/*
  DCAI 300-640 Study Guide — original stylesheet.
  No frameworks, no build step. Mobile-first, then enhanced for wider screens.
*/

:root {
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;

  --bg: #f5f7fb;
  --bg-elevated: #ffffff;
  --bg-sunken: #eaeef5;
  --text: #182233;
  --text-muted: #4c5769;
  --text-faint: #6b7686;
  --border: #d7dee8;
  --border-strong: #b7c2d3;
  --accent: #0b5fae;
  --accent-strong: #08427a;
  --accent-contrast: #ffffff;
  --accent-soft: #e3edfa;
  --domain1: #0b6e4f;
  --domain2: #0b5fae;
  --domain3: #7a4b9c;
  --domain4: #ad5a08;
  --focus-ring: #c8590d;
  --code-bg: #10233d;
  --code-text: #dce8fb;
  --shadow: 0 1px 2px rgba(20, 30, 50, 0.06), 0 8px 24px -12px rgba(20, 30, 50, 0.18);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --header-h: 56px;
  --transition-fast: 140ms ease;
}

[data-theme="dark"] {
  --bg: #10151f;
  --bg-elevated: #171f2c;
  --bg-sunken: #0b0f17;
  --text: #e7ecf5;
  --text-muted: #b7c1d3;
  --text-faint: #8b96a9;
  --border: #2a3446;
  --border-strong: #3a465c;
  --accent: #63a6f2;
  --accent-strong: #9cc6ff;
  --accent-contrast: #05131f;
  --accent-soft: #17263c;
  --domain1: #4fbf8f;
  --domain2: #63a6f2;
  --domain3: #b98ee8;
  --domain4: #f0a94e;
  --focus-ring: #ffb454;
  --code-bg: #0a1524;
  --code-text: #cfe3ff;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 12px 28px -14px rgba(0, 0, 0, 0.6);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scrollbar-gutter: stable; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { animation-duration: 0.001ms !important; animation-iteration-count: 1 !important; transition-duration: 0.001ms !important; scroll-behavior: auto !important; }
}

body {
  margin: 0;
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
  overflow-x: hidden;
}

a { color: var(--accent); }
a:hover { color: var(--accent-strong); }
code, kbd { font-family: var(--font-mono); font-size: 0.92em; }
code { background: var(--bg-sunken); padding: 0.1em 0.4em; border-radius: 4px; }
kbd { background: var(--code-bg); color: var(--code-text); padding: 0.05em 0.45em; border-radius: 4px; border-bottom: 2px solid rgba(0,0,0,0.35); }

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

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--accent);
  color: var(--accent-contrast);
  padding: 0.75rem 1.25rem;
  z-index: 1000;
  border-radius: 0 0 8px 0;
  font-weight: 600;
}
.skip-link:focus { left: 0; }

/* ---------- progress bar ---------- */
#progress-bar {
  position: fixed;
  top: 0; left: 0;
  height: 3px;
  width: 0%;
  background: linear-gradient(90deg, var(--domain1), var(--domain2), var(--domain3), var(--domain4));
  z-index: 60;
  transition: width 80ms linear;
}

/* ---------- header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-h);
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0 0.75rem;
  background: color-mix(in srgb, var(--bg-elevated) 92%, transparent);
  backdrop-filter: saturate(1.4) blur(8px);
  border-bottom: 1px solid var(--border);
}

.nav-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px; height: 40px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text);
  cursor: pointer;
}
.nav-toggle:hover { background: var(--bg-sunken); }

.brand {
  display: flex;
  flex-direction: column;
  line-height: 1.15;
  margin-right: auto;
  min-width: 0;
}
.brand-title { font-weight: 800; font-size: 0.98rem; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.brand-sub { font-size: 0.72rem; color: var(--text-faint); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }

.header-actions { display: flex; align-items: center; gap: 0.4rem; }
.icon-btn {
  width: 40px; height: 40px;
  display: inline-flex; align-items: center; justify-content: center;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text);
  cursor: pointer;
  font-size: 1rem;
}
.icon-btn:hover { background: var(--bg-sunken); }

/* ---------- layout shell ---------- */
.layout {
  display: flex;
  min-height: calc(100vh - var(--header-h));
}

.sidebar {
  position: fixed;
  top: var(--header-h);
  left: 0;
  bottom: 0;
  width: 290px;
  overflow-y: auto;
  background: var(--bg-elevated);
  border-right: 1px solid var(--border);
  padding: 0.85rem 0.75rem 3rem;
  transform: translateX(-100%);
  transition: transform var(--transition-fast);
  z-index: 45;
}
.sidebar.is-open { transform: translateX(0); }

.sidebar-scrim {
  position: fixed;
  inset: var(--header-h) 0 0 0;
  background: rgba(10, 14, 22, 0.45);
  z-index: 40;
  display: none;
}
.sidebar-scrim.is-open { display: block; }

@media (min-width: 960px) {
  .nav-toggle { display: none; }
  .sidebar { position: sticky; transform: none; top: var(--header-h); height: calc(100vh - var(--header-h)); }
  .sidebar-scrim { display: none !important; }
}

.search-field {
  position: relative;
  margin-bottom: 0.75rem;
}
.search-field input {
  width: 100%;
  padding: 0.55rem 2.2rem 0.55rem 0.7rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-strong);
  background: var(--bg-sunken);
  color: var(--text);
  font-size: 0.9rem;
}
.search-field .clear-btn {
  position: absolute;
  right: 0.35rem;
  top: 50%;
  transform: translateY(-50%);
  border: none;
  background: transparent;
  color: var(--text-faint);
  cursor: pointer;
  font-size: 1rem;
  padding: 0.2rem 0.4rem;
}
.search-hint { font-size: 0.72rem; color: var(--text-faint); margin: -0.4rem 0 0.75rem; }

.expand-controls { display: flex; gap: 0.4rem; margin-bottom: 0.9rem; }
.expand-controls button {
  flex: 1;
  font-size: 0.78rem;
  padding: 0.4rem 0.3rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-strong);
  background: var(--bg-sunken);
  color: var(--text);
  cursor: pointer;
}
.expand-controls button:hover { background: var(--accent-soft); }

.nav-domain { margin-bottom: 0.9rem; }
.nav-domain-title {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.5rem;
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--text-faint);
  padding: 0.3rem 0.4rem;
}
.nav-domain-title .weight-chip { font-weight: 700; }
.nav-list { list-style: none; margin: 0; padding: 0; }
.nav-list a {
  display: flex;
  gap: 0.5rem;
  align-items: baseline;
  text-decoration: none;
  color: var(--text);
  font-size: 0.86rem;
  padding: 0.42rem 0.5rem;
  border-radius: var(--radius-sm);
}
.nav-list a:hover { background: var(--accent-soft); }
.nav-list a.is-active { background: var(--accent-soft); color: var(--accent-strong); font-weight: 700; }
.nav-list .obj-num { color: var(--text-faint); font-variant-numeric: tabular-nums; min-width: 2.1em; }

.sidebar-foot {
  margin-top: 1.2rem;
  padding-top: 0.8rem;
  border-top: 1px solid var(--border);
  font-size: 0.76rem;
  color: var(--text-faint);
}
.sidebar-foot a { display: block; margin-bottom: 0.3rem; }

/* ---------- main content ---------- */
main {
  flex: 1;
  min-width: 0;
  padding: 1.1rem 1rem 4rem;
  max-width: 980px;
  margin: 0 auto;
  width: 100%;
}

.disclaimer-banner {
  background: var(--accent-soft);
  border: 1px solid var(--border-strong);
  border-left: 5px solid var(--accent);
  border-radius: var(--radius-md);
  padding: 0.75rem 1rem;
  font-size: 0.86rem;
  margin-bottom: 1.1rem;
}
.disclaimer-banner strong { color: var(--accent-strong); }

.hero {
  padding: 1.4rem 0 1rem;
}
.hero h1 { margin: 0 0 0.35rem; font-size: clamp(1.5rem, 4vw, 2.1rem); letter-spacing: -0.01em; }
.hero p.lede { color: var(--text-muted); max-width: 62ch; margin: 0 0 0.9rem; }
.hero-meta { display: flex; flex-wrap: wrap; gap: 0.5rem 1rem; font-size: 0.82rem; color: var(--text-faint); }
.hero-meta a { color: var(--accent); }

.weight-overview {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 0.7rem;
  margin: 1.1rem 0 1.6rem;
}
.weight-card {
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 0.75rem 0.85rem;
  background: var(--bg-elevated);
  box-shadow: var(--shadow);
}
.weight-card .wc-top { display: flex; justify-content: space-between; font-size: 0.78rem; font-weight: 700; color: var(--text-muted); margin-bottom: 0.4rem;}
.weight-card .wc-pct { font-size: 1.5rem; font-weight: 800; }
.weight-bar { height: 8px; border-radius: 6px; background: var(--bg-sunken); overflow: hidden; margin-top: 0.5rem;}
.weight-bar > span { display: block; height: 100%; border-radius: 6px; }
.d1 .wc-pct, .d1 .weight-bar>span { color: var(--domain1); background: var(--domain1); }
.d2 .wc-pct, .d2 .weight-bar>span { color: var(--domain2); background: var(--domain2); }
.d3 .wc-pct, .d3 .weight-bar>span { color: var(--domain3); background: var(--domain3); }
.d4 .wc-pct, .d4 .weight-bar>span { color: var(--domain4); background: var(--domain4); }

.section-heading { display:flex; align-items:center; gap:0.5rem; margin: 2.1rem 0 0.6rem; scroll-margin-top: calc(var(--header-h) + 12px); }
.section-heading h2 { margin: 0; font-size: 1.35rem; }
.section-heading .anchor-link { font-size: 0.85rem; color: var(--text-faint); text-decoration: none; }
.section-heading .anchor-link:hover { color: var(--accent); }

details.matrix-details summary { cursor: pointer; font-weight: 700; padding: 0.5rem 0; }

.matrix-wrap { overflow-x: auto; border: 1px solid var(--border); border-radius: var(--radius-md); }
table.coverage-matrix { width: 100%; border-collapse: collapse; font-size: 0.85rem; min-width: 560px; }
table.coverage-matrix caption { text-align: left; padding: 0.6rem 0.8rem; color: var(--text-faint); font-size: 0.8rem; }
table.coverage-matrix th, table.coverage-matrix td { text-align: left; padding: 0.5rem 0.75rem; border-bottom: 1px solid var(--border); vertical-align: top; }
table.coverage-matrix thead th { background: var(--bg-sunken); position: sticky; top: 0; }
table.coverage-matrix tbody tr:hover { background: var(--accent-soft); }

/* ---------- domain section ---------- */
.domain-section { margin-top: 2.4rem; scroll-margin-top: calc(var(--header-h) + 12px); }
.domain-banner {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.9rem 1rem;
  border-radius: var(--radius-lg);
  color: #fff;
  margin-bottom: 1rem;
}
.domain-banner h2 { margin: 0; font-size: 1.25rem; }
.domain-banner .domain-num { font-size: 0.78rem; opacity: 0.85; display:block; font-weight: 600; }
.domain-banner .domain-weight { margin-left: auto; font-weight: 800; font-size: 1.15rem; white-space: nowrap; }
.domain-1 .domain-banner, .domain-1 .domain-banner { background: linear-gradient(135deg, var(--domain1), #0a5540); }
.domain-2 .domain-banner { background: linear-gradient(135deg, var(--domain2), #073f73); }
.domain-3 .domain-banner { background: linear-gradient(135deg, var(--domain3), #522f6b); }
.domain-4 .domain-banner { background: linear-gradient(135deg, var(--domain4), #7a3d05); }

/* ---------- objective card ---------- */
.objective-card {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--bg-elevated);
  margin-bottom: 1rem;
  box-shadow: var(--shadow);
  scroll-margin-top: calc(var(--header-h) + 12px);
}
.obj-toggle {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 0.7rem;
  padding: 0.9rem 1rem;
  background: transparent;
  border: none;
  cursor: pointer;
  text-align: left;
  color: var(--text);
  font: inherit;
}
.obj-toggle .obj-badge {
  flex: none;
  width: 2.6rem;
  height: 2.6rem;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 0.85rem;
  color: #fff;
}
.domain-1 .obj-badge { background: var(--domain1); }
.domain-2 .obj-badge { background: var(--domain2); }
.domain-3 .obj-badge { background: var(--domain3); }
.domain-4 .obj-badge { background: var(--domain4); }
.obj-toggle .obj-title { font-weight: 700; font-size: 1.02rem; flex: 1; min-width: 0; }
.obj-toggle .obj-blueprint { display:block; font-weight: 500; font-size: 0.78rem; color: var(--text-faint); margin-top: 0.15rem; }
.obj-toggle .chev { flex: none; transition: transform var(--transition-fast); color: var(--text-faint); }
.obj-toggle[aria-expanded="true"] .chev { transform: rotate(90deg); }

.obj-body {
  padding: 0 1.15rem 1.25rem;
  border-top: 1px solid var(--border);
}
.obj-body[hidden] { display: none; }

.obj-block { margin-top: 1.1rem; }
.obj-block h3 {
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-faint);
  margin: 0 0 0.4rem;
}
.obj-block p, .obj-block li { font-size: 0.94rem; }
.obj-block ul, .obj-block ol { margin: 0.3rem 0; padding-left: 1.3rem; }
.obj-block ul li, .obj-block ol li { margin-bottom: 0.3rem; }

.takeaways { background: var(--accent-soft); border-radius: var(--radius-md); padding: 0.8rem 1rem; }
.misconception { background: color-mix(in srgb, var(--focus-ring) 12%, var(--bg-elevated)); border: 1px dashed var(--border-strong); border-radius: var(--radius-md); padding: 0.8rem 1rem; }
.scenario { border-left: 4px solid var(--accent); padding: 0.2rem 0 0.2rem 0.85rem; }

figure.diagram-figure {
  margin: 0.4rem 0 0;
  padding: 0.85rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--bg-sunken);
  overflow-x: auto;
}
figure.diagram-figure figcaption { font-size: 0.8rem; color: var(--text-faint); margin-top: 0.5rem; }
.diagram-svg { width: 100%; height: auto; display: block; min-width: 460px; }
.dg-node, .dg-layer { fill: var(--bg-elevated); stroke: var(--border-strong); stroke-width: 1.5; }
.dg-hub { fill: var(--accent-soft); stroke: var(--accent); stroke-width: 1.75; }
.dg-label { fill: var(--text); font-size: 12px; font-family: var(--font-sans); font-weight: 600; }
.dg-sublabel { fill: var(--text-faint); font-size: 10.5px; font-family: var(--font-sans); }
.dg-edge { stroke: var(--border-strong); stroke-width: 2; }
.dg-edge-return { stroke: var(--accent); stroke-dasharray: 4 3; }
.dg-arrowhead { fill: var(--border-strong); }

.source-list { font-size: 0.82rem; color: var(--text-faint); }
.source-list a { color: var(--text-muted); }
.source-list a:hover { color: var(--accent); }

.tag-chip { display:inline-block; font-size: 0.68rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.03em; padding: 0.1rem 0.4rem; border-radius: 5px; margin-left: 0.4rem; }
.tag-illustrative { background: color-mix(in srgb, var(--focus-ring) 18%, transparent); color: var(--focus-ring); }
.tag-versioned { background: color-mix(in srgb, var(--accent) 18%, transparent); color: var(--accent); }

/* filtering */
.objective-card.is-hidden { display: none; }
.no-results { padding: 1.5rem; text-align: center; color: var(--text-faint); border: 1px dashed var(--border-strong); border-radius: var(--radius-md); }

/* ---------- bibliography / footer ---------- */
.bibliography { columns: 1; column-gap: 2rem; font-size: 0.85rem; }
@media (min-width: 720px) { .bibliography { columns: 2; } }
.bibliography li { break-inside: avoid; margin-bottom: 0.5rem; }

.site-footer {
  margin-top: 2.5rem;
  padding-top: 1.4rem;
  border-top: 1px solid var(--border);
  font-size: 0.82rem;
  color: var(--text-faint);
}
.site-footer a { color: var(--text-muted); }
.footer-links { display: flex; flex-wrap: wrap; gap: 0.4rem 1.1rem; margin-bottom: 0.8rem; }

.back-to-top {
  position: fixed;
  right: 1.1rem;
  bottom: 1.1rem;
  width: 44px; height: 44px;
  border-radius: 50%;
  border: 1px solid var(--border-strong);
  background: var(--accent);
  color: #fff;
  font-size: 1.1rem;
  cursor: pointer;
  box-shadow: var(--shadow);
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-fast);
  z-index: 55;
}
.back-to-top.is-visible { opacity: 1; pointer-events: auto; }

.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
  white-space: nowrap;
  border: 0;
}

/* ---------- print ---------- */
@media print {
  .site-header, .sidebar, .sidebar-scrim, .back-to-top, .expand-controls, .search-field, .nav-toggle, #progress-bar { display: none !important; }
  main { max-width: none; padding: 0; }
  .obj-body[hidden] { display: block !important; }
  .objective-card { break-inside: avoid; box-shadow: none; border-color: #999; }
  a { color: inherit; text-decoration: underline; }
  body { background: #fff; color: #000; }
  .diagram-svg { min-width: 0; }
}