:root {
  color-scheme: light;
  --ink: #17212b;
  --muted: #5d6976;
  --line: #dce4ec;
  --paper: #f6f8fb;
  --panel: #ffffff;
  --blue: #2563eb;
  --green: #16845b;
  --red: #c43d3d;
  --green-soft: #edf8f3;
  --blue-soft: #edf4ff;
  --red-soft: #fff0f0;
  --yellow-soft: #fff8e2;
  --shadow: 0 20px 50px rgba(26, 39, 55, 0.08);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: linear-gradient(180deg, #fff 0%, var(--paper) 48%);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;
  line-height: 1.65;
}
a { color: inherit; }
h1, h2, h3, p { margin: 0; }

[data-site-header] {
  position: sticky;
  top: 0;
  z-index: 20;
}

.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  min-height: 72px;
  padding: 12px max(20px, calc((100vw - 1180px) / 2));
  background: rgba(255, 255, 255, 0.9);
  border-bottom: 1px solid rgba(220, 228, 236, 0.9);
  backdrop-filter: blur(16px);
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
}
.brand-mark,
.subject-mark {
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  border-radius: 8px;
  background: var(--ink);
  color: #fff;
  font-weight: 900;
}
.brand strong,
.brand small { display: block; }
.brand small { color: var(--muted); font-size: 0.82rem; }
.top-nav { display: flex; gap: 8px; align-items: center; }
.top-nav a {
  min-width: 72px;
  padding: 8px 12px;
  border: 1px solid transparent;
  border-radius: 8px;
  color: var(--muted);
  text-align: center;
  text-decoration: none;
}
.top-nav a:hover,
.top-nav a:focus-visible,
.top-nav a[aria-current="page"] {
  border-color: var(--line);
  background: #fff;
  color: var(--ink);
}
.site-footer {
  width: min(1180px, calc(100% - 32px));
  margin: 0 auto;
  padding: 24px 0 40px;
  color: var(--muted);
  font-size: 0.92rem;
}

.home-shell,
.reader-shell {
  width: min(1180px, calc(100% - 32px));
  margin: 0 auto;
  padding: 36px 0 72px;
}
.hero-panel {
  padding: 32px 0 28px;
}
.kicker {
  margin: 0 0 8px;
  color: var(--green);
  font-size: 0.92rem;
  font-weight: 900;
}
.hero-panel h1 {
  font-size: clamp(2.6rem, 8vw, 5.4rem);
  line-height: 1.04;
  letter-spacing: 0;
}
.page-summary {
  max-width: 780px;
  margin-top: 16px;
  color: var(--muted);
  font-size: 1.1rem;
}
.content-section {
  padding: 24px 0;
  border-top: 1px solid var(--line);
}
.section-head {
  margin-bottom: 14px;
}
.section-head h2 {
  font-size: clamp(1.35rem, 3vw, 2.1rem);
}
.content-list {
  display: grid;
  gap: 14px;
}
.content-card {
  display: grid;
  gap: 6px;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--green-soft);
  text-decoration: none;
  box-shadow: var(--shadow);
}
.content-card span,
.content-card small {
  color: var(--muted);
}
.content-card span {
  color: var(--green);
  font-weight: 900;
}
.content-card strong {
  font-size: 1.12rem;
}
.content-card:hover,
.content-card:focus-visible {
  border-color: var(--green);
}
.subject-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 14px;
}
.subject-card {
  min-width: 0;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}
.subject-card h3 {
  margin-top: 12px;
  font-size: 1.2rem;
}
.subject-card p,
.subject-card small {
  color: var(--muted);
}
.subject-card small {
  display: inline-block;
  margin-top: 10px;
  font-weight: 800;
}
.subject-mark.red { background: var(--red); }
.subject-mark.blue { background: var(--blue); }
.subject-mark.green { background: var(--green); }
.subject-mark.teal { background: #0f766e; }

.back-link {
  display: inline-flex;
  margin-bottom: 18px;
  color: var(--muted);
  font-weight: 800;
  text-decoration: none;
}
.back-link:hover,
.back-link:focus-visible { color: var(--ink); }
.reader-hero {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 24px;
  align-items: end;
  padding: 24px 0 22px;
}
.reader-hero h1 {
  font-size: clamp(2rem, 5vw, 4.4rem);
  line-height: 1.08;
}
.reader-hero p:last-child {
  max-width: 760px;
  margin-top: 12px;
  color: var(--muted);
}
.reader-stats {
  display: grid;
  grid-template-columns: repeat(2, auto);
  gap: 8px;
}
.reader-stats span {
  min-height: 42px;
  padding: 8px 12px;
  border: 1px solid #bddfca;
  border-radius: 8px;
  background: var(--green-soft);
  color: #146044;
  font-weight: 900;
  white-space: nowrap;
}
.reader-tools {
  display: grid;
  grid-template-columns: minmax(260px, 420px) auto 1fr;
  gap: 12px;
  align-items: end;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  box-shadow: var(--shadow);
}
.voice-control {
  display: grid;
  gap: 6px;
  color: var(--muted);
  font-size: 0.92rem;
  font-weight: 800;
}
.voice-control select,
.stop-btn {
  min-height: 44px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
  font: inherit;
}
.voice-control select {
  width: 100%;
  padding: 0 12px;
}
.stop-btn {
  padding: 0 16px;
  font-weight: 900;
  cursor: pointer;
}
.stop-btn:hover,
.stop-btn:focus-visible {
  border-color: var(--green);
  color: var(--green);
}
.tts-status {
  min-height: 24px;
  color: var(--green);
  font-size: 0.92rem;
  font-weight: 800;
}
.tts-status.unsupported { color: var(--red); }
.reader-unit-nav {
  position: sticky;
  top: 72px;
  z-index: 10;
  display: flex;
  gap: 8px;
  overflow-x: auto;
  padding: 12px 0;
  margin: 14px 0 10px;
  background: rgba(246, 248, 251, 0.94);
  backdrop-filter: blur(12px);
}
.reader-unit-nav a {
  flex: 0 0 auto;
  min-width: 78px;
  padding: 8px 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--muted);
  text-align: center;
  text-decoration: none;
  font-weight: 900;
}
.reader-unit-nav a:hover,
.reader-unit-nav a:focus-visible {
  border-color: var(--green);
  color: var(--green);
}
.reader-units {
  display: grid;
  gap: 18px;
}
.reader-unit {
  scroll-margin-top: 136px;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  box-shadow: var(--shadow);
}
.reader-unit-header {
  padding: 18px 20px;
  border-bottom: 1px solid var(--line);
  background: linear-gradient(135deg, var(--green-soft), #fff);
}
.reader-unit-header p {
  margin: 0 0 4px;
  color: var(--green);
  font-weight: 900;
}
.reader-unit-header h2 {
  margin: 0;
  font-size: clamp(1.3rem, 3vw, 2.1rem);
}
.reader-unit-body {
  padding: 10px 20px 20px;
}
.reader-section-title {
  margin: 18px 0 8px;
  color: var(--muted);
  font-size: 1rem;
}
.reader-line {
  display: grid;
  gap: 8px;
  padding: 12px 0;
  border-bottom: 1px solid #edf1f5;
}
.reader-line:last-child { border-bottom: 0; }
.english-flow {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: baseline;
  font-size: 1.04rem;
}
.speaker {
  color: var(--blue);
  font-weight: 900;
}
.utterance-text { display: inline; }
.sentence-chunk {
  display: inline-flex;
  align-items: center;
  min-height: 32px;
  gap: 5px;
  margin-right: 7px;
  border-radius: 6px;
  cursor: pointer;
}
.sentence-chunk:hover .sentence,
.sentence-chunk:focus-within .sentence,
.sentence-chunk.is-linked .sentence { color: var(--green); }
.read-btn {
  display: inline-grid;
  place-items: center;
  width: 28px;
  height: 28px;
  flex: 0 0 28px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: #fff;
  color: var(--green);
  cursor: pointer;
  vertical-align: middle;
}
.read-btn svg {
  width: 14px;
  height: 14px;
  fill: currentColor;
}
.read-btn:hover,
.read-btn:focus-visible,
.read-btn.is-speaking {
  border-color: var(--green);
  background: var(--green);
  color: #fff;
}
.translations {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.translation {
  min-height: 32px;
  padding: 5px 9px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--paper);
  color: var(--ink);
  cursor: pointer;
  font: inherit;
  text-align: left;
}
.translation-text {
  filter: blur(5px);
  opacity: 0.34;
  transition: filter 0.15s ease, opacity 0.15s ease;
}
.translation.is-visible,
.translation:focus {
  border-color: #bddfca;
  background: var(--green-soft);
}
.translation.is-visible .translation-text,
.translation:focus .translation-text {
  filter: none;
  opacity: 1;
}
.translation.is-linked { color: var(--green); }
.back-top {
  position: fixed;
  right: 18px;
  bottom: 18px;
  z-index: 30;
  min-width: 52px;
  min-height: 44px;
  padding: 8px 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--green);
  box-shadow: var(--shadow);
  cursor: pointer;
  font-weight: 900;
  opacity: 0;
  pointer-events: none;
  transform: translateY(8px);
  transition: opacity 0.15s ease, transform 0.15s ease;
}
.back-top.is-visible {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}

@media (max-width: 860px) {
  .site-header {
    align-items: flex-start;
    flex-direction: column;
  }
  .top-nav {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    width: 100%;
  }
  .top-nav a {
    min-width: 0;
    width: auto;
  }
  .reader-unit-nav { top: 132px; }
  .dictation-panel.is-active { top: 198px; }
  .reader-unit,
  .vocab-unit { scroll-margin-top: 204px; }
  .vocab-shell.is-dictation-active .vocab-unit { scroll-margin-top: 360px; }
  .subject-grid,
  .reader-hero,
  .reader-tools {
    grid-template-columns: 1fr;
  }
  .reader-stats { width: fit-content; }
}
@media (max-width: 620px) {
  .home-shell,
  .reader-shell,
  .site-footer {
    width: min(100% - 24px, 1180px);
  }
  .reader-stats { grid-template-columns: 1fr; }
  .reader-unit-body { padding: 8px 14px 16px; }
  .reader-unit-header { padding: 16px 14px; }
  .english-flow { display: block; }
  .speaker {
    display: inline-block;
    margin-right: 6px;
  }
  .sentence-chunk { margin: 3px 4px 3px 0; }
}
@media print {
  body { background: #fff; color: #111; }
  [data-site-header] { position: static; }
  .site-header { border-bottom: 1px solid #ddd; }
  .reader-tools,
  .dictation-panel,
  .reader-unit-nav,
  .read-btn,
  .back-top { display: none; }
  .home-shell,
  .reader-shell {
    width: 100%;
    padding: 0;
  }
  .content-card,
  .subject-card,
  .reader-unit {
    box-shadow: none;
    break-inside: avoid;
  }
  .translation-text {
    filter: none;
    opacity: 1;
  }
}

.vocab-shell .reader-tools {
  margin-bottom: 12px;
}
.dictation-panel {
  margin: 0 0 14px;
}
.dictation-panel.is-active {
  position: sticky;
  top: 138px;
  z-index: 9;
  padding: 10px 0;
  background: rgba(246, 248, 251, 0.96);
  backdrop-filter: blur(12px);
}
.dictation-toolbar {
  display: flex;
  gap: 8px;
  align-items: center;
  margin-bottom: 10px;
}
.dictation-toggle {
  min-height: 44px;
  padding: 0 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
  cursor: pointer;
  font: inherit;
  font-weight: 900;
}
.dictation-toggle:hover,
.dictation-toggle:focus-visible {
  border-color: var(--green);
  color: var(--green);
}
.dictation-panel.is-active .dictation-toggle {
  border-color: var(--green);
  background: var(--green);
  color: #fff;
}
.dictation-tray {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: flex-start;
  min-height: 78px;
  padding: 12px;
  margin-bottom: 12px;
  border: 1px dashed #bddfca;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.92);
  box-shadow: var(--shadow);
  max-height: min(32vh, 220px);
  overflow-y: auto;
}
.dictation-tray[hidden] {
  display: none;
}
.dictation-chip {
  min-height: 36px;
  padding: 5px 10px;
  border: 1px solid #bddfca;
  border-radius: 8px;
  background: var(--green-soft);
  color: var(--ink);
  cursor: pointer;
  font: inherit;
  font-weight: 900;
}
.dictation-chip:hover,
.dictation-chip:focus-visible {
  border-color: var(--green);
  color: var(--green);
}
.vocab-shell.is-dictation-active .vocab-word span {
  color: var(--green);
  cursor: pointer;
  text-decoration: underline;
  text-underline-offset: 3px;
}
.vocab-shell.is-dictation-active .vocab-unit {
  scroll-margin-top: 310px;
}
.vocab-units {
  display: grid;
  gap: 14px;
}
.vocab-unit {
  scroll-margin-top: 136px;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  box-shadow: var(--shadow);
}
.vocab-table-wrap {
  overflow-x: auto;
}
.vocab-table {
  width: 100%;
  border-collapse: collapse;
}
.vocab-table th,
.vocab-table td {
  padding: 13px 16px;
  border-top: 1px solid #edf1f5;
  text-align: left;
  vertical-align: middle;
}
.vocab-table th {
  background: #f8fafc;
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 900;
}
.vocab-table tr:hover td {
  background: #f8fbff;
}
.vocab-word {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  min-width: 190px;
  color: var(--ink);
  font-weight: 900;
}
.vocab-word .read-btn {
  flex: 0 0 28px;
}
.phonetic {
  color: var(--muted);
  font-family: "Segoe UI", "Arial", sans-serif;
  white-space: nowrap;
}
.muted-text {
  color: #9aa5b1;
}
@media (max-width: 620px) {
  .vocab-table th,
  .vocab-table td {
    padding: 11px 12px;
  }
  .vocab-word {
    min-width: 160px;
  }
}
@media print {
  .vocab-unit {
    box-shadow: none;
    break-inside: avoid;
  }
}
@media (max-width: 860px) {
  /* Mobile sticky header offset for vocabulary anchors. */
  .vocab-unit { scroll-margin-top: 204px; }
}
.story-page .reader-unit-body {
  padding: 18px 20px 20px;
}
.story-layout {
  display: grid;
  grid-template-columns: minmax(280px, 44%) minmax(0, 1fr);
  gap: 18px;
  align-items: start;
}
.story-figure {
  margin: 0;
}
.story-figure img {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}
.story-text {
  min-width: 0;
}
.story-page .reader-line:first-child {
  padding-top: 0;
}
.story-page .reader-line:last-child {
  border-bottom: 0;
}
@media (max-width: 860px) {
  .story-layout {
    grid-template-columns: 1fr;
  }
}
@media print {
  .story-layout {
    grid-template-columns: 42% 1fr;
  }
  .story-figure img {
    box-shadow: none;
  }
}

/* Grammar topic pages */
.grammar-shell .reader-tools {
  margin-bottom: 12px;
}
.grammar-unit-body {
  display: grid;
  gap: 14px;
  padding-top: 16px;
}
.grammar-prose {
  color: var(--ink);
}
.grammar-table-wrap {
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}
.grammar-table {
  width: 100%;
  border-collapse: collapse;
  min-width: 620px;
}
.grammar-table th,
.grammar-table td {
  padding: 12px 14px;
  border-top: 1px solid #edf1f5;
  text-align: left;
  vertical-align: top;
}
.grammar-table th {
  background: #f8fafc;
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 900;
}
.grammar-table tr:first-child th,
.grammar-table tr:first-child td {
  border-top: 0;
}
.grammar-table tr:hover td {
  background: #f8fbff;
}
.grammar-callout {
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}
.grammar-callout.is-note {
  border-color: #c9ddff;
  background: var(--blue-soft);
}
.grammar-callout.is-tip {
  border-color: #bddfca;
  background: var(--green-soft);
}
.grammar-callout.is-warning {
  border-color: #f1c7c7;
  background: var(--red-soft);
}
.grammar-callout p + p {
  margin-top: 8px;
}
.grammar-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 12px;
}
.grammar-example-list {
  display: grid;
  gap: 0;
  border-top: 1px solid #edf1f5;
  border-bottom: 1px solid #edf1f5;
}
.grammar-example-line {
  padding: 10px 0;
}
.formula {
  display: inline-block;
  padding: 1px 7px;
  border-radius: 6px;
  background: #f8fafc;
  color: #0f766e;
  font-weight: 900;
}
.grammar-list {
  margin: 0;
  padding-left: 1.35em;
}
.grammar-footer-note {
  padding: 12px 14px;
  border: 1px solid #bddfca;
  border-radius: 8px;
  background: var(--green-soft);
  color: var(--muted);
  font-weight: 800;
}
@media (max-width: 620px) {
  .grammar-table {
    min-width: 560px;
  }
  .grammar-table th,
  .grammar-table td {
    padding: 10px 12px;
  }
}
@media print {
  .grammar-table-wrap,
  .grammar-callout {
    break-inside: avoid;
  }
}