:root {
  --ink: #1a1f2e;
  --muted: #5c6578;
  --line: rgba(26, 31, 46, 0.08);
  --accent: #4FC3F7;
  --accent-soft: rgba(79, 195, 247, 0.12);
  --card: #ffffff;
  --display: "Fraunces", Georgia, serif;
  --font: "DM Sans", system-ui, sans-serif;
  --radius: 18px;
  --shadow: 0 14px 40px rgba(26, 31, 46, 0.08);
}

.hero-panel {
  margin-bottom: 1.25rem;
}

.hero-panel p {
  margin: 0;
  color: var(--muted);
  max-width: 42rem;
}

.tool-pills {
  display: flex;
  gap: 0.5rem;
  margin: 1rem 0;
}

.tool-pill {
  padding: 0.35rem 0.85rem;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: #fff;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--muted);
  font: inherit;
  cursor: pointer;
}

.tool-pill.is-disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

.tool-pill.is-active {
  background: var(--accent-soft);
  border-color: rgba(61, 126, 166, 0.35);
  color: var(--accent);
}

.coming-soon {
  background: var(--card);
  border: 1px dashed rgba(61, 126, 166, 0.35);
  border-radius: var(--radius);
  padding: 2.5rem 1.5rem;
  text-align: center;
  box-shadow: var(--shadow);
}

.coming-soon h2 {
  margin: 0 0 0.5rem;
  font-family: var(--display);
}

.coming-soon p {
  margin: 0;
  color: var(--muted);
}

.section-label {
  margin: 0 0 0.75rem;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
}

.comic-subtabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin-bottom: 1.25rem;
}

.comic-subtab {
  border: 1px solid var(--line);
  background: #fff;
  font: inherit;
  font-weight: 600;
  font-size: 0.85rem;
  padding: 0.45rem 0.9rem;
  border-radius: 999px;
  cursor: pointer;
  color: var(--muted);
}

.comic-subtab.is-active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.comic-series-title {
  margin: 0 0 0.25rem;
  font-family: var(--display);
  font-size: 1.35rem;
}

.comic-series-desc {
  margin: 0 0 1rem;
  color: var(--muted);
  font-size: 0.92rem;
}

.comic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 1rem;
}

.comic-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fff;
  overflow: hidden;
  box-shadow: var(--shadow);
  cursor: pointer;
  text-align: left;
  padding: 0;
  font: inherit;
  color: inherit;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.comic-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 16px 36px rgba(26, 31, 46, 0.12);
}

.comic-card.is-law-card {
  outline: 2px solid rgba(61, 126, 166, 0.25);
}

.comic-thumb-wrap {
  aspect-ratio: 3 / 4;
  background: #eef2f7;
  overflow: hidden;
}

.comic-thumb-wrap img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: top;
}

.comic-card-body {
  padding: 0.75rem 0.85rem 0.9rem;
}

.comic-card-body strong {
  display: block;
  font-size: 0.88rem;
  line-height: 1.3;
}

.comic-card-body span {
  display: block;
  margin-top: 0.25rem;
  font-size: 0.75rem;
  color: var(--muted);
}

.tool-section {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.25rem;
  box-shadow: var(--shadow);
}

.tool-section h2 {
  margin: 0 0 0.35rem;
  font-family: var(--display);
  font-size: 1.1rem;
}

.tool-section p {
  margin: 0;
  color: var(--muted);
}

.comics-reader {
  position: fixed;
  inset: 0;
  z-index: 100;
}

.reader-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(10, 14, 24, 0.82);
}

.reader-panel {
  position: relative;
  z-index: 1;
  display: flex;
  flex-direction: column;
  max-width: 720px;
  max-height: calc(100vh - 2rem);
  margin: 1rem auto;
  background: #fff;
  border-radius: 14px;
  overflow: hidden;
  box-shadow: 0 24px 64px rgba(0, 0, 0, 0.35);
}

.reader-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 0.75rem;
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--line);
  background: #f8fafc;
}

.reader-topic {
  display: block;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent);
}

.reader-title {
  display: block;
  font-size: 0.95rem;
  line-height: 1.3;
}

.reader-close {
  border: none;
  background: transparent;
  font-size: 1.6rem;
  line-height: 1;
  cursor: pointer;
  color: var(--muted);
  padding: 0 0.25rem;
}

.reader-body {
  flex: 1;
  overflow: auto;
  background: #111;
}

.reader-body img {
  display: block;
  width: 100%;
  height: auto;
}

.reader-caption {
  margin: 0;
  padding: 1rem 1.15rem 1.2rem;
  background: #f8fafc;
  border-top: 1px solid var(--line);
  color: var(--ink);
}

.reader-caption-zh {
  margin: 0 0 0.45rem;
  font-size: 1.02rem;
  font-weight: 700;
  line-height: 1.55;
}

.reader-caption-en {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.5;
  color: var(--muted);
}

.reader-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  padding: 0.75rem 1rem;
  border-top: 1px solid var(--line);
  background: #f8fafc;
}

.reader-footer-right {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  justify-content: flex-end;
}

.reader-nav.is-subtopic {
  background: var(--accent-soft);
  border-color: rgba(61, 126, 166, 0.35);
  color: var(--accent);
}
.quiz-section {
  margin-top: 2rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--line);
}

.quiz-heading {
  margin: 0 0 1rem;
  font-family: var(--display);
  font-size: 1.25rem;
}

.quiz-card {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem 1.1rem;
  margin-bottom: 0.85rem;
  box-shadow: var(--shadow);
}

.quiz-num {
  margin: 0 0 0.35rem;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
}

.quiz-question {
  margin: 0 0 0.75rem;
  font-weight: 600;
}

.quiz-frac {
  display: inline-grid;
  grid-template-rows: auto auto auto;
  justify-items: center;
  vertical-align: middle;
  margin: 0 0.12em;
  font-size: 0.82em;
  line-height: 1;
}

.quiz-frac-num,
.quiz-frac-den {
  padding: 0 0.2em;
}

.quiz-frac-bar {
  width: 100%;
  min-width: 0.95em;
  border-top: 1.5px solid currentColor;
}

.quiz-options {
  display: grid;
  gap: 0.5rem;
}

.quiz-option {
  display: flex;
  align-items: flex-start;
  gap: 0.65rem;
  width: 100%;
  text-align: left;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #fff;
  padding: 0.65rem 0.85rem;
  font: inherit;
  cursor: pointer;
  transition: border-color 0.15s ease, background 0.15s ease;
}

.quiz-option:hover:not(:disabled) {
  border-color: rgba(61, 126, 166, 0.45);
  background: #f8fbfd;
}

.quiz-option:disabled {
  cursor: default;
}

.quiz-letter {
  flex: 0 0 auto;
  width: 1.6rem;
  height: 1.6rem;
  border-radius: 8px;
  display: grid;
  place-items: center;
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 700;
  font-size: 0.82rem;
}

.quiz-option-text {
  flex: 1;
  line-height: 1.4;
}

.quiz-option.is-selected {
  border-color: #2d6a4f;
  background: #edf7f1;
}

.quiz-option.is-correct-option {
  border-color: #2d6a4f;
  background: #edf7f1;
}

.quiz-option.is-wrong-option {
  border-color: #9b2335;
  background: #fdf2f4;
}

.quiz-feedback {
  margin: 0.65rem 0 0;
  font-size: 0.9rem;
}

.quiz-feedback.is-correct {
  color: #2d6a4f;
}

.quiz-feedback.is-wrong {
  color: #9b2335;
}

.reader-nav {
  border: 1px solid var(--line);
  background: #fff;
.sci-tool {
  margin-top: 0.5rem;
}

.sci-module-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin-bottom: 1rem;
}

.sci-module-pill {
  border: 1px solid var(--line);
  background: #fff;
  font: inherit;
  font-weight: 600;
  font-size: 0.82rem;
  padding: 0.4rem 0.85rem;
  border-radius: 999px;
  cursor: pointer;
  color: var(--muted);
  transition: background 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

.sci-module-pill.is-active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.sci-walkthrough {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.35rem 1.25rem 1.1rem;
  box-shadow: var(--shadow);
}

.sci-walkthrough-head h2 {
  margin: 0 0 0.35rem;
  font-family: var(--display);
  font-size: 1.25rem;
}

.sci-prompt {
  margin: 0 0 1rem;
  color: var(--ink);
  font-weight: 600;
  font-size: 1.05rem;
}

.sci-progress {
  margin-bottom: 1rem;
}

.sci-progress-meta {
  display: flex;
  justify-content: space-between;
  gap: 0.75rem;
  font-size: 0.78rem;
  color: var(--muted);
  margin-bottom: 0.35rem;
}

.sci-ref {
  text-align: right;
}

.sci-progress-bar {
  height: 6px;
  border-radius: 999px;
  background: #e8eef4;
  overflow: hidden;
}

.sci-progress-fill {
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, #3d7ea6, #5ba4c9);
  transition: width 0.45s cubic-bezier(0.4, 0, 0.2, 1);
}

.sci-step-stage {
  min-height: 9.5rem;
  position: relative;
}

.sci-step-panel {
  opacity: 1;
  transform: translateY(0);
  transition: opacity 0.28s ease, transform 0.28s ease;
}

.sci-step-panel.is-exiting {
  opacity: 0;
  transform: translateY(-12px);
}

.sci-step-panel.is-entering {
  opacity: 0;
  transform: translateY(16px);
}

.sci-step-kicker {
  margin: 0 0 0.5rem;
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--accent);
}

.sci-step-body {
  margin: 0 0 0.85rem;
  color: var(--muted);
  line-height: 1.55;
}

.sci-step-math {
  margin: 0;
  padding: 0.85rem 1rem;
  border-radius: 12px;
  background: #f3f7fb;
  border: 1px solid rgba(61, 126, 166, 0.15);
  font-family: "DM Sans", sans-serif;
  font-size: 1.05rem;
  font-weight: 700;
  line-height: 1.5;
  white-space: pre-wrap;
  color: var(--ink);
}

.sci-answer-banner {
  margin-top: 1rem;
  padding: 0.75rem 1rem;
  border-radius: 12px;
  background: rgba(61, 214, 140, 0.12);
  border: 1px solid rgba(61, 214, 140, 0.35);
  font-size: 0.95rem;
}

.sci-answer-banner strong {
  font-size: 1.1rem;
}

.sci-nav {
  display: flex;
  justify-content: space-between;
  gap: 0.75rem;
  margin-top: 1.15rem;
}

.sci-nav-btn {
  border: 1px solid var(--line);
  background: #fff;
  font: inherit;
  font-weight: 600;
  font-size: 0.88rem;
  padding: 0.55rem 1rem;
  border-radius: 999px;
  cursor: pointer;
  color: var(--ink);
  transition: background 0.15s ease, border-color 0.15s ease;
}

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

.sci-nav-btn.is-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.sci-nav-btn.is-primary:hover:not(:disabled) {
  filter: brightness(1.05);
}

/* Factor tool ??aligned math visualizations */
.sci-step-math--mono {
  font-family: ui-monospace, "Cascadia Code", "Consolas", monospace;
  white-space: pre-wrap;
  tab-size: 4;
}

.math-viz {
  margin: 0;