:root {
  color-scheme: light;
  --ink: #111827;
  --muted: #64748b;
  --line: #dbe2ea;
  --surface: #ffffff;
  --canvas: #eef2f6;
  --navy: #0b1220;
  --teal: #0f766e;
  --teal-bright: #2dd4bf;
  --teal-soft: #e6fffb;
  --amber: #b45309;
  --amber-soft: #fff7ed;
  --danger: #b91c1c;
  --danger-soft: #fef2f2;
  --success: #047857;
  --success-soft: #ecfdf5;
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
    "Microsoft YaHei", sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  min-width: 320px;
  background: var(--canvas);
}

body {
  margin: 0;
  color: var(--ink);
  background:
    radial-gradient(circle at 16% 0%, rgba(45, 212, 191, 0.08), transparent 24rem),
    var(--canvas);
  min-height: 100vh;
}

button,
a {
  font: inherit;
}

button {
  cursor: pointer;
}

button:focus-visible,
a:focus-visible {
  outline: 3px solid rgba(13, 148, 136, 0.35);
  outline-offset: 2px;
}

.topbar {
  min-height: 78px;
  padding: 0 28px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  color: #f8fafc;
  background: var(--navy);
  border-bottom: 3px solid var(--teal-bright);
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  color: inherit;
  text-decoration: none;
}

.brand-mark {
  width: 42px;
  height: 42px;
  display: grid;
  place-items: center;
  border-radius: 11px;
  color: var(--navy);
  background: var(--teal-bright);
  font-weight: 900;
  font-size: 1.35rem;
}

.brand strong,
.brand small {
  display: block;
}

.brand strong {
  font-size: 1rem;
  letter-spacing: 0.03em;
}

.brand small {
  margin-top: 3px;
  color: #94a3b8;
  font-size: 0.75rem;
}

.library-status {
  display: flex;
  align-items: center;
  gap: 9px;
  color: #cbd5e1;
  font-size: 0.875rem;
}

.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 999px;
  background: var(--teal-bright);
  box-shadow: 0 0 0 4px rgba(45, 212, 191, 0.14);
}

.workspace {
  width: min(1420px, calc(100% - 36px));
  margin: 28px auto 48px;
  display: grid;
  grid-template-columns: minmax(0, 1fr) 24px 340px;
  gap: 0;
  align-items: start;
}

.navigation-toggle-rail {
  position: sticky;
  top: 20px;
  height: min(620px, calc(100vh - 40px));
  display: flex;
  align-items: center;
  justify-content: center;
}

.navigation-toggle {
  width: 24px;
  height: 56px;
  padding: 0;
  display: grid;
  place-items: center;
  color: #475569;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 999px;
  box-shadow: 0 4px 14px rgba(15, 23, 42, 0.12);
  font-size: 1.35rem;
  line-height: 1;
}

.navigation-toggle:hover,
.navigation-toggle:focus-visible {
  color: var(--teal);
  border-color: #7dd3c7;
}

.question-column {
  min-width: 0;
}

.question-card,
.question-index {
  background: var(--surface);
  border: 1px solid var(--line);
  box-shadow: 0 16px 42px rgba(15, 23, 42, 0.08);
}

.question-card {
  min-height: 620px;
  padding: 34px;
  border-radius: 20px;
}

.question-card-head,
.index-head,
.question-meta,
.question-stepper,
.range-controls,
.index-legend {
  display: flex;
  align-items: center;
}

.question-card-head,
.index-head {
  justify-content: space-between;
  gap: 18px;
}

.eyebrow {
  color: var(--teal);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.question-meta {
  margin-top: 8px;
  gap: 10px;
}

.question-number {
  font-size: 1.5rem;
  font-weight: 850;
  letter-spacing: -0.03em;
}

.question-kind {
  padding: 5px 9px;
  color: #475569;
  background: #f1f5f9;
  border-radius: 7px;
  font-size: 0.8rem;
  font-weight: 700;
}

.language-switch {
  display: grid;
  grid-template-columns: 1fr 1fr;
  padding: 4px;
  background: #e8edf3;
  border-radius: 10px;
}

.language-switch button {
  min-width: 72px;
  padding: 8px 12px;
  color: #64748b;
  background: transparent;
  border: 0;
  border-radius: 7px;
  font-size: 0.875rem;
  font-weight: 750;
}

.language-switch button.active {
  color: #ffffff;
  background: var(--navy);
  box-shadow: 0 3px 10px rgba(15, 23, 42, 0.18);
}

.question-content {
  margin-top: 34px;
}

.question-text {
  margin: 0 0 26px;
  font-size: clamp(1.08rem, 1.45vw, 1.28rem);
  font-weight: 400;
  line-height: 1.72;
  letter-spacing: 0.005em;
}

.option-list {
  display: grid;
  gap: 12px;
}

.option-button {
  width: 100%;
  padding: 16px 18px;
  display: grid;
  grid-template-columns: 34px 1fr;
  gap: 13px;
  align-items: start;
  text-align: left;
  color: var(--ink);
  background: #ffffff;
  border: 1px solid var(--line);
  border-radius: 12px;
  cursor: pointer;
  user-select: text;
  transition: border-color 120ms ease, background 120ms ease, transform 120ms ease;
}

.option-button:hover:not([aria-disabled="true"]) {
  border-color: #7dd3c7;
  transform: translateY(-1px);
}

.option-button:focus-visible {
  outline: 3px solid rgba(13, 148, 136, 0.22);
  outline-offset: 2px;
}

.option-button[aria-disabled="true"] {
  cursor: default;
}

.option-button.selected {
  border-color: var(--teal);
  background: var(--teal-soft);
}

.option-button.correct {
  border-color: #34d399;
  background: var(--success-soft);
}

.option-button.incorrect {
  border-color: #f87171;
  background: var(--danger-soft);
}

.option-label {
  width: 30px;
  height: 30px;
  display: grid;
  place-items: center;
  color: #475569;
  background: #eef2f6;
  border-radius: 8px;
  font-weight: 850;
  user-select: none;
}

.selected .option-label {
  color: #ffffff;
  background: var(--teal);
}

.option-text {
  padding-top: 3px;
  font-size: 1rem;
  line-height: 1.58;
  cursor: text;
  user-select: text;
}

.answer-actions {
  margin-top: 28px;
  padding-top: 22px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  border-top: 1px solid var(--line);
}

.selection-hint {
  margin: 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.answer-button-group {
  display: flex;
  gap: 10px;
}

.submit-button,
.question-stepper button,
.range-controls button {
  border: 0;
  border-radius: 10px;
  font-weight: 800;
}

.submit-button {
  padding: 12px 24px;
  color: #ffffff;
  background: var(--teal);
}

.submit-button:disabled {
  cursor: not-allowed;
  color: #94a3b8;
  background: #e2e8f0;
}

.redo-button {
  padding: 12px 20px;
  color: #475569;
  background: #ffffff;
  border: 1px solid var(--line);
  border-radius: 10px;
  font-weight: 800;
}

.redo-button:hover:not(:disabled) {
  color: var(--teal);
  border-color: var(--teal);
}

.redo-button:disabled {
  cursor: not-allowed;
  opacity: 0.45;
}

.result-panel {
  margin-top: 24px;
  padding: 22px;
  background: #f8fafc;
  border: 1px solid var(--line);
  border-left: 4px solid var(--teal);
  border-radius: 12px;
}

.result-panel h3 {
  margin: 0 0 12px;
  font-size: 1rem;
}

.answer-key {
  display: inline-flex;
  margin-left: 8px;
  padding: 4px 9px;
  color: #ffffff;
  background: var(--teal);
  border-radius: 7px;
}

.result-summary,
.option-explanation {
  line-height: 1.68;
}

.result-summary {
  margin: 0;
  color: #334155;
}

.option-explanations {
  margin-top: 18px;
  display: grid;
  gap: 8px;
}

.option-explanation {
  margin: 0;
  color: #475569;
  font-size: 0.92rem;
}

.question-stepper {
  margin-top: 18px;
  justify-content: space-between;
  gap: 16px;
}

.question-stepper button,
.range-controls button {
  padding: 11px 18px;
  color: var(--ink);
  background: #ffffff;
  border: 1px solid var(--line);
}

.question-stepper button:disabled,
.range-controls button:disabled {
  cursor: not-allowed;
  opacity: 0.45;
}

.question-stepper span {
  color: var(--muted);
  font-size: 0.9rem;
  font-variant-numeric: tabular-nums;
}

.question-index {
  position: sticky;
  top: 20px;
  padding: 24px;
  border-radius: 18px;
}

.question-index.navigation-hidden {
  visibility: hidden;
}

.index-head h2 {
  margin: 5px 0 0;
  font-size: 1.15rem;
}

.range-page {
  color: var(--muted);
  font-size: 0.82rem;
  font-variant-numeric: tabular-nums;
}

.number-grid {
  margin-top: 20px;
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 7px;
}

.number-button {
  aspect-ratio: 1;
  min-width: 0;
  display: grid;
  place-items: center;
  color: #64748b;
  background: #f8fafc;
  border: 1px solid transparent;
  border-radius: 7px;
  font-size: 0.7rem;
  font-variant-numeric: tabular-nums;
}

.number-button.available {
  color: #0f172a;
  background: #eef2f6;
  font-weight: 750;
}

.number-button.current {
  color: #ffffff;
  background: var(--teal);
  border-color: var(--teal);
  font-weight: 850;
}

.number-button.answered-correct {
  color: #ffffff;
  background: var(--success);
  font-weight: 800;
}

.number-button.answered-incorrect {
  color: #ffffff;
  background: var(--danger);
  font-weight: 800;
}

.number-button.current {
  border-color: var(--navy);
  box-shadow: inset 0 0 0 1px #ffffff, 0 0 0 2px var(--navy);
}

.number-button:not(.current):hover {
  border-color: #5eead4;
}

.range-controls {
  margin-top: 18px;
  justify-content: space-between;
  gap: 10px;
}

.range-controls button {
  flex: 1;
  padding: 9px 12px;
  font-size: 0.85rem;
}

.index-legend {
  margin-top: 18px;
  padding-top: 16px;
  justify-content: space-between;
  gap: 8px;
  color: var(--muted);
  border-top: 1px solid var(--line);
  font-size: 0.7rem;
}

.index-legend span {
  display: inline-flex;
  align-items: center;
  gap: 5px;
}

.legend-dot {
  width: 8px;
  height: 8px;
  border-radius: 3px;
}

.legend-dot.current {
  background: var(--teal);
}

.legend-dot.available {
  background: #cbd5e1;
}

.legend-dot.correct {
  background: var(--success);
}

.legend-dot.incorrect {
  background: var(--danger);
}

.legend-dot.pending {
  background: #f8fafc;
  border: 1px solid #cbd5e1;
}

.empty-question,
.loading-block,
.error-block {
  min-height: 360px;
  display: grid;
  place-items: center;
  text-align: center;
  color: var(--muted);
  background: #f8fafc;
  border: 1px dashed #cbd5e1;
  border-radius: 14px;
  line-height: 1.7;
}

.empty-question strong {
  display: block;
  margin-bottom: 8px;
  color: var(--ink);
  font-size: 1.1rem;
}

.translation-pending {
  padding: 18px;
  color: var(--amber);
  background: var(--amber-soft);
  border: 1px solid #fed7aa;
  border-radius: 11px;
  line-height: 1.65;
}

@media (max-width: 980px) {
  .workspace {
    grid-template-columns: 1fr;
    gap: 14px;
  }

  .navigation-toggle-rail {
    position: static;
    height: 24px;
  }

  .navigation-toggle {
    width: 56px;
    height: 24px;
  }

  .question-index {
    position: static;
  }

  .number-grid {
    grid-template-columns: repeat(5, minmax(26px, 1fr));
  }
}

@media (max-width: 620px) {
  .topbar {
    min-height: auto;
    padding: 16px 18px;
    align-items: flex-start;
  }

  .brand small,
  .library-status span:last-child {
    display: none;
  }

  .workspace {
    width: min(100% - 20px, 1420px);
    margin-top: 14px;
    gap: 14px;
  }

  .question-card,
  .question-index {
    border-radius: 14px;
  }

  .question-card {
    min-height: 0;
    padding: 20px;
  }

  .question-card-head {
    align-items: flex-start;
  }

  .language-switch button {
    min-width: 58px;
    padding: 7px 8px;
  }

  .question-content {
    margin-top: 24px;
  }

  .answer-actions {
    align-items: stretch;
    flex-direction: column;
  }

  .answer-button-group {
    width: 100%;
  }

  .answer-button-group button {
    flex: 1;
  }

  .question-index {
    padding: 18px;
  }

  .number-grid {
    grid-template-columns: repeat(5, minmax(0, 1fr));
    gap: 5px;
  }

  .number-button {
    border-radius: 5px;
    font-size: 0.62rem;
  }

  .index-legend {
    flex-wrap: wrap;
    justify-content: flex-start;
  }
}

.bank-switch { display: flex; gap: 6px; padding: 4px; border: 1px solid #334155; border-radius: 10px; }
.bank-switch button { border: 0; border-radius: 7px; padding: 10px 14px; background: transparent; color: #cbd5e1; font-weight: 600; }
.bank-switch button.active { background: var(--teal-bright); color: var(--navy); }
.language-switch button:disabled { opacity: .4; cursor: not-allowed; }
@media (max-width: 900px) { .topbar { flex-wrap: wrap; padding: 14px 18px; gap: 12px; } .bank-switch { order: 3; width: 100%; } .bank-switch button { flex: 1; } }

.review-note { color: var(--muted); font-size: 13px; line-height: 1.7; }

.sync-bar{display:flex;justify-content:space-between;align-items:center;gap:12px;max-width:1400px;padding:12px 28px;margin:auto;color:var(--muted);font-size:13px}.sync-actions{display:flex;gap:8px;align-items:center}.sync-actions button{padding:6px 12px;background:white;border:1px solid var(--line);border-radius:6px;color:var(--teal)}.sync-actions button:disabled{opacity:.5;cursor:wait}.sync-actions [hidden]{display:none}@media(max-width:600px){.sync-bar{padding:10px 16px;flex-wrap:wrap}}