:root {
  --bg: #f4f7fb;
  --bg-elevated: #ffffff;
  --surface: #edf3ff;
  --surface-strong: #dfe9ff;
  --text: #1d2a3a;
  --muted: #5a6a82;
  --accent: #4568dc;
  --accent-strong: #2e4bb9;
  --accent-soft: rgba(69, 104, 220, 0.12);
  --success: #1ca57a;
  --border: rgba(29, 42, 58, 0.08);
  --shadow: 0 18px 48px rgba(70, 98, 172, 0.12);
}

body[data-theme='dark'] {
  --bg: #101827;
  --bg-elevated: #172133;
  --surface: #1f2c42;
  --surface-strong: #2a3d5d;
  --text: #edf3ff;
  --muted: #b9c6d8;
  --accent: #8aaaef;
  --accent-strong: #b8cbff;
  --accent-soft: rgba(138, 170, 239, 0.18);
  --success: #5ed2a2;
  --border: rgba(237, 243, 255, 0.08);
  --shadow: 0 18px 48px rgba(3, 6, 20, 0.45);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: Inter, 'Segoe UI', sans-serif;
  background: linear-gradient(180deg, var(--bg) 0%, #eef3ff 100%);
  color: var(--text);
  transition: background 0.2s ease, color 0.2s ease;
}

body[data-theme='dark'] {
  background: linear-gradient(180deg, var(--bg) 0%, #0b1322 100%);
}

button,
input,
select {
  font: inherit;
}

.app-shell {
  max-width: 1100px;
  margin: 0 auto;
  padding: 24px 18px 48px;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 20px;
}

.eyebrow {
  margin: 0 0 6px;
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
}

h1 {
  margin: 0;
  font-size: clamp(1.9rem, 4vw, 3rem);
  line-height: 1.1;
}

.theme-toggle {
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  color: var(--text);
  border-radius: 999px;
  width: 48px;
  height: 48px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: var(--shadow);
  transition: transform 0.15s ease, border-color 0.2s ease, background 0.2s ease;
}

.theme-toggle:hover {
  transform: translateY(-1px);
}

.theme-toggle .icon {
  font-size: 1.25rem;
}

.main-category-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 16px;
}

.main-tab {
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  color: var(--text);
  border-radius: 12px;
  padding: 12px 18px;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.2s ease;
}

.main-tab:hover {
  background: var(--accent-soft);
}

.main-tab.is-active {
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent-strong) 100%);
  color: white;
  box-shadow: 0 12px 24px rgba(69, 104, 220, 0.2);
}

.tabbar {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  padding: 10px;
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  border-radius: 18px;
  box-shadow: var(--shadow);
  margin-bottom: 22px;
}

.tab {
  flex: 1 1 140px;
  border: 1px solid transparent;
  background: transparent;
  color: var(--muted);
  border-radius: 12px;
  padding: 12px 14px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
}

.tab:hover {
  background: var(--accent-soft);
  color: var(--text);
}

.tab.is-active {
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent-strong) 100%);
  color: white;
  box-shadow: 0 12px 24px rgba(69, 104, 220, 0.2);
}

.word-subtabs {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 22px;
}

.word-subtab {
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  border-radius: 999px;
  padding: 10px 14px;
  cursor: pointer;
  font-weight: 600;
  transition: all 0.2s ease;
}

.word-subtab:hover {
  background: var(--accent-soft);
}

.word-subtab.is-active {
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent-strong) 100%);
  color: white;
  border-color: transparent;
}

.page-content {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 24px;
  box-shadow: var(--shadow);
  padding: 24px;
}

.tab-panel {
  min-height: 320px;
}

.group {
  margin-top: 18px;
  margin-bottom: 28px;
}

.group:first-child {
  margin-top: 0;
}

.group:last-child {
  margin-bottom: 0;
}

.group h2 {
  margin: 0 0 14px;
  font-size: clamp(1.2rem, 2.2vw, 1.7rem);
}

.table-shell {
  overflow-x: auto;
  border: 1px solid var(--border);
  border-radius: 16px;
  background: var(--surface);
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  min-width: 520px;
}

.data-table th,
.data-table td {
  padding: 14px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border);
  vertical-align: top;
}

.data-table thead th {
  background: var(--surface-strong);
  color: var(--text);
  font-size: 0.82rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.data-table tbody tr:nth-child(even) {
  background: rgba(255, 255, 255, 0.02);
}

.data-table tbody tr:hover {
  background: var(--accent-soft);
}

.data-table td {
  color: var(--text);
}

.data-table td:first-child,
.data-table th:first-child,
.data-table td:nth-child(3),
.data-table th:nth-child(3),
.bold-text {
  font-weight: 700;
}

.number-table thead th {
  font-weight: 700;
}

.number-table tbody td:first-child,
.number-table tbody td:nth-child(3) {
  font-weight: 400;
}

.number-table tbody td:nth-child(2) {
  font-weight: 700;
}

.grammar-card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 22px;
}

.grammar-card h2 {
  margin-top: 0;
  margin-bottom: 18px;
}

.grammar-card h3 {
  margin: 0 0 12px;
}

.grammar-card h3 span {
  font-size: 0.9em;
  color: var(--muted);
  font-weight: 600;
}

.grammar-card p {
  margin: 0 0 16px;
  line-height: 1.7;
}

.rule-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 18px;
  margin: 20px 0;
}

.rule-box,
.summary-box {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 18px;
}

.mini-rule {
  display: grid;
  grid-template-columns: 68px 1fr;
  gap: 12px;
  align-items: start;
  padding: 12px 0;
  border-top: 1px solid var(--border);
}

.mini-rule:first-of-type {
  border-top: none;
  padding-top: 0;
}

.mini-label {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 42px;
  border-radius: 10px;
  background: var(--accent-soft);
  color: var(--accent-strong);
  font-weight: 800;
}

.summary-box ul {
  margin: 0;
  padding-left: 18px;
  line-height: 1.8;
}

.grammar-table-shell {
  overflow-x: auto;
  margin: 18px 0;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: var(--bg-elevated);
}

.grammar-table {
  width: 100%;
  min-width: 420px;
  border-collapse: collapse;
}

.grammar-table th,
.grammar-table td {
  border-bottom: 1px solid var(--border);
  padding: 12px 14px;
  text-align: left;
}

.grammar-table thead th {
  background: var(--surface-strong);
}

.grammar-card .examples {
  margin-top: 18px;
  padding-left: 18px;
}

.weekday-note {
  margin-top: 18px;
}

.empty-state {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 280px;
  border: 1px dashed var(--border);
  border-radius: 18px;
  color: var(--muted);
  background: var(--surface);
  text-align: center;
  padding: 24px;
}

@media (max-width: 640px) {
  .app-shell {
    padding-left: 12px;
    padding-right: 12px;
  }

  .topbar {
    align-items: flex-start;
  }

  .tabbar {
    padding: 8px;
  }

  .tab {
    flex-basis: calc(50% - 8px);
  }

  .page-content {
    padding: 14px;
  }
}