/* ============================================================
   CE Encyclopedia — Design System
   Based on compound-engineering brand: #C9EFFA (light) / #6366f1 (indigo)
   ============================================================ */

:root {
  /* Brand */
  --brand-light: #C9EFFA;
  --brand-primary: #6366f1;
  --brand-primary-dark: #4f46e5;
  --brand-accent: #06b6d4;
  --brand-warm: #f59e0b;

  /* Surfaces */
  --bg: #ffffff;
  --bg-soft: #f8fafc;
  --bg-code: #1e293b;
  --bg-code-soft: #0f172a;
  --bg-card: #ffffff;
  --bg-stripe: #f1f5f9;
  --bg-callout: #fffbeb;

  /* Borders */
  --border: #e2e8f0;
  --border-strong: #cbd5e1;
  --border-focus: var(--brand-primary);

  /* Text */
  --text: #1e293b;
  --text-soft: #475569;
  --text-muted: #64748b;
  --text-faint: #94a3b8;
  --text-inverse: #f1f5f9;
  --text-code: #e2e8f0;

  /* Status */
  --ok: #059669;
  --warn: #d97706;
  --err: #dc2626;
  --info: #2563eb;
  --neutral: #64748b;

  /* Typography */
  --font-serif: "Source Serif Pro", "Charter", "Iowan Old Style", "Apple Garamond", Georgia, "Times New Roman", serif;
  --font-sans: -apple-system, BlinkMacSystemFont, "Inter", "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", "Source Code Pro", "SF Mono", "Menlo", "Consolas", monospace;

  /* Sizing */
  --max-w: 78ch;
  --max-w-wide: 92ch;
  --radius: 8px;
  --radius-sm: 4px;
  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.06);
  --shadow: 0 4px 16px rgba(15, 23, 42, 0.08);
  --shadow-lg: 0 12px 40px rgba(15, 23, 42, 0.12);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

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

/* ----- Layout ----- */

.layout {
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  background: var(--bg-soft);
  border-right: 1px solid var(--border);
  padding: 28px 22px;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
}

.sidebar-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 14px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--brand-primary);
  margin-bottom: 24px;
}

.sidebar-brand-dot {
  width: 10px;
  height: 10px;
  background: var(--brand-primary);
  border-radius: 50%;
  box-shadow: 0 0 0 4px var(--brand-light);
}

.sidebar h4 {
  font-family: var(--font-sans);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin: 24px 0 8px;
}

.sidebar ul { list-style: none; padding: 0; margin: 0; }
.sidebar li { margin: 0; }

.sidebar a {
  display: block;
  padding: 12px 10px;
  font-family: var(--font-sans);
  font-size: 14px;
  color: var(--text-soft);
  text-decoration: none;
  border-radius: var(--radius-sm);
  border-left: 2px solid transparent;
  transition: background 0.1s, color 0.1s;
}

.sidebar a:hover {
  background: var(--bg-stripe);
  color: var(--text);
}

.sidebar a:focus-visible {
  outline: 2px solid var(--brand-primary);
  outline-offset: -2px;
  background: var(--bg-stripe);
  color: var(--text);
}

.sidebar a.active {
  background: var(--bg-card);
  border-left-color: var(--brand-primary);
  color: var(--brand-primary-dark);
  font-weight: 600;
}

.main { padding: 40px 60px 80px; max-width: 1100px; }

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 24px;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 10;
  font-family: var(--font-sans);
}

.topbar-brand {
  font-weight: 700;
  font-size: 14px;
  color: var(--brand-primary);
}

.topbar-search input {
  font-family: var(--font-sans);
  font-size: 14px;
  padding: 8px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  width: 280px;
  background: var(--bg-soft);
}

.topbar-search input:focus {
  outline: none;
  border-color: var(--brand-primary);
  background: var(--bg);
}

/* ----- Typography ----- */

h1, h2, h3, h4, h5 {
  font-family: var(--font-sans);
  color: var(--text);
  letter-spacing: -0.01em;
  margin: 1.6em 0 0.5em;
  line-height: 1.25;
}

h1 {
  font-size: 48px;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-top: 0;
  line-height: 1.15;
}

h2 {
  font-size: 30px;
  font-weight: 700;
  border-bottom: 1px solid var(--border);
  padding-bottom: 6px;
  margin-top: 2.2em;
}

h3 {
  font-size: 23px;
  font-weight: 600;
  margin-top: 1.6em;
}

h4 {
  font-size: 14px;
  font-weight: 600;
  margin-top: 1.4em;
  color: var(--text-soft);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

p { margin: 0.9em 0; }

a { color: var(--brand-primary); text-decoration: none; border-bottom: 1px solid transparent; }
a:hover { border-bottom-color: var(--brand-primary); }

strong { color: var(--text); font-weight: 600; }

ul, ol { padding-left: 1.4em; }
li { margin: 0.3em 0; }

code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--bg-stripe);
  color: #b91c1c;
  padding: 1px 5px;
  border-radius: 3px;
  border: 1px solid var(--border);
}

pre {
  background: var(--bg-code);
  color: var(--text-code);
  padding: 16px 18px;
  border-radius: var(--radius);
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 14px;
  line-height: 1.55;
  border: 1px solid var(--border-strong);
  box-shadow: var(--shadow-sm);
}

pre code {
  background: transparent;
  color: inherit;
  padding: 0;
  border: 0;
  font-size: inherit;
}

/* Inline highlighting classes inside pre */
.tk-key { color: #93c5fd; }
.tk-str { color: #86efac; }
.tk-com { color: #94a3b8; font-style: italic; }
.tk-num { color: #fbbf24; }
.tk-fn  { color: #f9a8d4; }
.tk-var { color: #fde68a; }
.tk-fl  { color: #f87171; font-weight: 600; }
.tk-path { color: #c4b5fd; }

blockquote {
  margin: 1.2em 0;
  padding: 14px 22px;
  background: var(--bg-soft);
  color: var(--text-soft);
  font-style: italic;
  border-radius: var(--radius);
}

hr {
  border: 0;
  height: 1px;
  background: var(--border);
  margin: 2.5em 0;
}

/* ----- Tables ----- */

table {
  border-collapse: collapse;
  width: 100%;
  margin: 1.4em 0;
  font-family: var(--font-sans);
  font-size: 14px;
  background: var(--bg-card);
  box-shadow: var(--shadow-sm);
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--border);
}

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

th {
  background: var(--bg-stripe);
  font-weight: 600;
  color: var(--text-soft);
  font-size: 14px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

tr:last-child td { border-bottom: 0; }
tr:hover td { background: var(--bg-soft); }

td code { font-size: 14px; }

/* ----- Callouts ----- */

.callout {
  margin: 1.5em 0;
  padding: 16px 20px;
  border-radius: var(--radius);
  font-family: var(--font-sans);
  font-size: 14px;
}

.callout p:first-child { margin-top: 0; }
.callout p:last-child  { margin-bottom: 0; }

.callout-note   { background: #eff6ff; color: #1e3a8a; }
.callout-warn   { background: #fffbeb; color: #78350f; }
.callout-tip    { background: #ecfdf5; color: #064e3b; }
.callout-danger { background: #fef2f2; color: #7f1d1d; }
.callout-rule   { background: #f5f3ff; color: #3730a3; }

.callout-title {
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  font-size: 14px;
  margin-bottom: 6px;
}

/* ----- Skill Card ----- */

.skill-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 14px;
  margin: 1.4em 0;
}

.skill-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 18px;
  transition: transform 0.1s, box-shadow 0.1s, border-color 0.1s;
}

.skill-card:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow);
  border-color: var(--brand-primary);
}

.skill-card .name {
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 14px;
  color: var(--brand-primary-dark);
  margin-bottom: 4px;
}

.skill-card .badge {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 1px 7px;
  border-radius: 99px;
  background: var(--brand-light);
  color: #0c4a6e;
  margin-bottom: 6px;
}

.skill-card .badge.disabled { background: #fef3c7; color: #92400e; }
.skill-card .badge.internal { background: #ede9fe; color: #5b21b6; }

.skill-card .desc {
  font-size: 14px;
  color: var(--text-soft);
  line-height: 1.5;
}

/* ----- Status badges ----- */

.status {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 14px;
  font-weight: 600;
  padding: 2px 8px;
  border-radius: 4px;
  white-space: nowrap;
}

.status.ok    { background: #d1fae5; color: #065f46; }
.status.warn  { background: #fef3c7; color: #92400e; }
.status.err   { background: #fee2e2; color: #991b1b; }
.status.info  { background: #dbeafe; color: #1e40af; }
.status.neutral { background: var(--bg-stripe); color: var(--text-muted); }
.status.mode  { background: #ede9fe; color: #5b21b6; }

/* ----- Diagrams ----- */

.diagram {
  margin: 1.6em 0;
  padding: 16px;
  background: var(--bg-soft);
  border-radius: var(--radius);
  border: 1px solid var(--border);
}

.diagram-caption {
  font-family: var(--font-sans);
  font-size: 14px;
  color: var(--text-muted);
  text-align: center;
  margin-top: 8px;
}

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

/* ----- Code with caption ----- */

.figure {
  margin: 1.6em 0;
}

.figure-title {
  font-family: var(--font-sans);
  font-size: 14px;
  font-weight: 600;
  color: var(--text-soft);
  margin-bottom: 6px;
  letter-spacing: 0.02em;
}

/* ----- Definition list ----- */

dl { margin: 1em 0; }
dt {
  font-family: var(--font-sans);
  font-weight: 600;
  color: var(--text-soft);
  margin-top: 0.8em;
  font-size: 14px;
}
dd {
  margin-left: 1.2em;
  color: var(--text);
}

/* ----- Page navigation ----- */

.page-nav {
  display: flex;
  justify-content: space-between;
  align-items: stretch;
  gap: 16px;
  margin: 3em 0 1em;
  padding: 18px 0;
  border-top: 1px solid var(--border);
  font-family: var(--font-sans);
  font-size: 14px;
}

.toc-card a:focus-visible,
.page-nav a:focus-visible {
  outline: 2px solid var(--brand-primary);
  outline-offset: 2px;
}

.page-nav a {
  flex: 1;
  padding: 14px 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  background: var(--bg-card);
  transition: border-color 0.1s, background 0.1s;
}

.page-nav a:hover {
  border-color: var(--brand-primary);
  background: var(--bg-soft);
}

.page-nav .prev { text-align: left; }
.page-nav .next { text-align: right; margin-left: auto; }

.page-nav .label {
  font-size: 14px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 2px;
}

.page-nav .title {
  font-weight: 600;
  color: var(--text);
}

/* ----- TOC on landing page ----- */

.toc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 18px;
  margin: 1.6em 0;
}

.toc-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 18px;
  transition: border-color 0.1s, transform 0.1s;
}

.toc-card:hover {
  border-color: var(--brand-primary);
  transform: translateY(-1px);
}

.toc-card h3 {
  font-family: var(--font-sans);
  font-size: 14px;
  font-weight: 700;
  color: var(--brand-primary-dark);
  margin: 0 0 4px;
}

.toc-card p {
  font-family: var(--font-sans);
  font-size: 14px;
  color: var(--text-soft);
  margin: 0;
  line-height: 1.4;
}

.toc-card ul {
  font-family: var(--font-sans);
  font-size: 14px;
  margin: 8px 0 0;
  padding-left: 18px;
}

.toc-card li { margin: 2px 0; }
.toc-card a { color: var(--text-soft); }
.toc-card a:hover { color: var(--brand-primary); }

/* ----- Hero ----- */

.hero {
  text-align: left;
  padding: 28px 0 16px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 12px;
}

.hero .eyebrow {
  font-family: var(--font-sans);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--brand-primary);
  margin-bottom: 8px;
}

.hero h1 {
  font-size: 60px;
  letter-spacing: -0.025em;
}

.hero p.lead {
  font-size: 18px;
  color: var(--text-soft);
  max-width: 60ch;
  line-height: 1.55;
}

/* ----- Tag list ----- */

.tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 14px;
  padding: 2px 8px;
  border-radius: 99px;
  background: var(--bg-stripe);
  color: var(--text-soft);
  margin: 2px;
}

/* ----- Responsive ----- */

@media (max-width: 900px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar { position: relative; height: auto; border-right: 0; border-bottom: 1px solid var(--border); }
  .main { padding: 24px 24px 60px; }
  .hero h1 { font-size: 38px; }
}

/* Skip-link (keyboard accessibility) */
.skip-link {
  position: absolute;
  top: -100px;
  left: 0;
  padding: 12px 18px;
  background: var(--brand-primary);
  color: #ffffff;
  font-family: var(--font-sans);
  font-size: 14px;
  font-weight: 600;
  text-decoration: none;
  border-radius: 0 0 var(--radius-sm) 0;
  z-index: 100;
}
.skip-link:focus {
  top: 0;
  outline: 2px solid var(--brand-primary-dark);
  outline-offset: -2px;
}

/* prefers-reduced-motion (WCAG 2.3.3) */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

@media print {
  .sidebar, .topbar, .page-nav { display: none; }
  .main { max-width: 100%; padding: 0; }
  body { font-size: 12pt; }
}

/* ----- Search highlight ----- */

mark {
  background: #fef08a;
  color: var(--text);
  padding: 0 3px;
  border-radius: 2px;
}

/* ----- Reading guide badges ----- */

.level {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.06em;
  padding: 2px 9px;
  border-radius: 4px;
  margin-right: 6px;
  text-transform: uppercase;
}

.level.intro    { background: #dbeafe; color: #1e3a8a; }
.level.intermediate { background: #fef3c7; color: #78350f; }
.level.advanced { background: #fee2e2; color: #7f1d1d; }
.level.reference { background: #f3e8ff; color: #5b21b6; }