {
    grid-template-areas:
      "brand nav-toggle"
      "context context";
    grid-template-columns: minmax(0, 1fr) auto;
    row-gap: var(--space-2);
    padding: var(--space-2) var(--space-3) var(--space-3);
  }

  .brand {
    gap: var(--space-2);
  }

  .brand__mark {
    width: 34px;
    height: 34px;
  }

  .topic-navigation-toggle {
    justify-self: end;
    min-height: var(--touch-target-min);
  }

  .topbar__context {
    justify-content: space-between;
    gap: var(--space-2);
  }

  .breadcrumb {
    font-size: var(--text-sm);
  }

  .scope-badge {
    min-height: 28px;
    padding-left: var(--space-2);
    padding-right: var(--space-2);
    font-size: 0.68rem;
  }

  .app-shell__body {
    padding: var(--space-2);
  }

  .topic-navigation {
    width: min(304px, calc(100vw - 32px));
  }

  .learning-workspace {
    border-radius: var(--radius-md);
  }

  .workspace-header {
    align-items: stretch;
    flex-direction: column;
    gap: var(--space-2);
    padding: var(--space-3);
  }

  .workspace-header h1 {
    margin-top: 2px;
    font-size: var(--text-md);
  }

  .mode-tabs {
    width: 100%;
    max-width: none;
    gap: 3px;
    padding: 3px;
  }

  .mode-tab {
    min-height: 46px;
    flex-direction: column;
    gap: 2px;
    padding: var(--space-1) 2px;
  }

  .mode-tab__icon {
    width: 17px;
    height: 17px;
  }

  .mode-tab__text {
    display: block;
    text-align: center;
  }

  .mode-tab__label {
    font-size: 0.62rem;
    letter-spacing: -0.01em;
  }

  .mode-tab__sublabel {
    display: none;
  }

  .activity-frame {
    padding: var(--space-2);
  }

  .activity-stage {
    gap: var(--space-3);
    padding: var(--space-3);
  }

  .activity-stage__header {
    align-items: flex-start;
  }

  .activity-stage__tools {
    gap: var(--space-2);
  }

  .activity-help-button {
    min-height: var(--touch-target-min);
    padding: 0 var(--space-2);
    font-size: var(--text-xs);
  }

  .activity-help-button__icon {
    display: none;
  }

  .help-drawer {
    width: min(392px, calc(100% - var(--space-3)));
    border-radius: var(--radius-lg) 0 0 var(--radius-lg);
  }

  .help-drawer__header,
  .help-drawer__body {
    padding: var(--space-4);
  }

  .activity-stage__content {
    grid-template-columns: minmax(0, 1fr);
    gap: var(--space-5);
    align-content: start;
  }

  .activity-copy {
    max-width: none;
  }

  .activity-copy h2 {
    margin-bottom: var(--space-3);
    font-size: clamp(1.55rem, 7vw, 2rem);
  }

  .activity-copy > p:not(.activity-overline) {
    font-size: var(--text-base);
    line-height: var(--leading-normal);
  }

  .activity-callout {
    margin-top: var(--space-4);
    padding: var(--space-3);
  }

  .math-placeholder {
    min-height: 280px;
    height: auto;
    padding: var(--space-7) var(--space-3);
  }

  .math-placeholder__formula {
    max-width: 100%;
    overflow-wrap: anywhere;
    padding-left: var(--space-3);
    padding-right: var(--space-3);
    font-size: clamp(2rem, 12vw, 3.25rem);
    text-align: center;
  }

  .activity-controls {
    min-height: 62px;
    grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
    gap: var(--space-2);
    padding: var(--space-2) var(--space-3);
  }

  .activity-button {
    min-width: 0;
    width: 100%;
    padding: 0 var(--space-2);
  }

  .activity-controls__summary .eyebrow {
    display: none;
  }

  .activity-controls__summary strong {
    white-space: nowrap;
  }
}



@media (max-width: 680px) {
  .word-bank-button {
    min-height: var(--touch-target-min);
    padding: 0 var(--space-2);
  }

  .word-bank-button__label {
    display: none;
  }

  .word-bank-drawer {
    width: min(100%, 460px);
    border-radius: var(--radius-lg) 0 0 var(--radius-lg);
  }

  .word-bank-drawer__header,
  .word-bank-drawer__body {
    padding: var(--space-4);
  }

  .word-bank-detail__heading {
    align-items: stretch;
    flex-direction: column;
  }

  .word-bank-review-toggle {
    align-self: flex-start;
  }

  .vocabulary-popover {
    width: min(280px, calc(100vw - 32px));
  }
}

@media (max-width: 380px) {
  .mode-tab__label {
    font-size: 0.56rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  .topic-navigation,
  .help-drawer,
  .word-bank-drawer,
  .vocabulary-popover {
    transition: none;
  }
}

/* Step 14: versioned local progress/security data controls */
.topic-navigation__actions {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
}

.data-management-trigger,
.data-management-dialog__close,
.data-management-button {
  min-height: var(--touch-target-min);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-base);
  color: var(--text-secondary);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.data-management-trigger {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 0 var(--space-2);
  min-height: var(--touch-target-min);
  font-size: var(--text-xs);
}

.data-management-trigger:hover,
.data-management-button--secondary:hover,
.data-management-dialog__close:hover {
  background: var(--surface-subtle);
  color: var(--text-primary);
}

.data-management-dialog {
  width: min(720px, calc(100vw - 32px));
  max-height: min(760px, calc(100dvh - 32px));
  padding: 0;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-raised);
  color: var(--text-primary);
  box-shadow: var(--shadow-drawer);
}

.data-management-dialog::backdrop {
  background: var(--overlay-scrim);
}

.data-management-dialog__panel {
  display: grid;
  gap: var(--space-5);
  padding: var(--space-5);
  overflow: auto;
  max-height: inherit;
}

.data-management-dialog__header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-4);
}

.data-management-dialog__header h2 {
  margin: var(--space-1) 0 0;
  font-size: var(--text-xl);
}

.data-management-dialog__close {
  width: var(--touch-target-min);
  height: var(--touch-target-min);
  padding: 0;
  font-size: var(--text-xl);
  line-height: 1;
}

.data-management-dialog__intro,
.data-management-card p,
.data-management-status {
  margin: 0;
  color: var(--text-secondary);
  line-height: 1.5;
}

.data-management-summary {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: var(--space-2);
}

.data-management-summary > div {
  display: grid;
  gap: var(--space-1);
  min-width: 0;
  padding: var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-subtle);
}

.data-management-summary__label {
  color: var(--text-muted);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.data-management-summary strong {
  font-size: var(--text-sm);
  overflow-wrap: anywhere;
}

.data-management-actions {
  display: grid;
  gap: var(--space-3);
}

.data-management-card {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: var(--space-4);
  align-items: center;
  padding: var(--space-4);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-base);
}

.data-management-card h3 {
  margin: 0 0 var(--space-1);
  font-size: var(--text-base);
}

.data-management-card--danger {
  border-color: var(--feedback-incorrect-soft);
}

.data-management-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0 var(--space-4);
  white-space: nowrap;
}

.data-management-button:not(.data-management-button--secondary):not(.data-management-button--danger) {
  border-color: var(--feedback-info-accent);
  background: var(--feedback-info-accent);
  color: var(--surface-base);
}

.data-management-button--danger {
  border-color: var(--feedback-incorrect-accent);
  background: var(--feedback-incorrect-soft);
  color: var(--feedback-incorrect-ink);
}

.data-import-controls {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: var(--space-2);
  flex-wrap: wrap;
}

.data-import-filename {
  max-width: 210px;
  color: var(--text-muted);
  font-size: var(--text-xs);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.data-import-preview,
.data-reset-confirmation {
  grid-column: 1 / -1;
  display: grid;
  gap: var(--space-2);
  padding: var(--space-3);
  border-radius: var(--radius-md);
  background: var(--feedback-info-soft);
}

.data-reset-confirmation {
  background: var(--feedback-incorrect-soft);
  color: var(--feedback-incorrect-ink);
}

.data-reset-confirmation > div {
  display: flex;
  gap: var(--space-2);
  flex-wrap: wrap;
}

.data-management-status {
  min-height: 1.5em;
  font-size: var(--text-sm);
}

@media (max-width: 680px) {
  .data-management-dialog {
    width: calc(100vw - 16px);
    max-height: calc(100dvh - 16px);
    border-radius: var(--radius-md);
  }

  .data-management-dialog__panel {
    gap: var(--space-4);
    padding: var(--space-4);
  }

  .data-management-summary {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .data-management-card {
    grid-template-columns: minmax(0, 1fr);
  }

  .data-management-card > .data-management-button,
  .data-import-controls {
    justify-self: stretch;
  }

  .data-import-controls {
    justify-content: flex-start;
  }
}

/* Step 22: reusable ClassWiz calculator support */
.classwiz-support-button {
  min-height: var(--touch-target-min);
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.classwiz-support-button:hover {
  border-color: var(--feedback-info-accent);
  background: var(--feedback-info-soft);
  color: var(--feedback-info-ink);
}

.classwiz-support-button__icon {
  min-width: 24px;
  height: 22px;
  display: inline-grid;
  place-items: center;
  padding: 0 5px;
  border-radius: var(--radius-sm);
  background: var(--surface-subtle);
  color: var(--text-primary);
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
  font-style: italic;
}

.classwiz-support-scrim {
  position: absolute;
  inset: 0;
  z-index: 40;
  width: 100%;
  height: 100%;
  border: 0;
  background: var(--overlay-scrim);
  opacity: 0.72;
  cursor: pointer;
}

.classwiz-support-scrim:not([hidden]) { display: block; }

.classwiz-support-panel {
  position: absolute;
  inset: 0 0 0 auto;
  z-index: 50;
  width: min(500px, calc(100% - 56px));
  min-width: 0;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr);
  border-left: 1px solid var(--border-default);
  border-radius: var(--radius-lg) 0 0 var(--radius-lg);
  background: var(--surface-base);
  box-shadow: var(--shadow-drawer);
  transform: translateX(calc(100% + var(--space-4)));
  visibility: hidden;
  transition: transform var(--motion-normal) var(--motion-easing), visibility 0s linear var(--motion-normal);
}

.app-shell[data-classwiz-open="true"] .classwiz-support-panel {
  transform: translateX(0);
  visibility: visible;
  transition-delay: 0s;
}

.classwiz-support-panel__header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-4);
  padding: var(--space-4) var(--space-5);
  border-bottom: 1px solid var(--divider-default);
}

.classwiz-support-panel__header .eyebrow { margin: 0; }
.classwiz-support-panel__header h2 {
  margin: var(--space-1) 0 0;
  font-size: var(--text-xl);
  letter-spacing: -0.025em;
}

.classwiz-support-panel__close {
  width: var(--touch-target-min);
  height: var(--touch-target-min);
  flex: 0 0 auto;
  display: grid;
  place-items: center;
  border: 1px solid transparent;
  border-radius: var(--radius-pill);
  background: var(--surface-subtle);
  color: var(--text-secondary);
  font-size: var(--text-xl);
  line-height: 1;
  cursor: pointer;
}

.classwiz-support-panel__close:hover {
  border-color: var(--border-default);
  background: var(--surface-base);
  color: var(--text-primary);
}

.classwiz-support-panel__body {
  min-height: 0;
  overflow: auto;
  padding: var(--space-5);
  overscroll-behavior: contain;
}

.classwiz-support-panel__intro,
.classwiz-support-panel__return-note,
.classwiz-support-section p {
  color: var(--text-secondary);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
}

.classwiz-support-panel__intro { margin: 0 0 var(--space-4); }

.classwiz-use-case-tabs,
.classwiz-model-tabs {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.classwiz-use-case-tabs button,
.classwiz-model-tabs button {
  min-height: var(--touch-target-min);
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-base);
  color: var(--text-secondary);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.classwiz-use-case-tabs button[aria-selected="true"],
.classwiz-model-tabs button[aria-selected="true"] {
  border-color: var(--feedback-info-accent);
  background: var(--feedback-info-soft);
  color: var(--feedback-info-ink);
}

.classwiz-support-section {
  margin-top: var(--space-4);
  padding: var(--space-4);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-subtle);
}

.classwiz-support-section__heading {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-3);
}

.classwiz-support-section__heading > strong { font-size: var(--text-sm); }
.classwiz-support-section__eyebrow {
  margin: 0 0 var(--space-2) !important;
  color: var(--text-primary) !important;
  font-size: var(--text-xs) !important;
  font-weight: var(--weight-bold);
  letter-spacing: 0.045em;
  text-transform: uppercase;
}
.classwiz-support-section > p:last-child { margin-bottom: 0; }

.classwiz-example {
  margin-top: var(--space-3);
  padding: var(--space-3);
  border-left: 3px solid var(--feedback-info-accent);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  background: var(--surface-base);
}
.classwiz-example strong { font-size: var(--text-xs); }
.classwiz-example p { margin: var(--space-1) 0 0; }

.classwiz-radians-reminder {
  margin: var(--space-3) 0 0 !important;
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--feedback-warning-accent);
  border-radius: var(--radius-md);
  background: var(--feedback-warning-soft);
  color: var(--feedback-warning-ink) !important;
  font-weight: var(--weight-semibold);
}

.classwiz-steps {
  display: grid;
  gap: var(--space-2);
  margin: var(--space-3) 0 0;
  padding: 0;
  list-style: none;
}
.classwiz-step {
  display: grid;
  grid-template-columns: 30px minmax(0, 1fr);
  gap: var(--space-3);
  align-items: start;
  padding: var(--space-2) 0;
}
.classwiz-step + .classwiz-step { border-top: 1px solid var(--divider-default); }
.classwiz-step__number {
  width: 28px;
  height: 28px;
  display: grid;
  place-items: center;
  border-radius: var(--radius-pill);
  background: var(--feedback-info-soft);
  color: var(--feedback-info-ink);
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
}
.classwiz-step__copy { display: grid; gap: 2px; }
.classwiz-step__copy strong { font-size: var(--text-sm); }
.classwiz-step__copy span {
  color: var(--text-secondary);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
}

.classwiz-support-section--warning { background: var(--surface-base); }
.classwiz-support-panel__return-note {
  margin: var(--space-4) 0 0;
  padding-top: var(--space-3);
  border-top: 1px solid var(--divider-default);
  color: var(--text-muted);
  font-size: var(--text-xs);
}

.app-shell[data-classwiz-open="true"] .vocabulary-popover {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

@media (max-width: 680px) {
  .classwiz-support-button {
    min-height: var(--touch-target-min);
    padding: 0 var(--space-2);
  }
  .classwiz-support-button__label { display: none; }
  .classwiz-support-panel {
    width: min(100%, 480px);
    border-radius: var(--radius-lg) 0 0 var(--radius-lg);
  }
  .classwiz-support-panel__header,
  .classwiz-support-panel__body { padding: var(--space-4); }
}

@media (prefers-reduced-motion: reduce) {
  .classwiz-support-panel { transition: none; }
}

/* Step 37: topics may intentionally implement only a subset of the frozen five modes. */
.mode-tab:disabled,
.mode-tab[aria-disabled="true"] {
  cursor: not-allowed;
  opacity: 0.42;
}


/* Topic objectives pass: intentions → learning → recap → practice. */
.topic-goals-button {
  min-height: var(--touch-target-min);
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.topic-goals-button:hover,
.topic-goals-button:focus-visible {
  border-color: var(--mode-accent);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  outline: none;
}

.topic-goals-button__icon {
  width: 22px;
  height: 22px;
  display: inline-grid;
  place-items: center;
  border-radius: var(--radius-pill);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  font-size: var(--text-sm);
  font-weight: var(--weight-bold);
}

.topic-objectives-card--inline {
  grid-column: 1 / -1;
  display: grid;
  grid-template-columns: minmax(180px, 0.45fr) minmax(0, 1.55fr);
  gap: var(--space-3) var(--space-5);
  align-items: start;
  padding: var(--space-4);
  border: 1px solid var(--mode-accent);
  border-radius: var(--radius-lg);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
}

.topic-objectives-card--inline[hidden] {
  display: none;
}

.topic-objectives-card__heading {
  min-width: 0;
}

.topic-objectives-card__heading .eyebrow {
  color: var(--mode-soft-text);
  opacity: 0.72;
}

.topic-objectives-card__heading h2 {
  margin: var(--space-1) 0 0;
  font-size: var(--text-lg);
  line-height: var(--leading-tight);
  letter-spacing: -0.02em;
}

.topic-objectives-list {
  list-style: none;
  display: grid;
  gap: var(--space-2);
  margin: 0;
  padding: 0;
}

.topic-objectives-list__item {
  display: grid;
  grid-template-columns: 22px minmax(0, 1fr);
  gap: var(--space-2);
  align-items: start;
  line-height: var(--leading-normal);
}

.topic-objectives-list__marker {
  width: 20px;
  height: 20px;
  display: inline-grid;
  place-items: center;
  margin-top: 1px;
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--mode-soft-text);
  font-size: 0.72rem;
  font-weight: var(--weight-bold);
}

.topic-objectives-card__footer {
  grid-column: 1 / -1;
  margin: 0;
  padding-top: var(--space-2);
  border-top: 1px solid color-mix(in srgb, currentColor 22%, transparent);
  color: currentColor;
  font-size: var(--text-xs);
  line-height: var(--leading-normal);
  opacity: 0.8;
}

.topic-goals-dialog {
  width: min(680px, calc(100vw - 32px));
  max-height: min(760px, calc(100dvh - 32px));
  padding: 0;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-raised);
  color: var(--text-primary);
  box-shadow: var(--shadow-drawer);
}

.topic-goals-dialog::backdrop {
  background: var(--overlay-scrim);
}

.topic-goals-dialog__panel {
  display: grid;
  gap: var(--space-4);
  padding: var(--space-5);
  overflow: auto;
  max-height: inherit;
}

.topic-goals-dialog__header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-4);
}

.topic-goals-dialog__header h2 {
  margin: var(--space-1) 0 0;
  font-size: var(--text-xl);
  line-height: var(--leading-tight);
  letter-spacing: -0.025em;
}

.topic-goals-dialog__close {
  width: var(--touch-target-min);
  height: var(--touch-target-min);
  flex: 0 0 auto;
  display: grid;
  place-items: center;
  padding: 0;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-subtle);
  color: var(--text-secondary);
  font-size: var(--text-xl);
  cursor: pointer;
}

.topic-goals-dialog__close:hover,
.topic-goals-dialog__close:focus-visible {
  border-color: var(--mode-accent);
  color: var(--text-primary);
  outline: none;
}

.topic-goals-dialog__topic {
  margin: 0;
  color: var(--text-secondary);
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
}

.topic-objectives-list--dialog {
  gap: var(--space-3);
  padding: var(--space-4);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-subtle);
}

.topic-objectives-list--dialog .topic-objectives-list__marker {
  border: 1px solid var(--mode-accent);
  background: var(--mode-soft);
}

.topic-goals-dialog .topic-objectives-card__footer {
  color: var(--text-muted);
}

@media (max-width: 900px) {
  .topic-objectives-card--inline {
    grid-template-columns: minmax(150px, 0.4fr) minmax(0, 1.6fr);
    gap: var(--space-3);
  }
}

@media (max-width: 680px) {
  .topic-goals-button {
    padding: 0 var(--space-2);
  }

  .topic-goals-button__label {
    display: none;
  }

  .topic-objectives-card--inline {
    grid-template-columns: minmax(0, 1fr);
    padding: var(--space-3);
  }

  .topic-objectives-card__footer {
    grid-column: 1;
  }

  .topic-goals-dialog {
    width: calc(100vw - 16px);
    max-height: calc(100dvh - 16px);
    border-radius: var(--radius-md);
  }

  .topic-goals-dialog__panel {
    gap: var(--space-3);
    padding: var(--space-4);
  }

  .topic-objectives-list--dialog {
    padding: var(--space-3);
  }
}

/* Understand journey bookends: goals are a true opening page and progression is a true closing page. */
[data-standard-activity-content][data-understand-journey-page="goals"],
[data-standard-activity-content][data-understand-journey-page="pathway"] {
  grid-template-columns: minmax(0, 1fr);
  align-content: start;
}

[data-standard-activity-content][data-understand-journey-page="goals"] > .activity-copy,
[data-standard-activity-content][data-understand-journey-page="goals"] > .math-placeholder,
[data-standard-activity-content][data-understand-journey-page="pathway"] > .activity-copy,
[data-standard-activity-content][data-understand-journey-page="pathway"] > .math-placeholder {
  display: none;
}

[data-standard-activity-content][data-understand-journey-page="goals"] .topic-objectives-card--inline {
  width: min(100%, 920px);
  justify-self: center;
  padding: clamp(var(--space-4), 4vw, var(--space-7));
  grid-template-columns: minmax(210px, 0.5fr) minmax(0, 1.5fr);
  gap: var(--space-5) var(--space-7);
  border-radius: var(--radius-xl);
}

[data-standard-activity-content][data-understand-journey-page="goals"] .topic-objectives-card__heading h2 {
  font-size: clamp(1.65rem, 3vw, 2.4rem);
}

[data-standard-activity-content][data-understand-journey-page="goals"] .topic-objectives-list {
  gap: var(--space-3);
  font-size: var(--text-md);
}

.topic-pathway-card {
  width: min(100%, 940px);
  justify-self: center;
  display: grid;
  gap: var(--space-5);
  padding: clamp(var(--space-4), 4vw, var(--space-7));
  border: 1px solid var(--border-default);
  border-radius: var(--radius-xl);
  background: var(--surface-raised);
  box-shadow: var(--shadow-raised);
}

.topic-pathway-card[hidden] {
  display: none;
}

.topic-pathway-card__heading {
  display: grid;
  gap: var(--space-2);
}

.topic-pathway-card__heading h2 {
  margin: 0;
  font-size: clamp(1.7rem, 3.2vw, 2.55rem);
  line-height: var(--leading-tight);
  letter-spacing: -0.03em;
}

.topic-pathway-card__heading p:last-child {
  max-width: 760px;
  margin: 0;
  color: var(--text-secondary);
  line-height: var(--leading-relaxed);
}

.topic-pathway-list {
  list-style: none;
  display: grid;
  gap: var(--space-3);
  margin: 0;
  padding: 0;
}

.topic-pathway-step {
  display: grid;
  grid-template-columns: 40px minmax(0, 1fr) auto;
  gap: var(--space-3);
  align-items: center;
  padding: var(--space-3) var(--space-4);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-subtle);
}

.topic-pathway-step[hidden] {
  display: none;
}

.topic-pathway-step__number {
  width: 34px;
  height: 34px;
  display: inline-grid;
  place-items: center;
  border-radius: var(--radius-pill);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  font-weight: var(--weight-bold);
}

.topic-pathway-step > div {
  min-width: 0;
  display: grid;
  gap: var(--space-1);
}

.topic-pathway-step > div strong {
  font-size: var(--text-md);
}

.topic-pathway-step > div span {
  color: var(--text-secondary);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
}

.topic-pathway-step__button,
.topic-pathway-revisit {
  min-height: var(--touch-target-min);
  padding: 0 var(--space-4);
  border-radius: var(--radius-md);
  font-weight: var(--weight-semibold);
  cursor: pointer;
}

.topic-pathway-step__button {
  border: 1px solid var(--mode-accent);
  background: var(--mode-accent);
  color: var(--mode-accent-text);
}

.topic-pathway-revisit {
  border: 1px solid var(--border-default);
  background: var(--surface-base);
  color: var(--text-primary);
}

.topic-pathway-step__button:hover,
.topic-pathway-step__button:focus-visible,
.topic-pathway-revisit:hover,
.topic-pathway-revisit:focus-visible {
  outline: none;
  box-shadow: 0 0 0 var(--focus-ring-width) color-mix(in srgb, var(--mode-accent) 22%, transparent);
}

.topic-pathway-card__footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  padding-top: var(--space-3);
  border-top: 1px solid var(--divider-default);
}

.topic-pathway-card__footer p {
  margin: 0;
  color: var(--text-secondary);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
}

.activity-button:disabled,
.activity-button[aria-disabled="true"] {
  cursor: default;
  opacity: 0.42;
}

@media (max-width: 680px) {
  [data-standard-activity-content][data-understand-journey-page="goals"] .topic-objectives-card--inline {
    grid-template-columns: minmax(0, 1fr);
    gap: var(--space-4);
  }

  .topic-pathway-step {
    grid-template-columns: 36px minmax(0, 1fr);
  }

  .topic-pathway-step__button {
    grid-column: 1 / -1;
    width: 100%;
  }

  .topic-pathway-card__footer {
    align-items: stretch;
    flex-direction: column;
  }

  .topic-pathway-revisit {
    width: 100%;
  }
}

/* Shared responsive refinements for real Understand experiences. */
.activity-stage__content[data-custom-understand-active="true"] .activity-copy h2 {
  margin-bottom: var(--space-2);
  font-size: clamp(1.45rem, 2.4vw, 2.15rem);
}

.activity-stage__content[data-custom-understand-active="true"] .activity-callout {
  margin-top: var(--space-3);
  padding: var(--space-3);
}

/* Keep dense shared visual systems readable before they reach phone breakpoints. */
@media (max-width: 1180px) {
  .activity-stage__content[data-custom-understand-active="true"] .linked-gradient-explorer__graphs {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .activity-stage__content[data-custom-understand-active="true"] .family-curves-explorer__controls {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .activity-stage__content[data-custom-understand-active="true"] .family-curves-explorer__readout {
    grid-column: 1 / -1;
    justify-content: flex-start;
  }

  .activity-stage__content[data-custom-understand-active="true"] .area-explorer__controls,
  .activity-stage__content[data-custom-understand-active="true"] .rectangle-sum-explorer__controls {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 820px) {
  .activity-stage__content[data-custom-understand-active="true"] .linked-gradient-explorer__graphs,
  .activity-stage__content[data-custom-understand-active="true"] .family-curves-explorer__graphs {
    grid-template-columns: minmax(0, 1fr);
  }

  .activity-stage__content[data-custom-understand-active="true"] .area-explorer__controls,
  .activity-stage__content[data-custom-understand-active="true"] .area-explorer__limit-controls,
  .activity-stage__content[data-custom-understand-active="true"] .area-explorer__readout,
  .activity-stage__content[data-custom-understand-active="true"] .rectangle-sum-explorer__controls,
  .activity-stage__content[data-custom-understand-active="true"] .rectangle-sum-explorer__bounds,
  .activity-stage__content[data-custom-understand-active="true"] .rectangle-sum-explorer__readout,
  .activity-stage__content[data-custom-understand-active="true"] .rectangle-sum-explorer__component-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .activity-stage__content[data-custom-understand-active="true"] .trig-first-principles__diagram-grid {
    grid-template-columns: minmax(0, 1fr);
  }
}

/* Visual audit: real Understand experiences must not inherit the fixed mock-placeholder box. */
.understand-visual-host {
  width: 100%;
  min-width: 0;
  min-height: 0;
}
.understand-visual-host[hidden] { display: none; }
.understand-visual-host > * {
  min-width: 0;
  max-width: 100%;
  height: auto !important;
  max-height: none;
  overflow: visible;
}

.activity-stage__content[data-custom-understand-active="true"] {
  grid-template-columns: minmax(220px, .44fr) minmax(0, 1.56fr);
  gap: var(--space-5);
  align-items: start;
}

.activity-stage__content[data-custom-understand-active="true"] .activity-copy {
  align-self: start;
}

.activity-stage__content[data-custom-understand-active="true"] .math-placeholder {
  min-width: 0;
  min-height: 0;
  height: auto;
  display: block;
  overflow: visible;
  border: 0;
  border-radius: 0;
  background: transparent;
}

.activity-stage__content[data-custom-understand-active="true"] .math-placeholder__grid,
.activity-stage__content[data-custom-understand-active="true"] .math-placeholder__formula,
.activity-stage__content[data-custom-understand-active="true"] .math-placeholder__caption {
  display: none;
}

@media (max-width: 1100px) {
  .activity-stage__content[data-custom-understand-active="true"] {
    grid-template-columns: minmax(0, 1fr);
    align-content: start;
  }
  .activity-stage__content[data-custom-understand-active="true"] .activity-copy {
    position: static;
    max-width: 78ch;
  }
}

@media (max-width: 680px) {
  .activity-stage__content[data-custom-understand-active="true"] {
    gap: var(--space-4);
  }
}



/* Manual audit 2026-09-28: collapsible workspace tools + structural AO space recovery. */
[data-activity-controls][hidden],
.activity-stage__tools[hidden] {
  display: none !important;
}

html[data-learning-mode="ao1"] .activity-controls,
html[data-learning-mode="ao2"] .activity-controls,
html[data-learning-mode="ao3"] .activity-controls {
  display: none !important;
}

html[data-learning-mode="ao1"] .activity-position,
html[data-learning-mode="ao2"] .activity-position,
html[data-learning-mode="ao3"] .activity-position {
  display: none !important;
}

.activity-stage__header[data-workspace-tools-bar] {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: var(--space-3);
  min-height: 44px;
}

.workspace-tools__identity {
  min-width: 0;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.activity-stage__header[data-workspace-tools-bar] .activity-stage__tools {
  min-width: 0;
  justify-self: end;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: var(--space-2);
}

.workspace-tools-toggle {
  min-height: 36px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-secondary);
  font: inherit;
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  cursor: pointer;
  white-space: nowrap;
}

.workspace-tools-toggle:hover,
.workspace-tools-toggle:focus-visible {
  border-color: var(--mode-accent);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  outline: none;
}

.workspace-tools-toggle__icon {
  font-size: 0.9rem;
  line-height: 1;
}

.activity-stage[data-workspace-tools-collapsed="true"] {
  gap: var(--space-2);
  padding-top: var(--space-3);
}

.activity-stage[data-workspace-tools-collapsed="true"] .activity-stage__header[data-workspace-tools-bar] {
  grid-template-columns: minmax(0, 1fr) auto;
  min-height: 36px;
}

.activity-stage[data-workspace-tools-collapsed="true"] .workspace-tools__identity {
  min-height: 32px;
}

.activity-stage[data-workspace-tools-collapsed="true"] .workspace-tools-toggle {
  min-height: 32px;
  padding-inline: var(--space-2);
}

@media (max-width: 900px) {
  .activity-stage__header[data-workspace-tools-bar] {
    grid-template-columns: minmax(0, 1fr) auto;
  }

  .activity-stage__header[data-workspace-tools-bar] .activity-stage__tools {
    grid-column: 1 / -1;
    justify-self: stretch;
    justify-content: flex-start;
  }
}

@media (max-width: 680px) {
  .workspace-tools-toggle {
    min-width: 72px;
  }

  .activity-stage__header[data-workspace-tools-bar] .activity-stage__tools {
    overflow-x: auto;
    flex-wrap: nowrap;
    padding-bottom: 2px;
  }

  .activity-stage__header[data-workspace-tools-bar] .activity-stage__tools > * {
    flex: 0 0 auto;
  }
}

/* Workspace chrome: the mode tabs already identify the active mode, so do not repeat
   the mode name or activity count inside the activity stage. */
.workspace-tools__identity {
  display: none;
}

.activity-stage__header[data-workspace-tools-bar] {
  justify-content: flex-end;
}

/* Adaptive viewport density.
   The browser viewport, not the physical monitor resolution, decides how much chrome
   the interface can afford. Touch targets and body text keep their accessible minimums. */
html[data-ui-density="compact"] {
  --space-4: 0.875rem;
  --space-5: 1.125rem;
  --space-6: 1.5rem;
  --space-7: 2.25rem;
  --space-8: 3rem;
  --text-md: 1.0625rem;
  --text-lg: 1.1875rem;
  --text-xl: 1.375rem;
  --text-2xl: 1.875rem;
}

html[data-ui-density="tight"] {
  --space-3: 0.625rem;
  --space-4: 0.75rem;
  --space-5: 1rem;
  --space-6: 1.25rem;
  --space-7: 1.75rem;
  --space-8: 2.5rem;
  --text-md: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.625rem;
}

html[data-ui-density="compact"] .app-shell__topbar { min-height: 56px; }
html[data-ui-density="tight"] .app-shell__topbar { min-height: 52px; }

html[data-ui-density="compact"] .mode-tab__sublabel,
html[data-ui-density="tight"] .mode-tab__sublabel { display: none; }

html[data-ui-density="compact"] .activity-stage__tools,
html[data-ui-density="tight"] .activity-stage__tools { gap: var(--space-2); }

html[data-ui-density="compact"] .math-placeholder {
  min-height: 260px;
  height: min(40vh, 380px);
}
html[data-ui-density="tight"] .math-placeholder {
  min-height: 210px;
  height: min(36vh, 320px);
}

html[data-ui-density="compact"] .activity-controls { min-height: 64px; }
html[data-ui-density="tight"] .activity-controls {
  min-height: 56px;
  padding-top: var(--space-1);
  padding-bottom: var(--space-1);
}

html[data-ui-density="compact"] .question-shell__math { min-height: 108px; }
html[data-ui-density="tight"] .question-shell__math {
  min-height: 84px;
  padding: var(--space-2);
  font-size: clamp(1.45rem, 3vw, 2.2rem);
}
html[data-ui-density="tight"] .question-shell__body {
  gap: var(--space-2);
  padding: var(--space-2);
}
html[data-ui-density="tight"] .question-shell__prompt {
  gap: var(--space-2);
  padding: var(--space-3);
}
html[data-ui-density="tight"] .question-shell__response { gap: var(--space-2); }
html[data-ui-density="tight"] .question-response-textarea { min-height: 96px; }

html[data-ui-density="compact"] .memory-flashcard { min-height: 230px; }
html[data-ui-density="tight"] .memory-flashcard { min-height: 200px; }
html[data-ui-density="compact"] .memory-diagram-recall__canvas { min-height: 250px; }
html[data-ui-density="tight"] .memory-diagram-recall__canvas { min-height: 210px; }
html[data-ui-density="tight"] .memory-panel-heading { margin-bottom: var(--space-3); }

@media (min-width: 681px) {
  html[data-ui-density="tight"] .workspace-header h1 { display: none; }
  html[data-ui-density="tight"] .workspace-header {
    padding-top: var(--space-2);
    padding-bottom: var(--space-2);
  }
}

@media (min-width: 901px) {
  html[data-ui-density="tight"] .topbar__status { display: none; }
  html[data-ui-density="tight"] .app-shell__topbar {
    grid-template-areas: "brand context";
    grid-template-columns: minmax(160px, 0.75fr) minmax(320px, 2fr);
  }
}

@media (min-width: 1101px) {
  html[data-ui-density="compact"] .app-shell__body {
    grid-template-columns: 224px minmax(0, 1fr);
  }
  html[data-ui-density="tight"] .app-shell__body {
    grid-template-columns: 208px minmax(0, 1fr);
  }
}

/* Vertical space recovery pass: keep navigation chrome shallow and give the active
   learning surface first claim on the viewport. */
.app-shell__topbar {
  min-height: 52px;
  padding: var(--space-2) var(--space-4);
}

.brand__mark {
  width: 32px;
  height: 32px;
}

.scope-badge {
  min-height: 26px;
}

.app-shell__body {
  gap: var(--space-3);
  padding: var(--space-2) var(--space-3);
}

.workspace-header {
  position: relative;
  z-index: 8;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  min-height: 54px;
  padding: var(--space-1) var(--space-3);
}

.workspace-topic-title {
  flex: 0 1 220px;
  min-width: 0;
  margin: 0;
  overflow: hidden;
  color: var(--text-primary);
  font-size: var(--text-md);
  font-weight: var(--weight-bold);
  line-height: var(--leading-tight);
  letter-spacing: -0.02em;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.workspace-header__controls {
  min-width: 0;
  flex: 1 1 auto;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: var(--space-2);
}

.mode-tabs {
  width: min(100%, 520px);
  gap: 2px;
  padding: 2px;
}

.mode-tab {
  min-height: var(--touch-target-min);
  gap: 6px;
  padding: var(--space-1) var(--space-2);
}

.mode-tab__text {
  display: block;
  line-height: 1;
  text-align: center;
}

.mode-tab__sublabel {
  display: none !important;
}

.workspace-tools {
  position: relative;
  flex: 0 0 auto;
}

.workspace-tools-toggle {
  min-width: 72px;
  min-height: var(--touch-target-min);
  padding-inline: var(--space-3);
}

.workspace-tools-popover {
  position: absolute;
  top: calc(100% + var(--space-2));
  right: 0;
  z-index: 16;
  width: max-content;
  max-width: min(560px, calc(100vw - 32px));
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: var(--space-2);
  padding: var(--space-2);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background: var(--surface-base);
  box-shadow: var(--shadow-drawer);
}

.activity-frame {
  padding: 0;
  background: var(--surface-base);
}

.activity-stage,
.activity-stage[data-workspace-tools-collapsed="true"] {
  grid-template-rows: minmax(0, 1fr);
  gap: 0;
  padding: 0;
  padding-top: 0;
  border: 0;
  border-radius: 0;
}

.activity-stage__content {
  min-height: 100%;
  padding: var(--space-3) var(--space-4);
}

.activity-controls {
  min-height: 52px;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: var(--space-2);
  padding: var(--space-1) var(--space-3);
}

.activity-controls__summary {
  display: none;
}

.activity-button {
  min-width: 104px;
  min-height: var(--touch-target-min);
  padding-inline: var(--space-3);
}

html[data-ui-density="compact"] .activity-controls,
html[data-ui-density="tight"] .activity-controls {
  min-height: 52px;
}

html[data-ui-density="compact"] .activity-stage__content,
html[data-ui-density="tight"] .activity-stage__content {
  padding-top: var(--space-2);
  padding-bottom: var(--space-2);
}

@media (max-width: 900px) {
  .app-shell__topbar {
    padding: var(--space-2) var(--space-3);
  }

  .workspace-header {
    padding-left: var(--space-2);
    padding-right: var(--space-2);
  }

  .workspace-header__controls {
    gap: var(--space-1);
  }

  .mode-tabs {
    flex: 1 1 auto;
    width: auto;
    max-width: 500px;
  }
}

@media (max-width: 760px) {
  .workspace-topic-title {
    display: none;
  }

  .workspace-header__controls {
    width: 100%;
  }

  .mode-tabs {
    max-width: none;
  }
}

@media (max-width: 680px) {
  .workspace-header {
    min-height: 52px;
    padding: 4px 6px;
  }

  .mode-tab {
    min-height: var(--touch-target-min);
    flex-direction: row;
    gap: 3px;
    padding: 2px 3px;
  }

  .mode-tab__icon {
    width: 15px;
    height: 15px;
  }

  .mode-tab__label {
    font-size: 0.6rem;
  }

  .workspace-tools-toggle {
    min-width: 58px;
    padding-inline: var(--space-2);
  }

  .workspace-tools-popover {
    width: min(360px, calc(100vw - 24px));
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    justify-content: stretch;
  }

  .workspace-tools-popover > * {
    width: 100%;
    min-width: 0;
    justify-content: center;
  }

  .activity-stage__content {
    padding: var(--space-2);
  }

  .activity-controls {
    min-height: 50px;
    padding: 3px var(--space-2);
  }
}

@media (max-width: 380px) {
  .mode-tab__icon {
    display: none;
  }

  .workspace-tools-toggle {
    min-width: 52px;
  }
}



/* Combined workspace chrome + collapsible desktop topic rail.
   Keep the learning modes in the global top bar so the activity receives the
   vertical space previously occupied by a second workspace header. */
.topbar-workspace-controls {
  grid-area: workspace-controls;
  min-width: 0;
  display: flex;
  align-items: center;
  justify-content: flex-end;
}

.app-shell[data-view="landing"] .topbar-workspace-controls {
  display: none;
}

.app-shell[data-view="workspace"] .topbar__status {
  display: none;
}

.app-shell[data-view="workspace"] .app-shell__topbar {
  grid-template-areas: "brand context workspace-controls";
  grid-template-columns: minmax(150px, 0.65fr) minmax(220px, 0.95fr) minmax(500px, 2fr);
  gap: var(--space-3);
}

.topbar-workspace-controls .workspace-header__controls {
  width: 100%;
  flex: 1 1 auto;
}

.topbar-workspace-controls .mode-tabs {
  width: min(100%, 520px);
}

.app-shell[data-view="workspace"] .workspace-header {
  display: none;
}

.topic-navigation__collapse {
  width: 32px;
  height: 32px;
  display: grid;
  place-items: center;
  flex: 0 0 auto;
  padding: 0;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-secondary);
  cursor: pointer;
}

.topic-navigation__collapse:hover,
.topic-navigation__collapse:focus-visible {
  border-color: var(--mode-accent);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  outline: none;
}

.topic-navigation__collapse-icon {
  font-size: 1.35rem;
  line-height: 1;
  transform: translateY(-1px);
}

@media (min-width: 901px) {
  .app-shell__body {
    transition: grid-template-columns var(--motion-normal) var(--motion-easing);
  }

  .topic-navigation {
    transition:
      width var(--motion-normal) var(--motion-easing),
      padding var(--motion-normal) var(--motion-easing);
  }

  .app-shell[data-sidebar-collapsed="true"] .app-shell__body {
    grid-template-columns: 48px minmax(0, 1fr);
  }

  .app-shell[data-sidebar-collapsed="true"] .topic-navigation {
    width: 48px;
    padding: 6px;
    overflow: hidden;
  }

  .app-shell[data-sidebar-collapsed="true"] .topic-navigation__heading-row {
    min-height: 36px;
    justify-content: center;
  }

  .app-shell[data-sidebar-collapsed="true"] .topic-navigation__heading,
  .app-shell[data-sidebar-collapsed="true"] .topic-navigation__section,
  .app-shell[data-sidebar-collapsed="true"] .topic-navigation__checkpoint,
  .app-shell[data-sidebar-collapsed="true"] .topic-navigation__full-course,
  .app-shell[data-sidebar-collapsed="true"] .data-management-trigger {
    display: none;
  }

  .app-shell[data-sidebar-collapsed="true"] .topic-navigation__actions {
    width: 100%;
    justify-content: center;
  }
}

@media (max-width: 1180px) and (min-width: 901px) {
  .app-shell[data-view="workspace"] .app-shell__topbar {
    grid-template-columns: minmax(120px, 0.5fr) minmax(170px, 0.7fr) minmax(440px, 2fr);
  }

  .app-shell[data-view="workspace"] .breadcrumb {
    font-size: var(--text-sm);
  }

  .app-shell[data-view="workspace"] .scope-badge {
    padding-inline: var(--space-2);
    font-size: 0.64rem;
  }
}

@media (max-width: 900px) {
  .topic-navigation__collapse {
    display: none;
  }

  .app-shell[data-view="workspace"] .app-shell__topbar {
    grid-template-areas:
      "brand nav-toggle context"
      "workspace-controls workspace-controls workspace-controls";
    grid-template-columns: auto auto minmax(0, 1fr);
    row-gap: var(--space-2);
  }

  .topbar-workspace-controls {
    width: 100%;
  }

  .topbar-workspace-controls .workspace-header__controls {
    justify-content: stretch;
  }

  .topbar-workspace-controls .mode-tabs {
    flex: 1 1 auto;
    max-width: none;
  }
}

@media (max-width: 680px) {
  .app-shell[data-view="workspace"] .app-shell__topbar {
    grid-template-areas:
      "brand nav-toggle"
      "context context"
      "workspace-controls workspace-controls";
    grid-template-columns: minmax(0, 1fr) auto;
  }

  .topbar-workspace-controls .workspace-header__controls {
    gap: 4px;
  }

  .topbar-workspace-controls .workspace-tools-toggle {
    min-width: 54px;
  }
}


/* Edge activity navigation: retain Previous/Next behaviour without spending a
   permanent row of vertical workspace. The controls sit on the learning-panel
   edges and stay deliberately quiet until hover/focus. */
.app-shell[data-view="workspace"] .learning-workspace {
  position: relative;
  grid-template-rows: minmax(0, 1fr);
}

.app-shell[data-view="workspace"] .activity-edge-navigation {
  position: absolute;
  inset: 0;
  z-index: 12;
  min-height: 0;
  display: block;
  padding: 0;
  border: 0;
  background: transparent;
  pointer-events: none;
}

.app-shell[data-view="workspace"] .activity-edge-navigation__button {
  position: absolute;
  top: 50%;
  width: 38px;
  height: 56px;
  min-width: 0;
  min-height: 0;
  display: grid;
  place-items: center;
  padding: 0;
  border: 1px solid color-mix(in srgb, var(--border-default) 72%, transparent);
  border-radius: var(--radius-pill);
  background: color-mix(in srgb, var(--surface-base) 86%, transparent);
  color: var(--text-secondary);
  box-shadow: 0 2px 10px color-mix(in srgb, var(--text-primary) 8%, transparent);
  opacity: 0.42;
  pointer-events: auto;
  transform: translateY(-50%);
  transition:
    opacity var(--motion-fast) var(--motion-easing),
    background-color var(--motion-fast) var(--motion-easing),
    border-color var(--motion-fast) var(--motion-easing),
    color var(--motion-fast) var(--motion-easing),
    transform var(--motion-fast) var(--motion-easing);
}

.app-shell[data-view="workspace"] .activity-edge-navigation__button--previous {
  left: 6px;
}

.app-shell[data-view="workspace"] .activity-edge-navigation__button--next {
  right: 6px;
}

.app-shell[data-view="workspace"] .activity-edge-navigation__button:hover,
.app-shell[data-view="workspace"] .activity-edge-navigation__button:focus-visible {
  border-color: var(--mode-accent);
  background: color-mix(in srgb, var(--mode-soft) 92%, var(--surface-base));
  color: var(--mode-soft-text);
  opacity: 0.96;
  outline: none;
  transform: translateY(-50%) scale(1.04);
}

.app-shell[data-view="workspace"] .activity-edge-navigation__button:focus-visible {
  box-shadow:
    0 0 0 3px color-mix(in srgb, var(--mode-accent) 22%, transparent),
    0 2px 10px color-mix(in srgb, var(--text-primary) 10%, transparent);
}

.app-shell[data-view="workspace"] .activity-edge-navigation__button:disabled {
  visibility: hidden;
  opacity: 0;
  pointer-events: none;
}

.activity-edge-navigation__icon {
  display: block;
  font-size: 2rem;
  font-weight: var(--weight-medium);
  line-height: 1;
  transform: translateY(-1px);
}

.app-shell[data-view="workspace"] .activity-edge-navigation__button::after {
  position: absolute;
  top: 50%;
  z-index: 2;
  width: max-content;
  max-width: 150px;
  padding: 5px 8px;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background: var(--surface-raised);
  color: var(--text-secondary);
  box-shadow: var(--shadow-raised);
  content: attr(aria-label);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  line-height: 1;
  opacity: 0;
  pointer-events: none;
  transform: translateY(-50%);
  transition: opacity var(--motion-fast) var(--motion-easing);
  white-space: nowrap;
}

.app-shell[data-view="workspace"] .activity-edge-navigation__button--previous::after {
  left: calc(100% + 7px);
}

.app-shell[data-view="workspace"] .activity-edge-navigation__button--next::after {
  right: calc(100% + 7px);
}

.app-shell[data-view="workspace"] .activity-edge-navigation__button:hover::after,
.app-shell[data-view="workspace"] .activity-edge-navigation__button:focus-visible::after {
  opacity: 1;
}

@media (max-width: 680px) {
  .app-shell[data-view="workspace"] .activity-edge-navigation__button {
    width: 32px;
    height: 48px;
    opacity: 0.34;
  }

  .app-shell[data-view="workspace"] .activity-edge-navigation__button--previous {
    left: 2px;
  }

  .app-shell[data-view="workspace"] .activity-edge-navigation__button--next {
    right: 2px;
  }

  .activity-edge-navigation__icon {
    font-size: 1.7rem;
  }

  .app-shell[data-view="workspace"] .activity-edge-navigation__button::after {
    display: none;
  }
}

@media (prefers-reduced-motion: reduce) {
  .app-shell[data-view="workspace"] .activity-edge-navigation__button {
    transition: none;
  }
}


/* Understand title deduplication 2026-10-05.
   Every Understand page should present one visible title. Standard pages keep
   the activity h2 and drop its overline; bespoke visual pages keep their own
   contextual heading and drop the duplicate teaching-column title as well. */
html[data-learning-mode="understand"] .activity-copy > .activity-overline {
  display: none;
}

.activity-stage__content[data-custom-understand-active="true"] > .activity-copy > h2 {
  display: none;
}

.activity-stage__content[data-custom-understand-active="true"] .understand-visual-host [class$="__eyebrow"] {
  display: none;
}

/* With the duplicate heading removed, the teaching column begins directly
   with explanation/support copy rather than leaving title-sized whitespace. */
.activity-stage__content[data-custom-understand-active="true"] > .activity-copy > p[data-activity-body]:first-of-type,
.activity-stage__content[data-custom-understand-active="true"] > .activity-copy > .activity-callout:first-child {
  margin-top: 0;
}


/* Dismissible instruction pop-ins for bespoke Understand experiences.
   Instructions are centred over the activity on first view. Once dismissed,
   Review instructions lives in the shared workspace bar so it never obscures
   the activity title or steals diagram space. */
.activity-stage__content[data-custom-understand-active="true"] {
  position: relative;
  grid-template-columns: minmax(0, 1fr) !important;
  align-items: stretch;
  min-width: 0;
  min-height: 100%;
}

.activity-stage__content[data-custom-understand-active="true"]::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 22;
  display: none;
  border-radius: inherit;
  background: color-mix(in srgb, var(--surface-canvas) 48%, transparent);
  backdrop-filter: blur(1.5px);
}

.activity-stage__content[data-custom-understand-active="true"][data-understand-instructions-open="true"]::after {
  display: block;
}

.activity-stage__content[data-custom-understand-active="true"] > .activity-copy {
  position: fixed !important;
  top: 50%;
  left: 50%;
  z-index: 40;
  width: min(540px, calc(100% - 48px));
  max-width: calc(100% - 48px);
  max-height: min(72dvh, calc(100% - 48px)) !important;
  overflow: auto !important;
  padding: var(--space-5);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-xl);
  background: var(--surface-base);
  box-shadow: var(--shadow-drawer);
  transform: translate(-50%, -50%);
}

.activity-stage__content[data-custom-understand-active="true"] > .activity-copy[hidden],
.understand-instructions-popin__header[hidden],
.understand-instructions-review[hidden] {
  display: none !important;
}

.activity-stage__content[data-custom-understand-active="true"] > .math-placeholder {
  grid-column: 1 !important;
  width: 100%;
  min-width: 0;
  min-height: 0;
}

/* Do not let the instruction layer participate in layout sizing. The visual
   keeps the full width/height it had after the pop-in is closed. */
.activity-stage__content[data-custom-understand-active="true"] > .math-placeholder,
.activity-stage__content[data-custom-understand-active="true"] .understand-visual-host {
  max-width: 100%;
}

.understand-instructions-popin__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  margin-bottom: var(--space-3);
  padding-bottom: var(--space-3);
  border-bottom: 1px solid var(--divider-default);
}

.understand-instructions-popin__header strong {
  color: var(--text-primary);
  font-size: var(--text-sm);
  letter-spacing: .02em;
}

.understand-instructions-popin__close {
  width: 36px;
  height: 36px;
  flex: 0 0 auto;
  display: grid;
  place-items: center;
  padding: 0;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-subtle);
  color: var(--text-secondary);
  font: inherit;
  font-size: 1.35rem;
  line-height: 1;
  cursor: pointer;
}

.understand-instructions-popin__close:hover,
.understand-instructions-popin__close:focus-visible {
  border-color: var(--mode-accent);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  outline: none;
}

.activity-stage__content[data-custom-understand-active="true"] > .activity-copy > p[data-activity-body] {
  margin: 0;
  color: var(--text-secondary);
  font-size: var(--text-base);
  line-height: var(--leading-relaxed);
}

.activity-stage__content[data-custom-understand-active="true"] > .activity-copy > .activity-callout {
  margin-top: var(--space-4);
}

/* Review is now part of the same chrome as the learning-mode and Tools
   controls. It is intentionally quieter than the mode tabs. */
.topbar-workspace-controls .understand-instructions-review {
  position: static;
  z-index: auto;
  min-height: var(--touch-target-min);
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  padding: 0 var(--space-3);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-pill);
  background: var(--surface-base);
  color: var(--text-secondary);
  box-shadow: none;
  font: inherit;
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  cursor: pointer;
  white-space: nowrap;
}

.topbar-workspace-controls .understand-instructions-review:hover,
.topbar-workspace-controls .understand-instructions-review:focus-visible {
  border-color: var(--mode-accent);
  background: var(--mode-soft);
  color: var(--mode-soft-text);
  outline: none;
}

.topbar-workspace-controls .understand-instructions-review > span:first-child {
  width: 20px;
  height: 20px;
  display: inline-grid;
  place-items: center;
  border-radius: var(--radius-pill);
  background: var(--surface-subtle);
  font-weight: var(--weight-bold);
}

@media (max-width: 1400px) {
  .topbar-workspace-controls .understand-instructions-review {
    width: var(--touch-target-min);
    min-width: var(--touch-target-min);
    padding: 0;
  }

  .topbar-workspace-controls .understand-instructions-review > span:last-child {
    display: none;
  }
}

@media (max-width: 680px) {
  .activity-stage__content[data-custom-understand-active="true"] > .activity-copy {
    width: calc(100% - 24px);
    max-width: calc(100% - 24px);
    max-height: min(74dvh, calc(100% - 24px)) !important;
    padding: var(--space-4);
  }
}

@media (prefers-reduced-motion: no-preference) {
  .activity-stage__content[data-custom-understand-active="true"] > .activity-copy {
    animation: understand-instructions-enter 140ms var(--motion-easing);
  }
}

@keyframes understand-instructions-enter {
  from {
    opacity: 0;
    transform: translate(-50%, calc(-50% + 8px)) scale(.985);
  }
  to {
    opacity: 1;
    transform: translate(-50%, -50%) scale(1);
  }
}



/* Understand visual sizing audit 2026-10-06.
   Custom Understand activities should fit the available teaching viewport after
   the chrome/side-bar changes. Wide diagrams no longer derive an excessive
   height purely from their width; dense activities scroll inside their visual
   surface rather than extending below the browser. */
.activity-stage__content[data-custom-understand-active="true"] {
  --understand-graph-height: clamp(240px, 48dvh, 500px);
  height: 100%;
  min-height: 0;
  overflow: hidden;
}

html[data-ui-density="compact"] .activity-stage__content[data-custom-understand-active="true"] {
  --understand-graph-height: clamp(220px, 43dvh, 430px);
}

html[data-ui-density="tight"] .activity-stage__content[data-custom-understand-active="true"] {
  --understand-graph-height: clamp(200px, 38dvh, 370px);
}

.activity-stage__content[data-custom-understand-active="true"] > .math-placeholder {
  height: 100% !important;
  max-height: 100% !important;
  min-height: 0 !important;
  overflow: hidden !important;
}

.activity-stage__content[data-custom-understand-active="true"] .understand-visual-host {
  height: 100%;
  max-height: 100%;
  min-height: 0;
  overflow: auto;
  overscroll-behavior: contain;
}

.activity-stage__content[data-custom-understand-active="true"] .understand-visual-host > * {
  height: auto !important;
  max-height: 100% !important;
  min-height: 0 !important;
  overflow: auto !important;
}

/* Shared graph renderer: preserve the SVG's own viewBox proportions inside a
   viewport-aware box instead of letting the CSS aspect ratio make a full-width
   graph taller than the screen. */
.activity-stage__content[data-custom-understand-active="true"] .diagram-primitives {
  height: var(--understand-graph-height) !important;
  min-height: 0 !important;
  max-height: var(--understand-graph-height) !important;
  aspect-ratio: auto !important;
}

.activity-stage__content[data-custom-understand-active="true"] .diagram-primitives__svg {
  min-height: 0 !important;
  max-height: 100% !important;
}

/* Older topic-specific layouts carried desktop min-heights from the previous
   two-column shell. Those values are now allowed to shrink with the workspace. */
.activity-stage__content[data-custom-understand-active="true"] :is(
  .pre-calculus-understand__graph-host,
  .first-principles-understand__graph-host,
  .trig-identities-inverse-understand__graph,
  .concavity-inflection-understand__graph,
  .limit-of-sum-understand__explorer,
  .differential-equations-understand__family,
  .trapezium-integration-understand__builder
) {
  min-height: 0 !important;
  max-height: 100%;
}

/* Graph-heavy shared explorers should consume the remaining visual space, not
   create a second vertical page inside an activity. */
.activity-stage__content[data-custom-understand-active="true"] :is(
  .linked-gradient-explorer,
  .family-curves-explorer,
  .chord-tangent-explorer,
  .area-explorer,
  .rectangle-sum-explorer,
  .parametric-tracer,
  .rate-flow,
  .trapezium-rule-builder
) {
  max-height: 100%;
}

@media (max-width: 680px) {
  .activity-stage__content[data-custom-understand-active="true"] {
    --understand-graph-height: clamp(200px, 38dvh, 320px);
    height: auto;
    min-height: 0;
    overflow: visible;
  }

  .activity-stage__content[data-custom-understand-active="true"] > .math-placeholder,
  .activity-stage__content[data-custom-understand-active="true"] .understand-visual-host,
  .activity-stage__content[data-custom-understand-active="true"] .understand-visual-host > * {
    height: auto !important;
    max-height: none !important;
    overflow: visible !important;
  }
}