/* ============================================================
   Structure – Unified Textbook Stylesheet
   Clean academic formatting with modern touches
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');

:root {
  --base: 12pt;
  --ink: #111;
  --muted: #666;
  --line: #e5e7eb;
  --soft: #f8f9fa;
  --page-w: 820px;
  --ease: cubic-bezier(.4,0,.2,1);
  --accent: #4f46e5;
  --accent-soft: rgba(79,70,229,.06);
  --accent-glow: rgba(79,70,229,.12);
  --radius: 12px;
  --radius-sm: 8px;
}

/* ── Dark Mode ── */
[data-theme="dark"] {
  --ink: #e0ddd5;
  --muted: #9ca3af;
  --line: #2a2d35;
  --soft: #1a1d24;
  --accent: #818cf8;
  --accent-soft: rgba(129,140,248,.08);
  --accent-glow: rgba(129,140,248,.15);
}
[data-theme="dark"] body {
  background: #0f1015 !important;
  color: var(--ink);
}
[data-theme="dark"] h1, [data-theme="dark"] h2 {
  border-color: #333;
}
[data-theme="dark"] th {
  background: #1f2128;
  color: #e0ddd5;
}
[data-theme="dark"] td {
  background: transparent;
}
[data-theme="dark"] table {
  border-color: var(--line);
}
[data-theme="dark"] th, [data-theme="dark"] td {
  border-color: var(--line);
}
[data-theme="dark"] .exam-note {
  border-color: var(--line);
  background: var(--soft);
}
[data-theme="dark"] .callout {
  border-color: var(--accent);
  background: var(--accent-soft);
}
[data-theme="dark"] .figure-container {
  border-color: var(--line);
}
[data-theme="dark"] pre, [data-theme="dark"] code {
  background: var(--soft);
}
[data-theme="dark"] .print-btn {
  background: rgba(20,20,30,.8);
  color: var(--ink);
  border-color: var(--line);
}
[data-theme="dark"] svg text {
  fill: var(--ink);
}

/* ── Reset ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

/* ── Body ── */
body {
  font-family: 'Times New Roman', Times, serif;
  font-size: var(--base);
  color: var(--ink);
  background: #fafafa;
  line-height: 1.7;
  max-width: var(--page-w);
  margin: 0 auto;
  padding: 2rem 2.5rem 4rem;
  -webkit-font-smoothing: antialiased;
  transition: background .3s var(--ease), color .3s var(--ease);
}

/* ── Topbar Nav ── */
.topbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 9990;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 24px;
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  font-size: 13px;
  background: rgba(255,255,255,.78);
  backdrop-filter: blur(16px) saturate(180%);
  -webkit-backdrop-filter: blur(16px) saturate(180%);
  border-bottom: 1px solid rgba(0,0,0,.06);
  transition: background .3s, border-color .3s;
}
.topbar a {
  text-decoration: none;
  color: var(--ink);
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 5px 12px;
  border-radius: var(--radius-sm);
  transition: all .2s var(--ease);
  font-weight: 600;
}
.topbar a:hover {
  background: var(--accent-soft);
  color: var(--accent);
}
.topbar span {
  color: var(--muted);
  font-weight: 400;
}
[data-theme="dark"] .topbar {
  background: rgba(15,16,21,.78);
  border-color: rgba(255,255,255,.05);
}
body:has(.topbar) {
  padding-top: calc(2rem + 44px);
}

/* ── Chapter Header ── */
.ch-header {
  text-align: center;
  padding: 2.5rem 0 2rem;
  margin-bottom: 2rem;
  border-bottom: 2px solid var(--line);
  animation: ch-fade-in .6s var(--ease) both;
}
@keyframes ch-fade-in {
  from { opacity: 0; transform: translateY(18px); }
  to   { opacity: 1; transform: translateY(0); }
}
.ch-header h1 {
  font-size: 18pt;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 0.6rem;
  padding-bottom: 0;
  border-bottom: none;
  background: linear-gradient(135deg, var(--ink) 0%, var(--muted) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
[data-theme="dark"] .ch-header h1 {
  background: linear-gradient(135deg, #fff 0%, #a1a1aa 100%);
  -webkit-background-clip: text;
  background-clip: text;
}
.ch-header .meta {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 11pt;
  color: var(--accent);
  font-weight: 500;
  letter-spacing: 0.02em;
  margin-bottom: 0.5rem;
}
.ch-header .author {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 10pt;
  color: var(--muted);
  font-weight: 400;
  font-style: italic;
}

/* ── TOC Card ── */
.toc-card {
  background: var(--soft);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.4rem 1.6rem;
  margin: 1.5rem 0 2rem;
  animation: ch-fade-in .6s var(--ease) .1s both;
}
.toc-card h3 {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 11pt;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  margin-bottom: 0.8rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--line);
}
.toc-grid {
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.toc-grid a {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 10.5pt;
  color: var(--ink);
  text-decoration: none;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  transition: all .2s var(--ease);
  display: block;
}
.toc-grid a:hover {
  background: var(--accent-soft);
  color: var(--accent);
  padding-left: 18px;
}
[data-theme="dark"] .toc-card {
  background: var(--soft);
  border-color: var(--line);
}

/* ── Content wrapper ── */
.content {
  animation: ch-fade-in .6s var(--ease) .2s both;
}

/* ── SVG Wrapper ── */
.svg-wrap {
  text-align: center;
  margin: 2rem 0;
  padding: 1.2rem;
  background: var(--soft);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow-x: auto;
  break-inside: avoid;
}
[data-theme="dark"] .svg-wrap {
  background: var(--soft);
  border-color: var(--line);
}

/* ── Headings ── */
h1, h2, h3, h4, h5, h6 {
  font-family: 'Times New Roman', Times, serif;
  color: var(--ink);
  line-height: 1.3;
}

h1 {
  font-size: 16pt;
  font-weight: 800;
  text-transform: uppercase;
  text-align: center;
  margin: 0 0 1.5rem;
  padding-bottom: 0.6rem;
  border-bottom: 2px solid var(--line);
  letter-spacing: 0.03em;
}

h2 {
  font-size: 13pt;
  font-weight: 700;
  text-transform: uppercase;
  margin: 2.5rem 0 1rem;
  padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--line);
  letter-spacing: 0.02em;
  position: relative;
}
h2::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 0;
  width: 40px;
  height: 2px;
  background: var(--accent);
  border-radius: 1px;
}

h3 {
  font-size: 12pt;
  font-weight: 700;
  margin: 1.8rem 0 0.6rem;
  padding-left: 0.8rem;
  border-left: 3px solid var(--accent);
}

h4 {
  font-size: 12pt;
  font-weight: 700;
  font-style: italic;
  margin: 1.2rem 0 0.5rem;
}

h5 {
  font-size: 11pt;
  font-weight: 600;
  margin: 1rem 0 0.4rem;
}

/* ── Body text ── */
p {
  font-size: var(--base);
  text-align: justify;
  margin: 0 0 1rem;
  hyphens: auto;
}

/* Book-style indent for consecutive paragraphs */
p + p {
  text-indent: 1.5em;
}

/* ── Lists ── */
ul, ol {
  margin: 0.5rem 0 1rem;
  padding-left: 2rem;
}

li {
  font-size: var(--base);
  text-align: justify;
  margin-bottom: 0.5rem;
  line-height: 1.6;
}

ul > li { list-style-type: disc; }
ul > li > ul > li { list-style-type: circle; }

/* ── Equations ── */
.equation {
  display: flex;
  justify-content: center;
  align-items: center;
  margin: 1.5rem 0;
  overflow-x: auto;
}

/* ── Exam note boxes ── */
.exam-note {
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius-sm);
  padding: 1.2rem 1.4rem;
  margin: 1.5rem 0;
  background: var(--accent-soft);
  break-inside: avoid;
  transition: border-color .2s var(--ease);
}

.exam-note h4 {
  margin-top: 0;
  border-bottom: 1px dashed var(--line);
  padding-bottom: 0.3rem;
  color: var(--accent);
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 10.5pt;
}

/* ── Callout boxes ── */
.callout {
  border-left: 3px solid var(--accent);
  padding: 1rem 1.2rem 1rem 1.4rem;
  margin: 1.5rem 0;
  font-style: italic;
  background: var(--soft);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}

/* ── Blockquote ── */
blockquote {
  border-left: 3px solid var(--line);
  padding: 1rem 1.2rem 1rem 1.4rem;
  margin: 1.5rem 0;
  font-style: italic;
  color: var(--muted);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  background: var(--soft);
}

/* ── Tables ── */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  font-size: var(--base);
  border-radius: var(--radius-sm);
  overflow: hidden;
  border: 1px solid var(--line);
}

table.info-table { /* alias used in some files */ }

th, td {
  border: 1px solid var(--line);
  padding: 10px 14px;
  text-align: left;
  vertical-align: top;
  font-size: var(--base);
}

th {
  font-weight: 700;
  background: var(--soft);
  text-transform: uppercase;
  font-size: 10.5pt;
  font-family: 'Inter', system-ui, sans-serif;
  letter-spacing: 0.04em;
  color: var(--muted);
}

caption {
  caption-side: bottom;
  font-style: italic;
  color: var(--muted);
  font-size: 10pt;
  padding-top: 0.4rem;
}

/* ── Figures ── */
.figure-container, figure {
  text-align: center;
  margin: 2rem 0;
  padding: 1.2rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--soft);
  break-inside: avoid;
  transition: border-color .2s var(--ease);
}
.figure-container:hover, figure:hover {
  border-color: var(--accent-glow);
}

.figcaption, figcaption {
  font-style: italic;
  margin-top: 0.5rem;
  text-align: center;
  font-size: 10pt;
  color: var(--muted);
}

svg {
  max-width: 100%;
  height: auto;
  display: block;
  margin: 0 auto;
}

/* ── Images ── */
img {
  max-width: 100%;
  height: auto;
  display: block;
  margin: 1rem auto;
}

/* ── Code ── */
code {
  font-family: 'Consolas', 'Monaco', monospace;
  background: var(--soft);
  padding: 1px 5px;
  border: 0.5px solid var(--line);
  font-size: 10pt;
}

pre {
  background: var(--soft);
  padding: 1rem;
  border-left: 3px solid var(--ink);
  overflow-x: auto;
  margin: 1rem 0;
  line-height: 1.5;
}

pre code {
  background: none;
  border: none;
  padding: 0;
}

/* ── Print button ── */
.print-btn {
  position: fixed;
  top: 12px;
  right: 68px;
  border: 1px solid rgba(0,0,0,.08);
  background: rgba(255,255,255,.8);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  color: var(--ink);
  padding: 8px 16px;
  font-weight: 600;
  cursor: pointer;
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 11px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  border-radius: var(--radius-sm);
  z-index: 9995;
  transition: all .25s var(--ease);
}

.print-btn:hover {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
  box-shadow: 0 4px 12px rgba(79,70,229,.25);
}

/* ── Links ── */
a {
  color: var(--accent);
  text-decoration: none;
  text-underline-offset: 3px;
  transition: color .2s var(--ease);
}

a:hover {
  text-decoration: underline;
  text-decoration-thickness: 1.5px;
}

/* ── Horizontal rule ── */
hr {
  border: none;
  border-top: 1px solid var(--line);
  margin: 2rem 0;
}

/* ── Strong / emphasis ── */
strong, b { font-weight: 700; }
em, i { font-style: italic; }

/* ── MathJax overrides ── */
mjx-container[jax="CHTML"]:not([display="true"]) {
  display: inline !important;
  overflow-x: visible !important;
}
mjx-container, .MathJax, .MathJax_Display {
  overflow-x: auto;
  overflow-y: hidden;
  max-width: 100%;
}

/* ── Example / Question Card ── */
.example {
  margin: 2.5rem 0;
  padding: 0;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  break-inside: avoid;
  background: var(--bg, #fff);
}
[data-theme="dark"] .example {
  background: var(--soft);
  border-color: var(--line);
}
.ex-title {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 10.5pt;
  font-weight: 600;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 0.6rem 1.4rem;
  border-bottom: 1px solid var(--line);
  letter-spacing: 0.02em;
}
.ex-q {
  padding: 1rem 1.4rem;
  font-size: var(--base);
  line-height: 1.8;
  text-align: justify;
}

/* ── Equation Block ── */
.eq-block {
  display: block;
  text-align: center;
  margin: 1.2rem 0;
  padding: 0.6rem 1rem;
  overflow-x: auto;
}
.eq-block.hl {
  background: var(--accent-soft);
  border: 1px solid var(--accent-glow);
  border-radius: var(--radius-sm);
  padding: 1rem 1.2rem;
  margin: 1.5rem 0;
}
[data-theme="dark"] .eq-block.hl {
  background: var(--accent-soft);
  border-color: var(--accent-glow);
}

/* ── Definition Box ── */
.def-box {
  border: 1px solid var(--line);
  border-left: 4px solid var(--accent);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 1.2rem 1.4rem;
  margin: 1.5rem 0;
  background: var(--soft);
  break-inside: avoid;
}
.def-box .dt,
.dt {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 11pt;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 0.6rem;
  padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--line);
}
[data-theme="dark"] .def-box {
  background: var(--soft);
  border-color: var(--line);
  border-left-color: var(--accent);
}

/* ── Note Box ── */
.note {
  border: 1px solid var(--line);
  border-left: 3px solid #d97706;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 0.8rem 1.2rem;
  margin: 1rem 0;
  background: rgba(217,119,6,.04);
  font-size: 11pt;
  line-height: 1.6;
}
[data-theme="dark"] .note {
  background: rgba(217,119,6,.06);
  border-color: var(--line);
  border-left-color: #f59e0b;
}

/* ── Result / Answer Box ── */
.result-box {
  text-align: center;
  margin: 1.5rem 0;
  padding: 1rem 1.2rem;
  background: linear-gradient(135deg, rgba(16,185,129,.05) 0%, rgba(5,150,105,.08) 100%);
  border: 1px solid rgba(16,185,129,.2);
  border-radius: var(--radius-sm);
  overflow-x: auto;
}
[data-theme="dark"] .result-box {
  background: rgba(16,185,129,.06);
  border-color: rgba(16,185,129,.15);
}

/* ── Solution Label ── */
.soln-label {
  display: inline-block;
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 10pt;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: #fff;
  background: var(--accent);
  padding: 4px 16px;
  border-radius: 4px;
  margin: 1.5rem 0 1rem;
}

/* ── Figure Caption ── */
.fig-caption {
  font-style: italic;
  text-align: center;
  font-size: 10pt;
  color: var(--muted);
  margin: -0.5rem 0 1.5rem;
}

/* ── Step Box ── */
.step-box {
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 1rem 1.2rem;
  margin: 1rem 0;
  background: var(--soft);
  break-inside: avoid;
}

/* ── Formula Card ── */
.formula-card,
.quick-formulas {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.2rem 1.4rem;
  margin: 1.5rem 0;
  background: var(--soft);
  break-inside: avoid;
}

/* ── Summary Table ── */
.summary-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  font-size: var(--base);
}

/* ── Matrix Table ── */
.matrix-table {
  border-collapse: collapse;
  margin: 1rem auto;
  font-size: 10pt;
}
.matrix-table th,
.matrix-table td {
  padding: 6px 10px;
  text-align: center;
  border: 1px solid var(--line);
}

/* ── Visual Grid ── */
.visual-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 16px;
  margin: 1.5rem 0;
}
.visual-card,
.band-card,
.hero-card,
.hero-panel {
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 1rem 1.2rem;
  background: var(--soft);
  break-inside: avoid;
}
[data-theme="dark"] .visual-card,
[data-theme="dark"] .band-card,
[data-theme="dark"] .hero-card,
[data-theme="dark"] .hero-panel {
  background: var(--soft);
  border-color: var(--line);
}

/* ── Mini Grid ── */
.mini-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 12px;
  margin: 1rem 0;
}
.mini-note {
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 0.7rem 1rem;
  background: var(--soft);
  font-size: 11pt;
}

/* ── Chips / Tags ── */
.chip-row {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin: 0.5rem 0;
}
.chip {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 9pt;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 20px;
  background: var(--accent-soft);
  color: var(--accent);
  white-space: nowrap;
}

/* ── Code Block ── */
.code-block {
  background: var(--soft);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 1rem;
  overflow-x: auto;
  font-family: 'Consolas', 'Monaco', monospace;
  font-size: 10pt;
  line-height: 1.5;
  margin: 1rem 0;
}

/* ── Chapter Band ── */
.chapter-band {
  background: var(--accent-soft);
  border: 1px solid var(--accent-glow);
  border-radius: var(--radius-sm);
  padding: 1rem 1.2rem;
  margin: 1rem 0;
}

/* ── Pattern (decorative) ── */
.pattern {
  opacity: 0.06;
  pointer-events: none;
}

/* ── Back to Top ── */
.btt {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 11px;
  color: var(--accent);
  text-decoration: none;
  padding: 6px 14px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--accent-glow);
  margin: 1.5rem 0;
  transition: all .2s var(--ease);
}
.btt:hover {
  background: var(--accent-soft);
}

/* ── Next link ── */
.next {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 11pt;
  color: var(--accent);
  text-decoration: none;
  padding: 8px 16px;
  border: 1px solid var(--accent-glow);
  border-radius: var(--radius-sm);
  margin: 1.5rem 0;
  transition: all .2s var(--ease);
}
.next:hover {
  background: var(--accent-soft);
}

/* ── Question Index (inline styles override) ── */
.qi-container {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.2rem 1.5rem;
  margin: 1.5rem 0 2rem;
}
.qi-container h2,
.qi-container h3 {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 11pt;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin: 0 0 0.8rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--line);
  color: var(--muted);
}
.qi-container h2::after {
  display: none;
}
.qi-grid {
  display: flex;
  flex-direction: column;
  gap: 0;
}
.qi-item {
  display: flex;
  align-items: baseline;
  gap: 0.8rem;
  padding: 0.5rem 0.6rem;
  border-bottom: 1px dotted var(--line);
  text-decoration: none;
  color: var(--ink);
  border-radius: var(--radius-sm);
  transition: all .15s var(--ease);
}
.qi-item:last-child {
  border-bottom: none;
}
.qi-item:hover {
  background: var(--accent-soft);
  color: var(--accent);
}
.qi-num {
  font-weight: 700;
  min-width: 2.5rem;
  flex-shrink: 0;
  color: var(--accent);
}
.qi-title {
  flex: 1;
}
.qi-meta {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 9pt;
  color: var(--muted);
  font-style: italic;
  white-space: nowrap;
  background: var(--soft);
  padding: 2px 8px;
  border-radius: 4px;
}
[data-theme="dark"] .qi-container {
  border-color: var(--line);
}
[data-theme="dark"] .qi-item {
  color: var(--ink);
  border-color: var(--line);
}
[data-theme="dark"] .qi-item:hover {
  background: var(--accent-soft);
}

/* ── Scrollbar ── */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
  background: var(--line);
  border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover { background: var(--muted); }

/* ── Print styles ── */
@media print {
  body {
    padding: 0;
    max-width: 100%;
    background: white;
    color: black;
  }
  .print-btn, .cm-dm-toggle, .cm-nav-bar, .topbar,
  .dw-btn, .dw-tb, .dw-cv, .cm-scroll-progress, .cm-scroll-top {
    display: none !important;
  }
  h1, h2, h3 { page-break-after: avoid; }
  .figure-container, figure, .exam-note, .callout, table {
    page-break-inside: avoid;
  }
  h2::after { display: none; }
}

/* ── Responsive ── */
@media (max-width: 600px) {
  body {
    padding: 1rem;
    font-size: 11pt;
  }
  h1 { font-size: 14pt; }
  h2 { font-size: 12pt; }
  .topbar { padding: 8px 12px; font-size: 12px; }
  .toc-card { padding: 1rem; }
  .ch-header { padding: 1.5rem 0 1rem; }
}