:root {
  --bg: #f5f6f8;
  --panel: #ffffff;
  --text: #171a1f;
  --muted: #5c6675;
  --line: #d9dee7;
  --accent: #176c78;
  --accent-dark: #104f58;
  --soft: #eef7f8;
  --sentence: #fbfcfd;
  --node: #f8fafb;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Segoe UI", Arial, sans-serif;
  line-height: 1.55;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 28px 40px;
  border-bottom: 1px solid var(--line);
  background: var(--panel);
}

.eyebrow {
  margin: 0 0 4px;
  color: var(--accent);
  font-weight: 750;
  letter-spacing: 0;
}

h1,
h2,
h3,
p {
  margin: 0;
  letter-spacing: 0;
}

h1 {
  font-size: 28px;
}

h2 {
  font-size: 30px;
}

h3 {
  font-size: 20px;
}

button {
  min-height: 38px;
  border: 1px solid var(--line);
  background: var(--panel);
  color: var(--text);
  border-radius: 6px;
  padding: 8px 14px;
  font-weight: 700;
  cursor: pointer;
}

button:hover {
  border-color: var(--accent);
}

button.primary,
button.speak {
  background: var(--accent);
  border-color: var(--accent);
  color: white;
}

button.primary:hover,
button.speak:hover {
  background: var(--accent-dark);
}

.toolbar {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.app-shell {
  display: grid;
  grid-template-columns: 300px minmax(0, 1fr);
  gap: 24px;
  max-width: 1280px;
  margin: 0 auto;
  padding: 28px 24px 44px;
}

.sidebar {
  align-self: start;
  position: sticky;
  top: 20px;
  display: grid;
  gap: 14px;
}

.search-box {
  display: grid;
  gap: 8px;
  padding: 16px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--muted);
  font-weight: 700;
}

input {
  width: 100%;
  min-height: 42px;
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 8px 10px;
  font: inherit;
  color: var(--text);
  background: white;
}

.system-nav {
  display: grid;
  gap: 10px;
}

.system-tab {
  display: grid;
  justify-items: start;
  gap: 2px;
  min-height: 70px;
  padding: 14px 16px;
  text-align: left;
  background: var(--panel);
}

.system-tab.active {
  border-color: var(--accent);
  background: var(--soft);
}

.system-tab span {
  font-size: 16px;
}

.system-tab small {
  color: var(--muted);
  font-size: 14px;
}

.content {
  display: grid;
  gap: 18px;
}

.hero-panel,
.panel,
.term-card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
}

.hero-panel {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 18px;
  padding: 24px;
}

.hero-zh {
  margin-top: 3px;
  color: var(--accent-dark);
  font-size: 20px;
  font-weight: 800;
}

.hero-subtitle {
  margin-top: 10px;
  color: var(--muted);
  font-size: 16px;
}

.hero-actions,
.term-head,
.term-actions {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.hero-actions {
  justify-content: flex-end;
}

.panel {
  padding: 18px;
}

.panel-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 14px;
}

.panel-head span {
  color: var(--muted);
  font-weight: 700;
}

.sentence-list {
  display: grid;
  gap: 10px;
}

.sentence-row {
  display: grid;
  grid-template-columns: 40px minmax(0, 1fr);
  gap: 12px;
  align-items: start;
  background: var(--sentence);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 14px;
}

.sentence-play {
  width: 38px;
  min-height: 38px;
  padding: 0;
  border-radius: 999px;
  line-height: 1;
}

.sentence-copy {
  display: grid;
  gap: 6px;
}

.sentence-en {
  color: var(--text);
  font-size: 18px;
}

.sentence-zh {
  color: var(--muted);
  font-size: 15px;
}

.map-grid {
  display: grid;
  grid-template-columns: minmax(0, 0.95fr) minmax(0, 1.05fr);
  gap: 18px;
}

.child-tree {
  display: grid;
  gap: 8px;
  padding: 0;
  margin: 0;
  list-style: none;
}

.child-tree li {
  position: relative;
  padding-left: 18px;
}

.child-tree li::before {
  content: "";
  position: absolute;
  left: 4px;
  top: 0;
  bottom: 0;
  width: 1px;
  background: var(--line);
}

.tree-node {
  display: grid;
  width: 100%;
  gap: 2px;
  padding: 10px 12px;
  color: inherit;
  text-align: left;
  text-decoration: none;
  background: var(--node);
  border: 1px solid var(--line);
  border-radius: 8px;
}

.tree-node:hover {
  border-color: var(--accent);
}

.tree-node strong {
  font-size: 16px;
}

.tree-node span {
  color: var(--muted);
  font-weight: 500;
}

.terms {
  display: grid;
  gap: 16px;
}

.term-card {
  padding: 22px;
}

.term-head {
  align-items: start;
  justify-content: space-between;
  margin-bottom: 18px;
}

.term-actions {
  justify-content: flex-end;
}

.term-meta {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-top: 8px;
}

.pill {
  display: inline-flex;
  align-items: center;
  min-height: 26px;
  padding: 3px 9px;
  border-radius: 999px;
  background: var(--soft);
  color: var(--accent-dark);
  font-size: 13px;
  font-weight: 800;
}

.term-play {
  min-width: 88px;
}

.empty {
  color: var(--muted);
}

.detail-intro p {
  color: var(--muted);
}

footer {
  max-width: 1280px;
  margin: 0 auto 32px;
  padding: 0 24px;
}

footer p {
  color: var(--muted);
}

@media (max-width: 900px) {
  .app-shell,
  .map-grid {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
  }
}

@media (max-width: 680px) {
  .topbar,
  .hero-panel,
  .term-head,
  .sentence-row {
    display: grid;
  }

  .topbar {
    padding: 22px;
  }

  .app-shell {
    padding: 22px 16px 36px;
  }

  h1 {
    font-size: 24px;
  }

  h2 {
    font-size: 26px;
  }

  .hero-actions {
    justify-content: start;
  }

  .sentence-row {
    grid-template-columns: 1fr;
  }

  .sentence-play {
    width: 36px;
  }
}