/* UI/UX Pro Max · knowledge-base pass: accessible, dense, product-team oriented */
:root {
  --font-display: ui-serif, Georgia, "Times New Roman", serif;
  --font-body: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --color-bg: #f8fafc;
  --color-paper: #ffffff;
  --color-paper-2: #f1f5f9;
  --color-ink: #172033;
  --color-muted: #586579;
  --color-line: #dbe3ee;
  --color-accent: #2563eb;
  --color-accent-2: #0f766e;
  --color-accent-3: #92400e;
  --color-soft: #eaf3ff;
  --color-success-soft: #e8f6f0;
  --color-danger-soft: #fff0e8;
  --color-focus: #1d4ed8;
  --shadow-soft: 0 10px 28px rgba(15, 23, 42, 0.08);
  --radius: 8px;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.5rem;
  --space-6: 2rem;
  --space-7: 2.75rem;
  --max: 1220px;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  overflow-x: clip;
}

body {
  background: var(--color-bg);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.62;
}

.skip-link {
  background: var(--color-ink);
  color: var(--color-paper);
  left: 1rem;
  padding: 0.7rem 0.9rem;
  position: fixed;
  top: -5rem;
  z-index: 1000;
}

.skip-link:focus {
  top: 1rem;
}

a {
  color: var(--color-accent);
  text-decoration-thickness: 0.08em;
  text-underline-offset: 0.18em;
}

a:hover {
  color: var(--color-accent-2);
}

.site-header {
  border-bottom: 1px solid var(--color-line);
  background: rgba(248, 250, 252, 0.96);
  position: sticky;
  top: 0;
  z-index: 20;
  backdrop-filter: blur(12px);
}

.nav {
  width: min(100% - 2rem, var(--max));
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  padding: 0.65rem 0;
}

.brand {
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: 1.1rem;
  font-weight: 800;
  text-decoration: none;
  white-space: nowrap;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 0.15rem;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.nav-links a {
  border-radius: var(--radius);
  color: var(--color-muted);
  font-size: 0.84rem;
  font-weight: 700;
  line-height: 1;
  min-height: 2.5rem;
  padding: 0.74rem 0.62rem;
  text-decoration: none;
  white-space: nowrap;
}

.nav-links a:hover,
.nav-links a.active {
  background: var(--color-paper-2);
  color: var(--color-ink);
}

.hero,
.page-head,
.section,
.footer-inner {
  width: min(100% - 2rem, var(--max));
  margin: 0 auto;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(280px, 0.72fr);
  gap: var(--space-6);
  align-items: center;
  padding: var(--space-6) 0 var(--space-5);
}

.hero h1,
.page-head h1 {
  font-family: var(--font-display);
  font-style: normal;
  font-size: clamp(2rem, 3vw, 2.85rem);
  line-height: 1.03;
  letter-spacing: 0;
  margin: 0;
  overflow-wrap: anywhere;
}

.hero p,
.page-head p {
  color: var(--color-muted);
  font-size: 1rem;
  max-width: 72ch;
}

.hero-panel {
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-soft);
  padding: var(--space-5);
}

.stat-row {
  border-top: 1px solid var(--color-line);
  display: grid;
  gap: 0.3rem;
  padding: var(--space-4) 0;
}

.stat-row:first-child {
  border-top: 0;
  padding-top: 0;
}

.stat-row strong {
  font-size: 1.6rem;
  line-height: 1;
}

.stat-row span {
  color: var(--color-muted);
  font-size: 0.93rem;
}

.page-head {
  padding: var(--space-6) 0 var(--space-3);
}

.section {
  padding: var(--space-5) 0;
}

.section.band {
  width: 100%;
  background: var(--color-paper);
  border-block: 1px solid var(--color-line);
}

.section.band > .inner {
  width: min(100% - 2rem, var(--max));
  margin: 0 auto;
}

h2,
h3 {
  font-family: var(--font-display);
  font-style: normal;
  letter-spacing: 0;
}

h2 {
  font-size: clamp(1.45rem, 2.5vw, 2.05rem);
  line-height: 1.12;
  margin: 0 0 var(--space-4);
}

h3 {
  font-family: var(--font-body);
  font-size: 1.05rem;
  font-weight: 800;
  line-height: 1.2;
  margin: 0 0 var(--space-2);
}

p {
  margin: 0 0 var(--space-4);
}

.lead {
  color: var(--color-muted);
  font-size: 1rem;
  max-width: 76ch;
}

.grid {
  display: grid;
  gap: var(--space-4);
}

.grid.two {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.grid.three {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.grid.four {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.card {
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  padding: var(--space-4);
}

.card.tint {
  background: var(--color-soft);
}

.card.success {
  background: var(--color-success-soft);
}

.card.warning {
  background: var(--color-danger-soft);
}

.kicker {
  color: var(--color-accent);
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-2);
  text-transform: uppercase;
}

.lesson-layout {
  align-items: start;
  display: grid;
  gap: var(--space-5);
  grid-template-columns: 15rem minmax(0, 1fr);
  min-width: 0;
}

.toc {
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  padding: var(--space-4);
  position: sticky;
  top: 4.5rem;
}

.toc strong {
  display: block;
  font-size: 0.82rem;
  margin-bottom: var(--space-2);
  text-transform: uppercase;
}

.toc a {
  color: var(--color-muted);
  display: block;
  font-size: 0.92rem;
  padding: 0.35rem 0;
  text-decoration: none;
}

.toc a:hover {
  color: var(--color-accent);
}

.content-stack {
  display: grid;
  gap: var(--space-5);
  min-width: 0;
}

.callout {
  background: var(--color-paper-2);
  border: 1px solid var(--color-line);
  border-left: 4px solid var(--color-accent);
  border-radius: var(--radius);
  padding: var(--space-4);
}

.callout.warning {
  background: var(--color-danger-soft);
  border-left-color: var(--color-accent-3);
}

.dense-table {
  border-collapse: collapse;
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  contain: inline-size;
  display: block;
  font-size: 0.93rem;
  max-width: 100%;
  overflow-x: auto;
  width: 100%;
}

.dense-table table {
  border-collapse: collapse;
  min-width: 680px;
  width: 100%;
}

.dense-table th,
.dense-table td {
  border-bottom: 1px solid var(--color-line);
  padding: 0.7rem 0.85rem;
  text-align: left;
  vertical-align: top;
}

.dense-table th {
  background: var(--color-paper-2);
  color: var(--color-ink);
  font-size: 0.78rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.dense-table tr:last-child td {
  border-bottom: 0;
}

.term {
  border-bottom: 1px dotted var(--color-accent);
  color: var(--color-ink);
  cursor: help;
  font-weight: 800;
  position: relative;
}

.term:focus-visible {
  border-radius: 4px;
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

.term-tooltip {
  background: var(--color-ink);
  border-radius: var(--radius);
  box-shadow: var(--shadow-soft);
  color: var(--color-paper);
  font-family: var(--font-body);
  font-size: 0.86rem;
  font-weight: 600;
  line-height: 1.45;
  max-width: min(22rem, 70vw);
  opacity: 0;
  padding: 0.75rem 0.85rem;
  pointer-events: none;
  position: fixed;
  transform: translateY(0.3rem);
  transition: opacity 160ms ease, transform 160ms ease;
  visibility: hidden;
  width: max-content;
  z-index: 100;
}

.term-tooltip.visible {
  opacity: 1;
  transform: translateY(0);
  visibility: visible;
}

.example-grid {
  display: grid;
  gap: var(--space-4);
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin-top: var(--space-4);
}

.example-card {
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  padding: var(--space-4);
}

.example-card h3 {
  margin-bottom: var(--space-3);
}

.compact-grid {
  display: grid;
  gap: var(--space-3);
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.compact-item {
  border-top: 1px solid var(--color-line);
  padding-top: var(--space-3);
}

.meta-strip {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-top: var(--space-4);
}

.meta-strip span {
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: 999px;
  color: var(--color-muted);
  font-size: 0.85rem;
  padding: 0.35rem 0.65rem;
}

.pill-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin: var(--space-4) 0 0;
  padding: 0;
}

.pill-list li {
  background: var(--color-paper-2);
  border: 1px solid var(--color-line);
  border-radius: 999px;
  color: var(--color-ink);
  list-style: none;
  padding: 0.45rem 0.7rem;
  white-space: nowrap;
}

.check-list,
.plain-list {
  margin: 0;
  padding-left: 1.1rem;
}

.check-list li,
.plain-list li {
  margin: 0.45rem 0;
}

.muted-note {
  color: var(--color-muted);
  font-size: 0.88rem;
  margin-top: var(--space-4);
}

.flow {
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  overflow: hidden;
}

.flow-step {
  display: grid;
  grid-template-columns: 3rem minmax(0, 1fr);
  gap: var(--space-4);
  padding: var(--space-4);
  border-top: 1px solid var(--color-line);
}

.flow-step:first-child {
  border-top: 0;
}

.flow-step span {
  align-items: center;
  background: var(--color-ink);
  border-radius: 50%;
  color: var(--color-paper);
  display: inline-flex;
  font-weight: 800;
  height: 2rem;
  justify-content: center;
  width: 2rem;
}

.mermaid-wrap {
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  margin: var(--space-5) 0;
  overflow-x: auto;
  padding: var(--space-4);
}

.source-list {
  columns: 2;
  column-gap: var(--space-7);
}

.source-list li {
  break-inside: avoid;
  margin: 0 0 var(--space-3);
}

.glossary-tools {
  display: flex;
  gap: var(--space-3);
  margin: var(--space-4) 0 var(--space-5);
}

input[type="search"] {
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  color: var(--color-ink);
  font: inherit;
  min-height: 3rem;
  padding: 0.65rem 0.8rem;
  width: min(100%, 32rem);
}

input[type="search"]:focus-visible,
button:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

.quiz-question {
  margin-bottom: var(--space-4);
}

.lesson-quiz {
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  padding: var(--space-4);
}

.lesson-quiz h2 {
  font-size: 1.35rem;
}

.quiz-options {
  display: grid;
  gap: var(--space-2);
}

.quiz-options button,
.button {
  background: var(--color-paper);
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  color: var(--color-ink);
  cursor: pointer;
  font: inherit;
  min-height: 2.75rem;
  padding: 0.75rem 0.9rem;
  text-align: left;
  transition: background 180ms ease, border-color 180ms ease, color 180ms ease;
}

.quiz-options button:hover,
.button:hover {
  background: var(--color-paper-2);
}

.quiz-options button.correct {
  background: var(--color-soft);
  border-color: var(--color-accent);
}

.quiz-options button.wrong {
  background: var(--color-danger-soft);
  border-color: var(--color-accent-2);
}

.quiz-feedback {
  color: var(--color-muted);
  min-height: 1.5rem;
  margin-top: var(--space-2);
}

.score {
  background: var(--color-ink);
  border-radius: var(--radius);
  color: var(--color-paper);
  display: inline-flex;
  font-weight: 800;
  margin-top: var(--space-4);
  padding: 0.6rem 0.8rem;
}

.site-footer {
  border-top: 1px solid var(--color-line);
  margin-top: var(--space-7);
  padding: var(--space-5) 0;
}

.footer-inner {
  color: var(--color-muted);
  display: flex;
  gap: var(--space-4);
  justify-content: space-between;
}

@media (max-width: 900px) {
  .hero,
  .lesson-layout,
  .compact-grid,
  .example-grid,
  .grid.two,
  .grid.three,
  .grid.four {
    grid-template-columns: 1fr;
  }

  .hero {
    min-height: auto;
  }

  .source-list {
    columns: 1;
  }

  .toc {
    position: static;
  }
}

@media (max-width: 640px) {
  .nav {
    align-items: flex-start;
    flex-direction: column;
  }

  .nav-links {
    justify-content: flex-start;
  }

  .nav-links a {
    font-size: 0.8rem;
    min-height: 2.35rem;
    padding: 0.66rem 0.5rem;
  }

  .hero,
  .page-head,
  .section,
  .footer-inner {
    width: min(100% - 1rem, var(--max));
  }

  .section.band > .inner {
    width: min(100% - 1rem, var(--max));
  }

  .card,
  .hero-panel {
    padding: var(--space-3);
  }

  .footer-inner {
    flex-direction: column;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
  }
}