:root {
  color-scheme: light dark;

  --bg-page: #ffffff;
  --bg-surface: #f4f6f8;
  --bg-card: #f8fafc;
  --bg-elevated: #ffffff;
  --bg-hover: #eef2f5;
  --svg-card: #ffffff;

  --text-main: #1a202c;
  --text-sub: #4b5563;
  --text-muted: #718096;

  --border-subtle: #e2e8f0;
  --border-strong: #cbd5e1;

  --accent-green: #00b37e;
  --accent-green-hover: #009c6e;
  --accent-green-soft: rgba(0, 179, 126, 0.13);
  --accent-green-hl: rgba(0, 179, 126, 0.24);

  --accent-check: #5c5ce6;
  --accent-exercise: #c73882;
  --accent-std: #2563eb;
  --accent-std-soft: rgba(37, 99, 235, 0.12);
  --accent-adv: #d97706;
  --accent-adv-soft: rgba(217, 119, 6, 0.14);

  --ok-bg: rgba(0, 179, 126, 0.12);
  --ok-border: #00b37e;
  --ok-text: #046c4e;

  --ng-bg: rgba(229, 62, 62, 0.1);
  --ng-border: #e53e3e;
  --ng-text: #9b1c1c;

  --shadow-card: 0 2px 10px rgba(15, 23, 42, 0.04);
  --shadow-footer: 0 -4px 16px rgba(15, 23, 42, 0.06);
  --font-sans: "Hiragino Kaku Gothic ProN", "Hiragino Sans", "Yu Gothic UI", "Meiryo", system-ui, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg-page: #11161d;
    --bg-surface: #1b222c;
    --bg-card: #18202a;
    --bg-elevated: #1e2631;
    --bg-hover: #242e3b;
    --svg-card: #1b222c;

    --text-main: #edf2f7;
    --text-sub: #a9b4c4;
    --text-muted: #7c8899;

    --border-subtle: #2b3544;
    --border-strong: #3d4a5e;

    --accent-green: #14c992;
    --accent-green-hover: #10b07f;
    --accent-green-soft: rgba(20, 201, 146, 0.18);
    --accent-green-hl: rgba(20, 201, 146, 0.28);

    --accent-std: #60a5fa;
    --accent-std-soft: rgba(96, 165, 250, 0.16);
    --accent-adv: #fbbf24;
    --accent-adv-soft: rgba(251, 191, 36, 0.16);

    --ok-bg: rgba(20, 201, 146, 0.16);
    --ok-text: #6ee7b7;
    --ng-bg: rgba(245, 101, 101, 0.16);
    --ng-text: #feb2b2;

    --shadow-card: 0 2px 12px rgba(0, 0, 0, 0.25);
    --shadow-footer: 0 -4px 18px rgba(0, 0, 0, 0.35);
  }
}

:root:has(> head > meta[name="color-scheme"][content="light"]) {
  --bg-page: #ffffff;
  --bg-surface: #f4f6f8;
  --bg-card: #f8fafc;
  --bg-elevated: #ffffff;
  --bg-hover: #eef2f5;
  --svg-card: #ffffff;
  --text-main: #1a202c;
  --text-sub: #4b5563;
  --text-muted: #718096;
  --border-subtle: #e2e8f0;
  --border-strong: #cbd5e1;
  --accent-green: #00b37e;
  --accent-green-hover: #009c6e;
  --accent-green-soft: rgba(0, 179, 126, 0.13);
  --accent-green-hl: rgba(0, 179, 126, 0.24);
  --accent-std: #2563eb;
  --accent-std-soft: rgba(37, 99, 235, 0.12);
  --accent-adv: #d97706;
  --accent-adv-soft: rgba(217, 119, 6, 0.14);
  --ok-bg: rgba(0, 179, 126, 0.12);
  --ok-text: #046c4e;
  --ng-bg: rgba(229, 62, 62, 0.1);
  --ng-text: #9b1c1c;
  --shadow-card: 0 2px 10px rgba(15, 23, 42, 0.04);
  --shadow-footer: 0 -4px 16px rgba(15, 23, 42, 0.06);
}

:root:has(> head > meta[name="color-scheme"][content="dark"]) {
  --bg-page: #11161d;
  --bg-surface: #1b222c;
  --bg-card: #18202a;
  --bg-elevated: #1e2631;
  --bg-hover: #242e3b;
  --svg-card: #1b222c;
  --text-main: #edf2f7;
  --text-sub: #a9b4c4;
  --text-muted: #7c8899;
  --border-subtle: #2b3544;
  --border-strong: #3d4a5e;
  --accent-green: #14c992;
  --accent-green-hover: #10b07f;
  --accent-green-soft: rgba(20, 201, 146, 0.18);
  --accent-green-hl: rgba(20, 201, 146, 0.28);
  --accent-std: #60a5fa;
  --accent-std-soft: rgba(96, 165, 250, 0.16);
  --accent-adv: #fbbf24;
  --accent-adv-soft: rgba(251, 191, 36, 0.16);
  --ok-bg: rgba(20, 201, 146, 0.16);
  --ok-text: #6ee7b7;
  --ng-bg: rgba(245, 101, 101, 0.16);
  --ng-text: #feb2b2;
  --shadow-card: 0 2px 12px rgba(0, 0, 0, 0.25);
  --shadow-footer: 0 -4px 18px rgba(0, 0, 0, 0.35);
}

*, *::before, *::after {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg-surface);
  color: var(--text-main);
  font-family: var(--font-sans);
  -webkit-font-smoothing: antialiased;
}

button, select {
  font: inherit;
  color: inherit;
}

.is-hidden {
  display: none !important;
}

/* =========================================================================
   App Shell & Views
   ========================================================================= */
.app-shell {
  min-height: 100dvh;
  max-width: 740px;
  margin: 0 auto;
  background: var(--bg-page);
  display: flex;
  flex-direction: column;
}

.view {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
}

.app-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: var(--bg-page);
  padding: calc(10px + env(safe-area-inset-top)) 16px 12px;
  border-bottom: 1px solid var(--border-subtle);
}

.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 38px;
  min-height: 38px;
  padding: 6px;
  border: 0;
  border-radius: 10px;
  background: transparent;
  color: var(--text-sub);
  cursor: pointer;
  transition: background-color 0.15s ease, color 0.15s ease;
}

.icon-btn:hover {
  background: var(--bg-surface);
  color: var(--text-main);
}

.icon-btn[aria-pressed="true"] {
  color: var(--accent-adv);
  background: var(--accent-adv-soft);
}

.icon-btn[aria-pressed="true"] svg path {
  fill: currentColor;
}

.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  min-height: 36px;
  padding: 4px 10px 4px 6px;
  border: 1px solid var(--border-subtle);
  border-radius: 9px;
  background: var(--bg-surface);
  color: var(--text-main);
  font-size: 0.84rem;
  font-weight: 700;
  cursor: pointer;
}

.back-btn:hover {
  background: var(--bg-hover);
}

.back-btn.is-compact {
  padding: 4px 8px 4px 4px;
  font-size: 0.8rem;
}

/* =========================================================================
   1. Home View (Chapter -> Small Units)
   ========================================================================= */
.home-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 10px;
}

.subject-kicker {
  margin: 0;
  font-size: 0.74rem;
  font-weight: 700;
  color: var(--accent-green);
}

.home-title {
  margin: 2px 0 0;
  font-size: 1.25rem;
  font-weight: 800;
  line-height: 1.3;
}

.overall-card {
  margin-top: 10px;
  padding: 10px 12px;
  border-radius: 12px;
  background: var(--bg-surface);
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.overall-top {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--text-sub);
}

.overall-pct {
  font-size: 1rem;
  font-weight: 800;
  color: var(--accent-green);
}

.bar-track {
  width: 100%;
  height: 7px;
  border-radius: 999px;
  background: var(--border-subtle);
  overflow: hidden;
}

.bar-fill {
  height: 100%;
  border-radius: 999px;
  background: var(--accent-green);
  transition: width 0.25s ease;
}

.filter-panel {
  margin-top: 10px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.filter-block {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
}

.filter-label {
  font-size: 0.74rem;
  font-weight: 700;
  color: var(--text-muted);
  margin-right: 2px;
}

.pill-row {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
}

.course-pill,
.filter-pill,
.preset-btn {
  min-height: 30px;
  padding: 3px 10px;
  border-radius: 999px;
  border: 1.5px solid var(--border-subtle);
  background: var(--bg-elevated);
  color: var(--text-sub);
  font-size: 0.75rem;
  font-weight: 700;
  cursor: pointer;
  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

.preset-btn {
  border-radius: 8px;
  background: var(--bg-surface);
}

.preset-btn.is-active {
  background: var(--accent-green-soft);
  border-color: var(--accent-green);
  color: var(--accent-green);
}

.course-pill[aria-pressed="true"][data-level="essential"] {
  background: var(--accent-green-soft);
  border-color: var(--accent-green);
  color: var(--accent-green);
}

.course-pill[aria-pressed="true"][data-level="standard"] {
  background: var(--accent-std-soft);
  border-color: var(--accent-std);
  color: var(--accent-std);
}

.course-pill[aria-pressed="true"][data-level="advanced"] {
  background: var(--accent-adv-soft);
  border-color: var(--accent-adv);
  color: var(--accent-adv);
}

.filter-pill.is-active {
  background: var(--accent-green-soft);
  border-color: var(--accent-green);
  color: var(--accent-green);
}

.home-main {
  flex: 1;
  padding: 14px 16px calc(28px + env(safe-area-inset-bottom));
  background: var(--bg-surface);
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.chapter-card {
  background: var(--bg-page);
  border: 1px solid var(--border-subtle);
  border-radius: 16px;
  padding: 14px;
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.chapter-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.chapter-title {
  margin: 0;
  font-size: 1.02rem;
  font-weight: 800;
  line-height: 1.35;
}

.chapter-meta {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--text-muted);
  margin-top: 2px;
}

.chapter-pct {
  font-size: 0.96rem;
  font-weight: 800;
  color: var(--text-main);
  flex-shrink: 0;
}

.subunits-stack {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.subunit-btn {
  width: 100%;
  text-align: left;
  padding: 11px 12px;
  border-radius: 12px;
  border: 1px solid var(--border-subtle);
  background: var(--bg-card);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  gap: 6px;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.subunit-btn:hover {
  border-color: var(--accent-green);
  background: var(--bg-hover);
}

.subunit-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.subunit-name {
  font-size: 0.94rem;
  font-weight: 700;
  line-height: 1.35;
  color: var(--text-main);
}

.subunit-pct {
  font-size: 0.8rem;
  font-weight: 800;
  color: var(--accent-green);
  flex-shrink: 0;
}

.subunit-sub {
  font-size: 0.78rem;
  color: var(--text-sub);
  line-height: 1.4;
}

.subunit-bar-seg {
  display: flex;
  gap: 3px;
}

.subunit-bar-seg span {
  flex: 1;
  height: 5px;
  border-radius: 999px;
  background: var(--border-subtle);
}

.subunit-bar-seg span.is-done {
  background: var(--accent-green);
}

.subunit-bar-seg span.is-review {
  background: var(--accent-adv);
}

/* =========================================================================
   2. Unit Overview View (Inside Small Unit)
   ========================================================================= */
.unit-header-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.unit-pct {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--accent-green);
}

.unit-kicker {
  margin: 8px 0 0;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--accent-green);
}

.unit-title {
  margin: 2px 0 0;
  font-size: 1.2rem;
  font-weight: 800;
  line-height: 1.35;
}

.unit-subtitle {
  margin: 4px 0 0;
  font-size: 0.85rem;
  color: var(--text-sub);
  line-height: 1.5;
}

.unit-breakdown {
  margin-top: 10px;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
}

.bd-item {
  background: var(--bg-surface);
  border-radius: 10px;
  padding: 7px 9px;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.bd-head {
  display: flex;
  justify-content: space-between;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--text-sub);
}

.bd-bar {
  height: 4px;
  border-radius: 999px;
  background: var(--border-subtle);
  overflow: hidden;
}

.bd-bar > i {
  display: block;
  height: 100%;
  border-radius: 999px;
  background: var(--accent-green);
}

.bd-item[data-cat="check"] .bd-bar > i {
  background: var(--accent-check);
}

.bd-item[data-cat="exercise"] .bd-bar > i {
  background: var(--accent-exercise);
}

.unit-main {
  flex: 1;
  padding: 14px 16px calc(28px + env(safe-area-inset-bottom));
  background: var(--bg-surface);
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.btn-primary-full {
  width: 100%;
  min-height: 48px;
  border: 0;
  border-radius: 12px;
  background: var(--accent-green);
  color: #fff;
  font-size: 0.98rem;
  font-weight: 800;
  cursor: pointer;
  box-shadow: 0 4px 12px rgba(0, 179, 126, 0.22);
}

.btn-primary-full:hover {
  background: var(--accent-green-hover);
}

.unit-step-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.unit-step-card {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 11px;
  padding: 12px;
  border-radius: 13px;
  border: 1px solid var(--border-subtle);
  background: var(--bg-page);
  text-align: left;
  cursor: pointer;
  box-shadow: var(--shadow-card);
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.unit-step-card:hover {
  border-color: var(--accent-green);
  background: var(--bg-hover);
}

.unit-step-icon {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  background: var(--accent-green);
  flex-shrink: 0;
}

.unit-step-icon[data-type="check"] {
  background: var(--accent-check);
}

.unit-step-icon[data-type="exercise"] {
  background: var(--accent-exercise);
}

.unit-step-body {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.unit-step-title {
  font-size: 0.92rem;
  font-weight: 700;
  color: var(--text-main);
  line-height: 1.35;
}

.unit-step-tags {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
}

.unit-step-type {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--text-muted);
}

.status-pill {
  font-size: 0.7rem;
  font-weight: 800;
  padding: 3px 8px;
  border-radius: 999px;
  background: var(--bg-surface);
  color: var(--text-muted);
  flex-shrink: 0;
}

.status-pill.is-done {
  background: var(--ok-bg);
  color: var(--ok-text);
}

.status-pill.is-review {
  background: var(--accent-adv-soft);
  color: var(--accent-adv);
}

.unit-reset-row {
  margin-top: 6px;
}

/* =========================================================================
   3. Lesson Player View
   ========================================================================= */
.header-top {
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 8px;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 6px;
}

.step-badge {
  width: 32px;
  height: 32px;
  border-radius: 9px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  background: var(--accent-green);
  flex-shrink: 0;
}

.step-badge[data-type="check"] {
  background: var(--accent-check);
}

.step-badge[data-type="exercise"] {
  background: var(--accent-exercise);
}

.header-title {
  margin: 0;
  font-size: 0.96rem;
  font-weight: 700;
  text-align: center;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.header-actions {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 2px;
}

.progress-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 8px;
}

.progress-label {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--text-muted);
  white-space: nowrap;
}

.progress-segments {
  flex: 1;
  display: flex;
  align-items: center;
  gap: 3px;
  min-width: 0;
}

.progress-seg {
  flex: 1;
  height: 4px;
  border-radius: 999px;
  background: var(--border-subtle);
  transition: background-color 0.2s ease, transform 0.2s ease;
}

.progress-seg.is-done {
  background: var(--accent-green);
}

.progress-seg.is-current {
  background: var(--accent-green);
  transform: scaleY(1.45);
}

.progress-count {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--text-sub);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

.stage {
  flex: 1;
  padding: 18px 16px 32px;
  overflow-wrap: anywhere;
}

.stage-inner {
  display: flex;
  flex-direction: column;
  gap: 15px;
}

.step-meta-row {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.level-badge {
  display: inline-flex;
  align-items: center;
  padding: 2px 9px;
  border-radius: 999px;
  font-size: 0.72rem;
  font-weight: 800;
}

.level-badge[data-level="essential"] {
  background: var(--accent-green-soft);
  color: var(--accent-green);
}

.level-badge[data-level="standard"] {
  background: var(--accent-std-soft);
  color: var(--accent-std);
}

.level-badge[data-level="advanced"] {
  background: var(--accent-adv-soft);
  color: var(--accent-adv);
}

.topic-chip {
  font-size: 0.74rem;
  font-weight: 600;
  color: var(--text-muted);
}

.tb-heading {
  margin: 0 0 2px;
  padding-left: 12px;
  border-left: 4px solid var(--accent-green);
  font-size: 1.18rem;
  font-weight: 800;
  line-height: 1.45;
  text-wrap: balance;
}

.stage-inner p,
.stage-inner li {
  margin: 0;
  font-size: 0.98rem;
  line-height: 1.82;
  text-wrap: pretty;
}

.hl-mint {
  background: linear-gradient(transparent 58%, var(--accent-green-hl) 58%);
  font-weight: 700;
  padding: 0 2px;
  border-radius: 2px;
}

/* Unified content boxes (also alias legacy class names cleanly) */
.formula-box,
.math-box {
  background: var(--bg-surface);
  border-radius: 12px;
  padding: 12px 14px;
  overflow-x: auto;
  text-align: center;
}

.formula-box .katex-display,
.math-box .katex-display {
  margin: 0.25em 0;
}

.info-card,
.callout-card,
.highlight-box {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: 12px;
  padding: 13px 15px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.highlight-box {
  border-left: 4px solid var(--accent-green);
  background: var(--accent-green-soft);
}

.callout-title,
.highlight-title {
  font-size: 0.9rem;
  font-weight: 800;
  color: var(--text-main);
}

.clean-list {
  margin: 0;
  padding-left: 1.25em;
  display: flex;
  flex-direction: column;
  gap: 7px;
}

.diagram-box,
.diagram-card {
  margin: 4px 0;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: 14px;
  padding: 12px;
}

.diagram-box figcaption,
.diagram-card figcaption {
  margin-top: 8px;
  font-size: 0.82rem;
  line-height: 1.5;
  color: var(--text-sub);
  text-align: center;
}

/* Inline Example Box inside Textbook Steps */
.example-box {
  border: 1.5px solid var(--border-strong);
  border-radius: 14px;
  background: var(--bg-elevated);
  padding: 14px 15px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.example-head {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.94rem;
  font-weight: 800;
  color: var(--text-main);
}

.example-badge {
  font-size: 0.7rem;
  font-weight: 800;
  padding: 2px 8px;
  border-radius: 6px;
  background: var(--accent-green);
  color: #fff;
}

.example-prompt-note {
  padding: 10px 12px;
  border-radius: 10px;
  background: var(--bg-surface);
  font-size: 0.84rem;
  color: var(--text-sub);
}

.example-toggle-btn {
  width: 100%;
  min-height: 42px;
  border-radius: 10px;
  border: 1.5px solid var(--accent-green);
  background: var(--accent-green-soft);
  color: var(--accent-green);
  font-size: 0.88rem;
  font-weight: 800;
  cursor: pointer;
}

.example-toggle-btn:hover {
  background: var(--accent-green);
  color: #fff;
}

.example-answer {
  padding-top: 10px;
  border-top: 1px dashed var(--border-strong);
  display: flex;
  flex-direction: column;
  gap: 8px;
}

/* =========================================================================
   Basic Check & Exercise UI
   ========================================================================= */
.check-prompt {
  font-size: 1.02rem;
  line-height: 2.05;
  padding: 4px 0 8px;
}

.blank-chip {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 72px;
  min-height: 34px;
  padding: 2px 12px;
  margin: 2px 4px;
  border-radius: 8px;
  border: 1.5px dashed var(--border-strong);
  background: var(--bg-page);
  color: var(--text-muted);
  font-size: 0.92rem;
  font-weight: 700;
  vertical-align: middle;
  cursor: pointer;
}

.blank-chip.is-active {
  border-style: solid;
  border-width: 2px;
  border-color: var(--accent-green);
  background: var(--accent-green-soft);
  color: var(--accent-green);
}

.blank-chip.is-filled {
  border-style: solid;
  border-color: var(--border-strong);
  background: var(--bg-surface);
  color: var(--text-main);
}

.blank-chip.is-correct {
  border-style: solid;
  border-color: var(--ok-border);
  background: var(--ok-bg);
  color: var(--ok-text);
}

.blank-chip.is-wrong {
  border-style: solid;
  border-color: var(--ng-border);
  background: var(--ng-bg);
  color: var(--ng-text);
}

.choice-section-label {
  margin: 4px 0 6px;
  font-size: 0.86rem;
  font-weight: 700;
  color: var(--text-sub);
}

.choice-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
}

.choice-grid.is-single-col {
  grid-template-columns: 1fr;
}

.choice-btn {
  display: flex;
  align-items: center;
  gap: 10px;
  width: 100%;
  min-height: 52px;
  padding: 11px 13px;
  border: 1.5px solid var(--border-subtle);
  border-radius: 12px;
  background: var(--bg-elevated);
  text-align: left;
  cursor: pointer;
}

.choice-btn:hover {
  border-color: var(--border-strong);
  background: var(--bg-hover);
}

.choice-btn.is-selected {
  border-color: var(--accent-green);
  background: var(--accent-green-soft);
}

.choice-btn.is-correct {
  border-color: var(--ok-border);
  background: var(--ok-bg);
}

.choice-btn.is-wrong {
  border-color: var(--ng-border);
  background: var(--ng-bg);
}

.choice-num {
  font-size: 0.84rem;
  font-weight: 700;
  color: var(--text-muted);
  flex-shrink: 0;
}

.choice-text {
  flex: 1;
  font-size: 0.95rem;
  font-weight: 600;
  line-height: 1.55;
  overflow-x: auto;
}

.btn-idk {
  width: 100%;
  min-height: 46px;
  padding: 10px 14px;
  border: 1.5px dashed var(--border-strong);
  border-radius: 12px;
  background: transparent;
  color: var(--text-sub);
  font-size: 0.88rem;
  font-weight: 700;
  cursor: pointer;
}

.btn-idk:hover {
  background: var(--bg-surface);
}

.source-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: -4px;
}

.feedback-card {
  border-radius: 14px;
  padding: 14px 15px;
  border: 1.5px solid var(--border-subtle);
  background: var(--bg-card);
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.feedback-card.is-ok {
  border-color: var(--ok-border);
  background: var(--ok-bg);
}

.feedback-card.is-ng {
  border-color: var(--ng-border);
  background: var(--ng-bg);
}

.feedback-status {
  font-size: 0.96rem;
  font-weight: 800;
}

.feedback-card.is-ok .feedback-status {
  color: var(--ok-text);
}

.feedback-card.is-ng .feedback-status {
  color: var(--ng-text);
}

.feedback-body {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

/* Completion Card */
.complete-card {
  text-align: center;
  padding: 26px 18px;
  border-radius: 16px;
  border: 1.5px solid var(--accent-green);
  background: var(--accent-green-soft);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.complete-card h2 {
  margin: 0;
  font-size: 1.25rem;
}

.complete-actions {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-top: 6px;
}

.btn-secondary {
  width: 100%;
  min-height: 44px;
  border-radius: 12px;
  border: 1.5px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text-main);
  font-size: 0.92rem;
  font-weight: 700;
  cursor: pointer;
}

.btn-secondary:hover {
  background: var(--bg-hover);
}

/* =========================================================================
   Footer
   ========================================================================= */
.app-footer {
  position: sticky;
  bottom: 0;
  z-index: 20;
  background: var(--bg-page);
  border-top: 1px solid var(--border-subtle);
  box-shadow: var(--shadow-footer);
  padding: 9px 16px calc(11px + env(safe-area-inset-bottom));
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
}

.pager-dots {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  border-radius: 999px;
  background: var(--bg-surface);
}

.pager-dot {
  width: 6px;
  height: 6px;
  border-radius: 999px;
  background: var(--border-strong);
  transition: width 0.2s ease, background-color 0.2s ease;
}

.pager-dot.is-current {
  width: 18px;
  background: var(--accent-green);
}

.nav-buttons {
  width: 100%;
  display: grid;
  grid-template-columns: 1fr 1.25fr;
  gap: 10px;
}

.btn-nav {
  min-height: 46px;
  border-radius: 12px;
  border: 0;
  font-size: 0.96rem;
  font-weight: 800;
  cursor: pointer;
}

.btn-prev {
  background: var(--bg-surface);
  color: var(--text-sub);
}

.btn-prev:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn-next {
  background: var(--accent-green);
  color: #fff;
}

.btn-next:hover {
  background: var(--accent-green-hover);
}

/* =========================================================================
   Simple Rock-Solid Modal TOC (<dialog>)
   ========================================================================= */
dialog:modal {
  overscroll-behavior: contain;
}

dialog::backdrop {
  background: rgba(0, 0, 0, 0.45);
  overflow: hidden;
  overscroll-behavior: contain;
}

.modal-dialog {
  width: min(92vw, 440px);
  max-height: 84dvh;
  margin: auto;
  padding: 0;
  border: 1px solid var(--border-subtle);
  border-radius: 18px;
  background: var(--bg-page);
  color: var(--text-main);
  box-shadow: 0 20px 44px rgba(0, 0, 0, 0.28);
}

.modal-sheet {
  display: flex;
  flex-direction: column;
  max-height: 84dvh;
  padding: 16px;
  gap: 12px;
}

.modal-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 8px;
}

.modal-kicker {
  margin: 0;
  font-size: 0.74rem;
  font-weight: 700;
  color: var(--accent-green);
}

.modal-title {
  margin: 2px 0 0;
  font-size: 1.02rem;
  font-weight: 800;
}

.toc-list {
  list-style: none;
  margin: 0;
  padding: 0;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 6px;
  flex: 1;
}

.toc-item-btn {
  width: 100%;
  min-height: 44px;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 10px;
  border-radius: 10px;
  border: 1px solid transparent;
  background: transparent;
  text-align: left;
  cursor: pointer;
}

.toc-item-btn:hover {
  background: var(--bg-surface);
}

.toc-item-btn.is-current {
  background: var(--accent-green-soft);
  border-color: var(--accent-green);
}

.toc-tag {
  font-size: 0.7rem;
  font-weight: 800;
  padding: 2px 7px;
  border-radius: 6px;
  color: #fff;
  background: var(--accent-green);
  flex-shrink: 0;
}

.toc-tag[data-type="check"] {
  background: var(--accent-check);
}

.toc-tag[data-type="exercise"] {
  background: var(--accent-exercise);
}

.toc-level {
  font-size: 0.66rem;
  font-weight: 800;
  padding: 2px 6px;
  border-radius: 999px;
  flex-shrink: 0;
}

.toc-level[data-level="essential"] {
  background: var(--accent-green-soft);
  color: var(--accent-green);
}

.toc-level[data-level="standard"] {
  background: var(--accent-std-soft);
  color: var(--accent-std);
}

.toc-level[data-level="advanced"] {
  background: var(--accent-adv-soft);
  color: var(--accent-adv);
}

.toc-text {
  flex: 1;
  font-size: 0.85rem;
  font-weight: 600;
  line-height: 1.35;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.toc-done {
  font-size: 0.85rem;
  color: var(--accent-green);
  font-weight: 800;
}

.modal-footer {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding-top: 8px;
  border-top: 1px solid var(--border-subtle);
}

.btn-reset {
  width: 100%;
  min-height: 42px;
  border-radius: 10px;
  border: 1px solid var(--border-strong);
  background: transparent;
  color: var(--text-sub);
  font-size: 0.84rem;
  font-weight: 700;
  cursor: pointer;
}

.btn-reset:hover {
  background: var(--ng-bg);
  border-color: var(--ng-border);
  color: var(--ng-text);
}

.empty-state {
  text-align: center;
  padding: 28px 16px;
  border: 1.5px dashed var(--border-strong);
  border-radius: 14px;
  background: var(--bg-page);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

@media (max-width: 440px) {
  .choice-grid {
    grid-template-columns: 1fr;
  }
}

@media (pointer: coarse) {
  .icon-btn,
  .btn-nav,
  .choice-btn,
  .blank-chip,
  .btn-idk,
  .toc-item-btn,
  .btn-reset,
  .btn-secondary,
  .example-toggle-btn {
    min-height: 44px;
  }
}