@import url('https://fonts.googleapis.com/css2?family=Newsreader:ital,opsz,wght@0,6..72,300;0,6..72,400;0,6..72,500;0,6..72,700;1,6..72,400;1,6..72,500&family=IBM+Plex+Mono:wght@400;500;700&family=IBM+Plex+Sans:wght@400;500;600&display=swap');

:root {
  --paper:        #f4f1ea;
  --paper-dark:   #e8e3d6;
  --paper-darker: #ddd5c4;
  --ink:          #1a1612;
  --ink-soft:     #3d3832;
  --ink-faded:    #6b6257;
  --ink-ghost:    #a39886;
  --rust:         #1f4e79;
  --rust-dark:    #163758;
  --blue:         #7a4a2d;
  --green:        #3d6b3a;
  --ochre:        #c68a1f;
  --line:         #c9c0ae;
  --line-soft:    #ddd5c4;
  --serif:        'Newsreader', Georgia, serif;
  --mono:         'IBM Plex Mono', Menlo, monospace;
  --sans:         'IBM Plex Sans', system-ui, sans-serif;
  --packet-hl:    #e6edf6;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 18px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  position: relative;
  min-height: 100vh;
}

body::before {
  content: '';
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 1;
  opacity: 0.35;
  mix-blend-mode: multiply;
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='240' height='240'><filter id='n'><feTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='2' stitchTiles='stitch'/><feColorMatrix values='0 0 0 0 0.6  0 0 0 0 0.55  0 0 0 0 0.45  0 0 0 0.18 0'/></filter><rect width='100%' height='100%' filter='url(%23n)'/></svg>");
}

a { color: var(--rust); text-decoration: none; border-bottom: 1px solid rgba(31, 78, 121, 0.25); transition: color .15s, border-color .15s; }
a:hover { color: var(--rust-dark); border-color: var(--rust-dark); }

h1, h2, h3, h4 { font-family: var(--serif); font-weight: 500; color: var(--ink); letter-spacing: -0.01em; }
h1 { font-size: 3.4rem; line-height: 1.05; margin: 0 0 1rem; }
h1 em { font-style: italic; color: var(--rust); font-weight: 400; }
h2 { font-size: 2rem; line-height: 1.2; margin: 2.2rem 0 1rem; }
h2 em { font-style: italic; color: var(--rust); font-weight: 400; }
h3 { font-size: 1.4rem; margin: 1.8rem 0 .6rem; }
h4 { font-size: 1.1rem; margin: 1.4rem 0 .4rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--ink-faded); font-family: var(--mono); font-weight: 500; }

p { margin: 0 0 1rem; }
em { font-style: italic; }
strong { font-weight: 600; color: var(--ink); }
hr { border: none; border-top: 1px solid var(--line-soft); margin: 2rem 0; }

code { font-family: var(--mono); font-size: 0.92em; background: var(--paper-dark); padding: 0.1em 0.35em; border-radius: 3px; }
pre { font-family: var(--mono); font-size: 0.88rem; background: var(--paper-dark); border: 1px solid var(--line-soft); border-radius: 4px; padding: 1rem 1.2rem; overflow-x: auto; line-height: 1.55; margin: 1.2rem 0; }
pre code { background: none; padding: 0; }

ul, ol { padding-left: 1.4rem; }
li { margin-bottom: 0.4rem; }

.container { max-width: 820px; margin: 0 auto; padding: 0 32px; position: relative; z-index: 2; }
.container.wide, .container-wide { max-width: 1000px; }

/* ─────────────────────────── Top nav ─────────────────────────── */
.site-nav {
  position: sticky;
  top: 0;
  background: rgba(244, 241, 234, 0.92);
  backdrop-filter: blur(6px);
  -webkit-backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--line-soft);
  z-index: 50;
  padding: 14px 0;
}
.site-nav .container { display: flex; align-items: center; gap: 24px; }
.site-nav .brand { font-family: var(--mono); font-size: 0.95rem; font-weight: 700; letter-spacing: 0.08em; color: var(--ink); border: none; }
.site-nav .nav-back { font-family: var(--sans); font-size: 0.9rem; color: var(--ink-faded); border: none; }
.site-nav .nav-back:hover { color: var(--rust); }

.nav-search-wrapper { position: relative; margin-left: auto; flex: 0 1 320px; }
.nav-search-icon { position: absolute; left: 10px; top: 50%; transform: translateY(-50%); width: 16px; height: 16px; color: var(--ink-faded); pointer-events: none; }
#nav-search {
  width: 100%;
  font-family: var(--sans);
  font-size: 0.9rem;
  padding: 8px 12px 8px 34px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--paper);
  color: var(--ink);
}
#nav-search:focus { outline: none; border-color: var(--rust); }
#nav-search:disabled { opacity: 0.5; cursor: wait; }

#nav-search-results {
  position: absolute;
  top: calc(100% + 6px);
  left: 0;
  right: 0;
  max-height: 60vh;
  overflow-y: auto;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 6px;
  box-shadow: 0 12px 32px rgba(0,0,0,0.10);
  display: none;
}
#nav-search-results.open { display: block; }
.nav-sr-item { display: block; padding: 10px 14px; border: none; border-bottom: 1px solid var(--line-soft); cursor: pointer; }
.nav-sr-item:last-child { border-bottom: none; }
.nav-sr-item:hover, .nav-sr-active { background: var(--paper-dark); }
.nav-sr-chapter { font-family: var(--mono); font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.07em; color: var(--ink-faded); }
.nav-sr-title { font-family: var(--serif); font-size: 1rem; color: var(--ink); margin: 2px 0 4px; }
.nav-sr-body { font-size: 0.85rem; color: var(--ink-soft); line-height: 1.5; }
.nav-sr-body mark { background: rgba(31, 78, 121, 0.2); color: var(--ink); padding: 0 2px; border-radius: 2px; }
.nav-sr-empty { padding: 14px; color: var(--ink-faded); font-style: italic; text-align: center; }

/* ─────────────────────────── Hero ─────────────────────────── */
.hero { padding: 4rem 0 2.5rem; }
.eyebrow { font-family: var(--mono); font-size: 0.78rem; letter-spacing: 0.18em; text-transform: uppercase; color: var(--ink-faded); margin-bottom: 1rem; }
.lede { font-family: var(--serif); font-size: 1.35rem; line-height: 1.55; font-style: italic; color: var(--ink-soft); max-width: 38em; margin-top: 1rem; }

/* ─────────────────────────── ToCs ─────────────────────────── */
.toc { display: flex; flex-wrap: wrap; gap: 0.6rem 1.4rem; margin: 1.8rem 0 0; padding: 0; list-style: none; }
.toc a { display: inline-flex; align-items: baseline; gap: 0.5rem; font-size: 0.95rem; color: var(--ink-soft); border: none; padding: 4px 0; }
.toc a:hover { color: var(--rust); }
.toc a span { font-family: var(--mono); font-size: 0.75rem; color: var(--ink-faded); }

.chapter-toc { padding: 1.5rem 0; border-bottom: 1px solid var(--line-soft); background: var(--paper-dark); }
.chapter-toc-list { display: flex; flex-wrap: wrap; gap: 1.4rem 2rem; padding: 0; list-style: none; margin: 0; }
.chapter-toc-list li { display: flex; align-items: baseline; gap: 0.6rem; margin: 0; }
.chapter-toc-list a { font-family: var(--serif); font-size: 1rem; color: var(--ink-soft); border: none; }
.chapter-toc-list a:hover { color: var(--rust); }
.toc-num { font-family: var(--mono); font-size: 0.75rem; color: var(--ink-faded); letter-spacing: 0.06em; }

/* ─────────────────────────── Sections ─────────────────────────── */
section { padding: 3rem 0; border-top: 1px solid var(--line-soft); }
section:first-of-type { border-top: none; }

.section-badge {
  display: inline-block;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--rust);
  background: rgba(31, 78, 121, 0.10);
  padding: 4px 10px;
  border-radius: 12px;
  margin-bottom: 0.8rem;
}

.section-intro { font-style: italic; font-size: 1.15rem; color: var(--ink-faded); max-width: 36em; margin-bottom: 1.4rem; }

.dropcap::first-letter {
  initial-letter: 3;
  -webkit-initial-letter: 3;
  font-family: var(--serif);
  font-weight: 500;
  color: var(--rust);
  margin-right: 0.1em;
  font-size: 3.4em;
  float: left;
  line-height: 0.9;
  padding: 0.05em 0.08em 0 0;
}

/* ─────────────────────────── Callouts ─────────────────────────── */
.callout {
  background: rgba(31, 78, 121, 0.06);
  border-left: 3px solid var(--rust);
  padding: 1rem 1.2rem;
  margin: 1.4rem 0;
  border-radius: 0 4px 4px 0;
}
.callout-blue {
  background: rgba(122, 74, 45, 0.06);
  border-left-color: var(--blue);
}
.callout .label {
  display: block;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--rust);
  margin-bottom: 0.4rem;
}
.callout-blue .label { color: var(--blue); }
.callout p:last-child { margin-bottom: 0; }

/* ─────────────────────────── Quiz ─────────────────────────── */
.quiz {
  background: var(--paper-dark);
  border: 1px solid var(--line-soft);
  border-radius: 6px;
  padding: 1.2rem 1.4rem;
  margin: 1.2rem 0;
}
.q-label {
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-faded);
  margin-bottom: 0.5rem;
}
.q-text { font-size: 1.05rem; color: var(--ink); margin-bottom: 0.8rem; }
.quiz-reveal { margin-top: 0.8rem; }
.reveal-btn {
  font-family: var(--sans);
  font-size: 0.9rem;
  background: var(--rust);
  color: var(--paper);
  border: none;
  padding: 8px 16px;
  border-radius: 18px;
  cursor: pointer;
  transition: background .15s;
}
.reveal-btn:hover { background: var(--rust-dark); }
.reveal-btn.used { background: var(--ink-ghost); cursor: default; }
.answer {
  display: none;
  margin-top: 0.8rem;
  padding: 0.8rem 1rem;
  background: var(--paper);
  border-left: 3px solid var(--green);
  border-radius: 0 4px 4px 0;
  color: var(--ink-soft);
}
.answer.show { display: block; }

/* ─────────────────────────── Interactive quiz (MCQ) ─────────────────────────── */
.quiz.mcq .q-text { margin-bottom: 1rem; }
.mcq-options { list-style: none; padding: 0; margin: 0 0 0.8rem; display: flex; flex-direction: column; gap: 0.5rem; }
.mcq-options li { margin: 0; }
.mcq-opt {
  width: 100%;
  text-align: left;
  font-family: var(--serif);
  font-size: 1rem;
  background: var(--paper);
  color: var(--ink);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 0.7rem 0.9rem 0.7rem 2.4rem;
  position: relative;
  cursor: pointer;
  transition: background .15s, border-color .15s;
}
.mcq-opt::before {
  content: attr(data-letter);
  position: absolute;
  left: 0.9rem;
  top: 50%;
  transform: translateY(-50%);
  font-family: var(--mono);
  font-size: 0.78rem;
  color: var(--ink-faded);
  letter-spacing: 0.06em;
}
.mcq-opt:hover { background: var(--paper-dark); border-color: var(--rust); }
.mcq-opt.correct { background: rgba(61, 107, 58, 0.15); border-color: var(--green); color: var(--ink); }
.mcq-opt.correct::before { color: var(--green); }
.mcq-opt.wrong { background: rgba(168, 60, 50, 0.10); border-color: #a83c32; color: var(--ink-soft); }
.mcq-opt.wrong::before { color: #a83c32; }
.mcq-opt.locked { cursor: default; }
.mcq-feedback {
  display: none;
  margin-top: 0.6rem;
  padding: 0.7rem 0.9rem;
  background: var(--paper);
  border-left: 3px solid var(--green);
  border-radius: 0 4px 4px 0;
  font-size: 0.95rem;
  color: var(--ink-soft);
}
.mcq-feedback.show { display: block; }
.mcq-feedback.wrong { border-left-color: #a83c32; }

/* ─────────────────────────── Code + result panes ─────────────────────────── */
.code-result { display: grid; grid-template-columns: 1fr; gap: 0.8rem; margin: 1.4rem 0; }
@media (min-width: 760px) { .code-result.two-col { grid-template-columns: 1fr 1fr; gap: 1rem; } }
.code-result figure, .code-result .pane { margin: 0; }
.pane-label {
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-faded);
  margin-bottom: 0.4rem;
}
.code-result pre { margin: 0; }
.code-result table { font-size: 0.86rem; }
.code-result table th, .code-result table td { padding: 0.4rem 0.7rem; }
.code-result .pane.result {
  background: var(--paper-dark);
  border: 1px solid var(--line-soft);
  border-radius: 4px;
  padding: 0.8rem 1rem;
  overflow-x: auto;
}

/* SQL syntax (light theme) */
.sql-kw  { color: var(--rust); font-weight: 600; }
.sql-fn  { color: var(--blue); }
.sql-str { color: var(--green); }
.sql-num { color: var(--ochre); }
.sql-com { color: var(--ink-ghost); font-style: italic; }

/* ─────────────────────────── Inline tag / pill ─────────────────────────── */
.pill {
  display: inline-block;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  padding: 2px 8px;
  border-radius: 10px;
  background: var(--paper-dark);
  border: 1px solid var(--line-soft);
  color: var(--ink-soft);
  margin-right: 4px;
}
.pill.rust  { background: rgba(31, 78, 121, 0.10); color: var(--rust); border-color: transparent; }
.pill.green { background: rgba(61, 107, 58, 0.12); color: var(--green); border-color: transparent; }
.pill.blue  { background: rgba(122, 74, 45, 0.10); color: var(--blue);  border-color: transparent; }

/* ─────────────────────────── Animated SVG figures ─────────────────────────── */
.fig-anim { position: relative; }
.fig-anim svg { background: var(--paper); border-radius: 4px; }
.anim-controls {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  align-items: center;
  margin-top: 0.8rem;
}
.anim-controls button {
  font-family: var(--sans);
  font-size: 0.85rem;
  background: var(--paper);
  color: var(--ink);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 5px 12px;
  cursor: pointer;
  transition: background .15s, border-color .15s;
}
.anim-controls button:hover { background: var(--paper-dark); border-color: var(--rust); }
.anim-controls button.active { background: var(--rust); color: var(--paper); border-color: var(--rust); }
.anim-step {
  font-family: var(--mono);
  font-size: 0.78rem;
  color: var(--ink-faded);
  margin-left: auto;
}

/* Join Venn diagrams */
.venn-row { display: flex; gap: 0.8rem; flex-wrap: wrap; justify-content: center; margin: 1rem 0; }
.venn-card { flex: 1 1 160px; max-width: 200px; text-align: center; }
.venn-card svg { width: 100%; height: auto; }
.venn-card .vn-label { font-family: var(--mono); font-size: 0.78rem; color: var(--ink-faded); margin-top: 0.3rem; letter-spacing: 0.06em; }

/* Step-list */
.steps { counter-reset: stepcounter; list-style: none; padding-left: 0; }
.steps > li {
  counter-increment: stepcounter;
  position: relative;
  padding-left: 2.4rem;
  margin-bottom: 0.9rem;
}
.steps > li::before {
  content: counter(stepcounter);
  position: absolute;
  left: 0;
  top: 0.05em;
  width: 1.7rem;
  height: 1.7rem;
  background: var(--rust);
  color: var(--paper);
  font-family: var(--mono);
  font-size: 0.85rem;
  display: grid;
  place-items: center;
  border-radius: 50%;
}

/* Try-it editor */
.tryit {
  background: var(--paper-dark);
  border: 1px solid var(--line-soft);
  border-radius: 6px;
  padding: 1rem 1.2rem;
  margin: 1.4rem 0;
}
.tryit-label {
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--rust);
  margin-bottom: 0.5rem;
}
.tryit textarea {
  width: 100%;
  font-family: var(--mono);
  font-size: 0.9rem;
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 0.6rem 0.8rem;
  background: var(--paper);
  color: var(--ink);
  resize: vertical;
  min-height: 90px;
}
.tryit-btn {
  margin-top: 0.5rem;
  font-family: var(--sans);
  font-size: 0.85rem;
  background: var(--rust);
  color: var(--paper);
  border: none;
  padding: 6px 14px;
  border-radius: 14px;
  cursor: pointer;
}
.tryit-btn:hover { background: var(--rust-dark); }
.tryit-out {
  margin-top: 0.6rem;
  font-family: var(--mono);
  font-size: 0.85rem;
  background: var(--paper);
  border-left: 3px solid var(--green);
  padding: 0.6rem 0.9rem;
  white-space: pre-wrap;
  display: none;
}
.tryit-out.show { display: block; }
.tryit-out.err { border-left-color: #a83c32; color: #a83c32; }

/* Mini fact card grid */
.fact-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 0.8rem; margin: 1.4rem 0; }
.fact-card {
  background: var(--paper-dark);
  border: 1px solid var(--line-soft);
  border-radius: 6px;
  padding: 0.9rem 1rem;
}
.fact-card .fc-key {
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--rust);
  margin-bottom: 0.3rem;
}
.fact-card .fc-val { font-size: 0.95rem; color: var(--ink); line-height: 1.45; }

/* Decision tree / pseudo-table */
.decision {
  border: 1px solid var(--line-soft);
  border-radius: 6px;
  padding: 0.6rem 1rem;
  margin: 1.2rem 0;
  background: var(--paper-dark);
}
.decision summary {
  cursor: pointer;
  font-family: var(--sans);
  font-size: 0.95rem;
  color: var(--rust);
  padding: 0.4rem 0;
}
.decision[open] summary { color: var(--rust-dark); }
.decision-body { padding: 0.4rem 0 0.6rem; }

/* Pulse animation used by interactive figures */
@keyframes pulse-row {
  0%, 100% { fill: var(--paper); }
  50% { fill: rgba(31, 78, 121, 0.20); }
}
.row-pulse { animation: pulse-row 1.6s ease-in-out infinite; }

@keyframes fade-in {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}
.fade-in { animation: fade-in .35s ease-out both; }

/* Arrow animation for execution-order figure */
@keyframes arrow-trace {
  0% { stroke-dashoffset: 200; }
  100% { stroke-dashoffset: 0; }
}
.arrow-trace { stroke-dasharray: 200; animation: arrow-trace 1.4s ease-in-out forwards; }

/* ─────────────────────────── Sub-page list ─────────────────────────── */
.subpage-list { display: flex; flex-direction: column; gap: 0.8rem; margin: 1.5rem 0; }
.subpage-card {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1rem 1.2rem;
  background: var(--paper-dark);
  border: 1px solid var(--line-soft);
  border-radius: 6px;
  border-bottom: 1px solid var(--line-soft);
  color: var(--ink);
  transition: background .15s, border-color .15s, transform .15s;
}
.subpage-card:hover { background: var(--paper); border-color: var(--rust); transform: translateX(2px); }
.sp-icon {
  flex: 0 0 auto;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--rust);
  color: var(--paper);
  display: grid;
  place-items: center;
  font-family: var(--mono);
  font-weight: 700;
  font-size: 0.92rem;
}
.sp-info { flex: 1; min-width: 0; }
.sp-title { font-family: var(--serif); font-size: 1.1rem; color: var(--ink); }
.sp-desc { font-size: 0.9rem; color: var(--ink-faded); margin-top: 2px; }
.sp-arrow { font-family: var(--mono); color: var(--ink-ghost); font-size: 1.2rem; transition: color .15s, transform .15s; }
.subpage-card:hover .sp-arrow { color: var(--rust); transform: translateX(3px); }

/* ─────────────────────────── Tables / figures ─────────────────────────── */
.table-wrap { overflow-x: auto; margin: 1.4rem 0; }
table { width: 100%; border-collapse: collapse; font-family: var(--sans); font-size: 0.95rem; }
th, td { padding: 0.6rem 0.9rem; border-bottom: 1px solid var(--line-soft); text-align: left; vertical-align: top; }
th { font-family: var(--mono); font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--ink-faded); border-bottom: 1px solid var(--line); }
.mono-cell { font-family: var(--mono); font-size: 0.88rem; }

figure { margin: 1.6rem 0; padding: 1rem; background: var(--paper-dark); border-radius: 6px; }
figure svg { display: block; max-width: 100%; height: auto; margin: 0 auto; }
figcaption { font-family: var(--sans); font-size: 0.85rem; color: var(--ink-faded); text-align: center; margin-top: 0.6rem; font-style: italic; }

blockquote { border-left: 3px solid var(--line); padding-left: 1.2rem; margin: 1.2rem 0; color: var(--ink-soft); font-style: italic; }

/* ─────────────────────────── Footer ─────────────────────────── */
footer { padding: 4rem 0 3rem; border-top: 1px solid var(--line-soft); margin-top: 4rem; text-align: center; color: var(--ink-faded); }
.ornament { font-size: 1.4rem; color: var(--ink-ghost); margin-bottom: 1rem; letter-spacing: 0.6em; }
footer p { font-family: var(--mono); font-size: 0.78rem; letter-spacing: 0.1em; text-transform: uppercase; }

/* ─────────────────────────── Definition box ─────────────────────────── */
.def-box {
  background: rgba(31, 78, 121, 0.06);
  border: 1px solid rgba(31, 78, 121, 0.18);
  border-left: 4px solid var(--rust);
  padding: 1.1rem 1.4rem;
  margin: 1.6rem 0;
  border-radius: 4px;
}
.def-box .def-label { font-family: var(--mono); font-size: 0.72rem; letter-spacing: 0.16em; text-transform: uppercase; color: var(--rust); margin-bottom: 0.3rem; display: block; }
.def-box .def-term { font-family: var(--serif); font-size: 1.18rem; color: var(--ink); font-style: italic; margin-bottom: 0.4rem; }
.def-box p:last-child { margin-bottom: 0; }

/* ─────────────────────────── Compare grid (good/bad side-by-side) ─────────────────────────── */
.compare-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; margin: 1.4rem 0; }
.compare-grid .compare-cell { background: var(--paper-dark); border: 1px solid var(--line-soft); padding: 0.9rem 1.1rem; border-radius: 6px; }
.compare-grid .compare-cell h4 { margin: 0 0 0.5rem; color: var(--rust); }
.compare-grid .compare-cell.bad { border-left: 4px solid #b54e3a; }
.compare-grid .compare-cell.good { border-left: 4px solid var(--green); }
@media (max-width: 720px) { .compare-grid { grid-template-columns: 1fr; } }

/* ─────────────────────────── Example tables (color highlights) ─────────────────────────── */
.example-table { width: 100%; border-collapse: collapse; font-family: var(--mono); font-size: 0.86rem; margin: 0.8rem 0; }
.example-table th, .example-table td { padding: 0.35rem 0.6rem; border: 1px solid var(--line); text-align: left; }
.example-table th { background: var(--paper-dark); }
.example-table td.repeat { background: rgba(198, 138, 31, 0.18); }
.example-table td.anomaly { background: rgba(181, 78, 58, 0.16); }
.example-table tr.fresh td { background: rgba(61, 107, 58, 0.12); }
.example-table caption { font-family: var(--sans); font-size: 0.85rem; color: var(--ink-faded); text-align: left; margin-bottom: 0.3rem; font-style: italic; caption-side: top; }

/* ─────────────────────────── Normal-form ladder ─────────────────────────── */
.nf-ladder { display: flex; flex-direction: column; gap: 0.45rem; margin: 1.4rem 0; }
.nf-rung { display: grid; grid-template-columns: 80px 1fr; gap: 1rem; padding: 0.8rem 1rem; border: 1px solid var(--line-soft); background: var(--paper-dark); border-radius: 4px; align-items: start; }
.nf-rung .nf-name { font-family: var(--mono); font-weight: 700; color: var(--rust); font-size: 1rem; }
.nf-rung .nf-desc { font-size: 0.94rem; color: var(--ink-soft); }
.nf-rung.bcnf { border-color: var(--rust); background: rgba(31,78,121,0.08); }
@media (max-width: 720px) { .nf-rung { grid-template-columns: 60px 1fr; } }

/* ─────────────────────────── Functional-dependency / closure tool ─────────────────────────── */
.fd-tool { background: var(--paper-dark); border: 1px solid var(--line-soft); padding: 1.1rem; border-radius: 6px; margin: 1.4rem 0; }
.fd-tool .fd-set { font-family: var(--mono); font-size: 0.92rem; margin-bottom: 0.7rem; color: var(--ink-soft); }
.fd-tool .fd-pick { display: flex; flex-wrap: wrap; gap: 6px; margin: 0.3rem 0 0.8rem; }
.fd-tool .pick-btn { font-family: var(--mono); font-size: 0.95rem; padding: 5px 12px; border-radius: 16px; background: var(--paper); color: var(--ink); border: 1px solid var(--line); cursor: pointer; }
.fd-tool .pick-btn.active { background: var(--rust); color: var(--paper); border-color: var(--rust); }
.fd-tool .fd-go { font-family: var(--sans); padding: 6px 14px; border-radius: 16px; background: var(--rust); color: var(--paper); border: none; cursor: pointer; font-size: 0.88rem; }
.fd-tool .fd-go:hover { background: var(--rust-dark); }
.fd-tool .fd-out { margin-top: 0.9rem; font-family: var(--mono); font-size: 0.9rem; }
.fd-tool .fd-out .step { padding: 0.25rem 0; border-bottom: 1px dashed var(--line-soft); }
.fd-tool .fd-out .step:last-child { border-bottom: none; }
.fd-tool .closure-result { margin-top: 0.6rem; padding: 0.5rem 0.7rem; background: var(--paper); border-left: 3px solid var(--green); font-family: var(--mono); }
.fd-tool .verdict { margin-top: 0.4rem; font-family: var(--sans); }

/* ─────────────────────────── Recap pill grid ─────────────────────────── */
.recap-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 0.6rem; margin: 1.2rem 0; }
.recap-grid .recap-pill { background: var(--paper); border: 1px solid var(--line-soft); border-radius: 4px; padding: 0.6rem 0.8rem; font-size: 0.9rem; line-height: 1.4; }
.recap-grid .recap-pill strong { color: var(--rust); display: block; font-family: var(--mono); font-size: 0.74rem; letter-spacing: 0.1em; text-transform: uppercase; margin-bottom: 0.2rem; }

/* ─────────────────────────── Warn / good callouts ─────────────────────────── */
.callout-warn { background: rgba(181, 78, 58, 0.06); border-left-color: #b54e3a; }
.callout-warn .label { color: #b54e3a; }
.callout-good { background: rgba(61, 107, 58, 0.06); border-left-color: var(--green); }
.callout-good .label { color: var(--green); }

/* ─────────────────────────── ER diagram SVG palette ─────────────────────────── */
.svg-fig text { font-family: var(--sans); fill: var(--ink); font-size: 13px; }
.svg-fig .label-mono { font-family: var(--mono); font-size: 12px; fill: var(--ink-soft); }
.svg-fig .ent-rect { fill: var(--paper); stroke: var(--ink); stroke-width: 1.5; }
.svg-fig .ent-weak-outer { fill: none; stroke: var(--ink); stroke-width: 1.4; }
.svg-fig .attr-oval { fill: var(--paper); stroke: var(--ink-faded); stroke-width: 1.2; }
.svg-fig .attr-oval.key { stroke: var(--rust); }
.svg-fig .attr-oval.multi { stroke-dasharray: 4 3; }
.svg-fig .rel-diamond { fill: var(--paper); stroke: var(--ink); stroke-width: 1.5; }
.svg-fig .edge { fill: none; stroke: var(--ink); stroke-width: 1.3; }
.svg-fig .edge.double { stroke-width: 3.6; }
.svg-fig .key-text { text-decoration: underline; }

/* legend strip */
.legend { display: flex; flex-wrap: wrap; gap: 0.9rem; font-family: var(--mono); font-size: 0.78rem; color: var(--ink-soft); margin-top: 0.6rem; justify-content: center; }
.legend .swatch { display: inline-block; width: 14px; height: 14px; vertical-align: middle; margin-right: 4px; border: 1px solid var(--line); }

/* ─────────────────────────── Lang switch (unused but present) ─────────────────────────── */
.lang-switch { display: none; }

/* ─────────────────────────── Responsive ─────────────────────────── */
@media (max-width: 720px) {
  html, body { font-size: 17px; }
  h1 { font-size: 2.4rem; }
  h2 { font-size: 1.6rem; }
  .container { padding: 0 22px; }
  .hero { padding: 2.5rem 0 1.5rem; }
  section { padding: 2rem 0; }
  .nav-search-wrapper { display: none; }
  .site-nav .container { gap: 14px; }
  .chapter-toc-list { flex-direction: column; gap: 0.6rem; }
}