/* ============================================================
   Summary Note – Groundwater Engineering
   Modern academic stylesheet
   ============================================================ */

:root {
  --bg: #faf9f7;
  --fg: #1e1e2e;
  --accent: #2c5282;
  --accent-soft: rgba(44,82,130,.07);
  --accent-glow: rgba(44,82,130,.14);
  --accent2: #b7791f;
  --accent2-soft: rgba(183,121,31,.08);
  --card-bg: #ffffff;
  --border: #e2e8f0;
  --border-subtle: #edf2f7;
  --note-bg: #fffbeb;
  --note-border: #f6e05e;
  --formula-bg: #ebf8ff;
  --formula-border: #90cdf4;
  --muted: #718096;
  --shadow-sm: 0 1px 3px rgba(0,0,0,.06), 0 1px 2px rgba(0,0,0,.04);
  --shadow-md: 0 4px 14px rgba(0,0,0,.07);
  --shadow-lg: 0 10px 30px rgba(0,0,0,.10);
  --radius: 12px;
  --radius-sm: 8px;
  --ease: cubic-bezier(.4,0,.2,1);
  --page-w: 880px;
}

/* ── Dark Mode ── */
[data-theme="dark"] {
  --bg: #0f1117;
  --fg: #e2e0d8;
  --accent: #63b3ed;
  --accent-soft: rgba(99,179,237,.08);
  --accent-glow: rgba(99,179,237,.15);
  --accent2: #ecc94b;
  --accent2-soft: rgba(236,201,75,.10);
  --card-bg: #1a1d27;
  --border: #2d3348;
  --border-subtle: #252a3a;
  --note-bg: #2d2a1e;
  --note-border: #b7791f;
  --formula-bg: #1a2332;
  --formula-border: #2b6cb0;
  --muted: #a0aec0;
  --shadow-sm: 0 1px 3px rgba(0,0,0,.3);
  --shadow-md: 0 4px 14px rgba(0,0,0,.35);
  --shadow-lg: 0 10px 30px rgba(0,0,0,.4);
}
[data-theme="dark"] body { background: var(--bg); color: var(--fg); }
[data-theme="dark"] svg { filter: invert(.88) hue-rotate(180deg); }
[data-theme="dark"] .page-img { border-color: var(--border); }

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

/* ── Body & Layout ── */
body {
  font-family: 'Noto Serif', 'Georgia', 'Times New Roman', serif;
  font-size: 11pt;
  line-height: 1.8;
  color: var(--fg);
  background: var(--bg);
  max-width: var(--page-w);
  margin: 0 auto;
  padding: 0 1.5rem 5rem;
  -webkit-font-smoothing: antialiased;
}

/* ── Chapter Header ── */
.ch-header {
  text-align: center;
  padding: 3rem 1.5rem 2rem;
  margin-bottom: 2rem;
  border-bottom: 1px solid var(--border);
  position: relative;
}
.ch-header .eyebrow {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 0.25rem 1rem;
  border-radius: 100px;
  margin-bottom: 0.75rem;
}
.ch-header h1 {
  font-size: 1.7rem;
  color: var(--accent);
  margin: 0;
  padding: 0;
  border: none;
  line-height: 1.3;
}
.ch-header .subtitle {
  color: var(--muted);
  font-size: 0.88rem;
  font-style: italic;
  margin-top: 0.4rem;
}

/* Legacy h1 (fallback for pages not yet updated) */
h1 {
  text-align: center;
  color: var(--accent);
  font-size: 1.7rem;
  border-bottom: 2px solid var(--border);
  padding: 2.5rem 0 0.8rem;
  margin-bottom: 1.5rem;
  line-height: 1.3;
}

/* ── Headings ── */
h2 {
  color: var(--accent);
  font-size: 1.3rem;
  margin: 2.2rem 0 0.8rem;
  padding: 0.5rem 0 0.5rem 0.9rem;
  border-left: 4px solid var(--accent2);
  background: var(--accent-soft);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}
h3 {
  font-size: 1.1rem;
  margin: 1.6rem 0 0.5rem;
  color: var(--accent);
}
h4 {
  font-size: 1rem;
  margin: 1.2rem 0 0.4rem;
  color: var(--fg);
}

/* ── Body Text ── */
p { margin: 0.6rem 0; text-align: justify; }
ul, ol { margin: 0.5rem 0 0.5rem 1.5rem; }
li { margin-bottom: 0.35rem; }
strong { color: var(--fg); }
a { color: var(--accent); text-decoration: none; transition: color .2s var(--ease); }
a:hover { color: var(--accent2); }

/* ── Tables ── */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.2rem 0;
  font-size: 0.92rem;
  border-radius: var(--radius-sm);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}
th, td {
  border: 1px solid var(--border);
  padding: 0.55rem 0.8rem;
  text-align: left;
}
th {
  background: var(--accent);
  color: #fff;
  font-weight: 700;
  font-size: 0.88rem;
  letter-spacing: 0.02em;
}
tr:nth-child(even) { background: var(--accent-soft); }
[data-theme="dark"] th { background: #2d3a50; color: #e2e0d8; }

/* ── Page Block ── */
.page-block {
  margin: 2.5rem 0;
  padding: 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card-bg);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  transition: box-shadow .3s var(--ease), border-color .3s var(--ease);
  page-break-inside: avoid;
}
.page-block:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--accent);
}

/* Page label bar */
.page-block h3 {
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin: 0;
  padding: 0.7rem 1.2rem;
  background: var(--accent-soft);
  border-bottom: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.page-block h3::before {
  content: '';
  display: inline-block;
  width: 14px;
  height: 14px;
  flex-shrink: 0;
  background: var(--accent);
  -webkit-mask-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23000' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M14 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V8z'/%3E%3Cpolyline points='14 2 14 8 20 8'/%3E%3C/svg%3E");
  mask-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23000' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M14 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V8z'/%3E%3Cpolyline points='14 2 14 8 20 8'/%3E%3C/svg%3E");
  -webkit-mask-size: contain;
  mask-size: contain;
}

/* Page image */
.page-img {
  width: 100%;
  display: block;
  cursor: pointer;
  transition: all .3s var(--ease);
  border: none;
  border-radius: 0;
}
.page-img:hover {
  opacity: 0.95;
}
.page-img.expanded {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  max-width: none;
  object-fit: contain;
  z-index: 9999;
  background: rgba(0,0,0,0.92);
  padding: 2rem;
  border-radius: 0;
  cursor: zoom-out;
}

/* ── Transcription Toggle ── */
details {
  margin: 0;
  border-top: 1px solid var(--border-subtle);
}
summary {
  cursor: pointer;
  font-weight: 700;
  font-size: 0.88rem;
  color: var(--accent);
  padding: 0.8rem 1.2rem;
  background: var(--card-bg);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: background .2s var(--ease);
  user-select: none;
  list-style: none;
}
summary::-webkit-details-marker { display: none; }
summary::before {
  content: '';
  display: inline-block;
  width: 16px;
  height: 16px;
  flex-shrink: 0;
  background: var(--accent);
  -webkit-mask-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23000' stroke-width='2'%3E%3Cpolyline points='6 9 12 15 18 9'/%3E%3C/svg%3E");
  mask-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23000' stroke-width='2'%3E%3Cpolyline points='6 9 12 15 18 9'/%3E%3C/svg%3E");
  -webkit-mask-size: contain;
  mask-size: contain;
  transition: transform .25s var(--ease);
}
details[open] > summary::before {
  transform: rotate(180deg);
}
summary:hover {
  background: var(--accent-soft);
}

.transcription {
  margin: 0;
  padding: 1.2rem 1.4rem 1.4rem;
  background: var(--card-bg);
  border-left: 3px solid var(--accent2);
  font-size: 0.93rem;
  border-radius: 0;
}

/* ── Formula & Note Boxes ── */
.formula-box {
  background: var(--formula-bg);
  border: 1px solid var(--formula-border);
  border-radius: var(--radius-sm);
  padding: 0.9rem 1.2rem;
  margin: 0.8rem 0;
  font-style: italic;
  position: relative;
}
.formula-box::before {
  content: 'f(x)';
  position: absolute;
  top: -0.5rem;
  left: 1rem;
  font-size: 0.65rem;
  font-weight: 700;
  font-style: normal;
  color: var(--accent);
  background: var(--formula-bg);
  padding: 0 0.4rem;
  letter-spacing: 0.05em;
}

.note-box {
  background: var(--note-bg);
  border: 1px solid var(--note-border);
  border-radius: var(--radius-sm);
  padding: 1rem 1.2rem;
  margin: 1rem 0;
  position: relative;
  font-size: 0.93rem;
}
.note-box::before {
  content: '';
  display: inline-block;
  width: 16px;
  height: 16px;
  vertical-align: middle;
  margin-right: 0.3rem;
  background: var(--accent2);
  -webkit-mask-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23000' stroke-width='2'%3E%3Ccircle cx='12' cy='12' r='10'/%3E%3Cline x1='12' y1='16' x2='12' y2='12'/%3E%3Cline x1='12' y1='8' x2='12.01' y2='8'/%3E%3C/svg%3E");
  mask-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23000' stroke-width='2'%3E%3Ccircle cx='12' cy='12' r='10'/%3E%3Cline x1='12' y1='16' x2='12' y2='12'/%3E%3Cline x1='12' y1='8' x2='12.01' y2='8'/%3E%3C/svg%3E");
  -webkit-mask-size: contain;
  mask-size: contain;
}

/* ── Navigation Links ── */
.nav-links {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin: 0.5rem 0 1rem;
  padding: 0.8rem 0;
  gap: 1rem;
}
.nav-links a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 700;
  font-size: 0.88rem;
  padding: 0.5rem 1.2rem;
  border: 1.5px solid var(--border);
  border-radius: 100px;
  transition: all .25s var(--ease);
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background: var(--card-bg);
  box-shadow: var(--shadow-sm);
  white-space: nowrap;
}
.nav-links a:hover {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
  box-shadow: var(--shadow-md);
  transform: translateY(-1px);
}

/* ── Index Page Styles ── */
.index-hero {
  text-align: center;
  padding: 3.5rem 1rem 2.5rem;
  margin-bottom: 2rem;
}
.index-hero h1 {
  font-size: 2rem;
  border: none;
  padding: 0;
  margin: 0 0 0.5rem;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.index-hero .tagline {
  color: var(--muted);
  font-style: italic;
  font-size: 0.95rem;
}

.chapter-grid {
  display: grid;
  gap: 0.8rem;
  margin: 1.5rem 0 2rem;
}
.chapter-card {
  display: flex;
  align-items: stretch;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card-bg);
  text-decoration: none;
  color: var(--fg);
  overflow: hidden;
  transition: all .3s var(--ease);
  box-shadow: var(--shadow-sm);
}
.chapter-card:hover {
  border-color: var(--accent);
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  color: var(--fg);
}
.chapter-card .card-num {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 56px;
  background: var(--accent);
  color: #fff;
  font-weight: 800;
  font-size: 1.1rem;
  letter-spacing: -0.02em;
}
.chapter-card .card-body {
  padding: 0.9rem 1.1rem;
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.chapter-card .card-title {
  font-weight: 700;
  font-size: 0.95rem;
  line-height: 1.3;
  color: var(--fg);
}
.chapter-card .card-pages {
  font-size: 0.78rem;
  color: var(--muted);
  margin-top: 0.2rem;
}
.chapter-card .card-arrow {
  display: flex;
  align-items: center;
  padding: 0 1rem;
  color: var(--muted);
  font-size: 1.2rem;
  transition: transform .25s var(--ease), color .25s var(--ease);
}
.chapter-card:hover .card-arrow {
  color: var(--accent);
  transform: translateX(3px);
}

/* ── Keyboard Shortcut Badge ── */
kbd {
  display: inline-block;
  padding: 0.1rem 0.45rem;
  font-family: 'SF Mono', 'Consolas', monospace;
  font-size: 0.78rem;
  color: var(--fg);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 4px;
  box-shadow: 0 1px 0 var(--border);
  line-height: 1.4;
}

/* ── Figures ── */
figure {
  text-align: center;
  margin: 1.5rem auto;
}
figcaption {
  font-size: 0.82rem;
  color: var(--muted);
  margin-top: 0.4rem;
  font-style: italic;
}

/* ── Back Link ── */
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.85rem;
  color: var(--muted);
  text-decoration: none;
  padding: 0.5rem 0;
  transition: color .2s var(--ease);
}
.back-link:hover { color: var(--accent); }

/* ── Print ── */
@media print {
  .theme-toggle, .nav-links, .cm-scroll-progress,
  .cm-dark-toggle, .cm-fab-annotate, .back-link { display: none !important; }
  .page-block { break-inside: avoid; border: 1px solid #ccc; box-shadow: none; }
  body { max-width: 100%; padding: 1rem; background: #fff; color: #000; }
  h1, h2, h3 { color: #111; }
  .transcription { border-left-color: #999; }
}

/* ── Mobile ── */
@media (max-width: 640px) {
  body { padding: 0 1rem 5rem; }
  h1 { font-size: 1.3rem; padding-top: 1.8rem; }
  .ch-header { padding: 2rem 0.5rem 1.5rem; }
  .ch-header h1 { font-size: 1.3rem; }
  h2 { font-size: 1.1rem; }
  table { font-size: 0.78rem; }
  .nav-links a { font-size: 0.8rem; padding: 0.4rem 0.8rem; }
  .page-block h3 { padding: 0.6rem 1rem; font-size: 0.78rem; }
  .transcription { padding: 1rem; }
  .chapter-card .card-num { min-width: 44px; font-size: 0.95rem; }
  .chapter-card .card-body { padding: 0.7rem 0.9rem; }
  .chapter-card .card-title { font-size: 0.88rem; }
  .index-hero h1 { font-size: 1.5rem; }
}