/* =========================================================================
   compactionstrategy.org — light, professional teal/emerald theme
   ========================================================================= */

:root {
  /* Palette */
  --teal-50:  #f0fdfa;
  --teal-100: #ccfbf1;
  --teal-200: #a7f3eb;
  --teal-500: #14b8a6;
  --teal-600: #0d9488;
  --teal-700: #0f766e;
  --teal-800: #155e63;
  --amber-400:#fbbf24;
  --amber-500:#f59e0b;
  --indigo-500:#6366f1;
  --rose-500: #f43f5e;
  --sky-500:  #0ea5e9;

  /* Semantic */
  --bg:        #f7faf9;
  --bg-soft:   #eef5f3;
  --surface:   #ffffff;
  --surface-2: #f3f8f7;
  --border:    #d9e6e3;
  --border-strong: #c4d8d4;
  --text:      #1c2b29;
  --text-soft: #4b605c;
  --text-muted:#6b807c;
  --primary:   var(--teal-700);
  --primary-hover: var(--teal-800);
  --accent:    var(--amber-500);
  --link:      var(--teal-700);
  --link-hover:var(--teal-800);

  /* Code */
  --code-bg:    #f4f8f7;
  --code-inline-bg: #eef4f2;
  --code-border:#e0ebe8;
  --code-text:  #1f3b38;

  /* Metrics */
  --header-h: 4rem;
  --maxw: 88rem;          /* widescreen container */
  --measure: 78rem;       /* article content width on desktop */
  --radius: 14px;
  --radius-sm: 9px;
  --shadow-sm: 0 1px 2px rgba(15, 118, 110, 0.06), 0 1px 3px rgba(15, 118, 110, 0.08);
  --shadow-md: 0 6px 18px rgba(15, 94, 99, 0.10), 0 2px 6px rgba(15, 94, 99, 0.06);
  --shadow-lg: 0 18px 48px rgba(15, 94, 99, 0.16);

  --font-sans: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --font-mono: ui-monospace, "SFMono-Regular", "JetBrains Mono", "Fira Code",
    Menlo, Consolas, "Liberation Mono", monospace;

  --transition: 160ms cubic-bezier(0.4, 0, 0.2, 1);
}

/* ---- Reset / base ------------------------------------------------------- */
*, *::before, *::after { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 1.0625rem;
  line-height: 1.7;
  color: var(--text);
  background: var(--bg);
  background-image:
    radial-gradient(1200px 600px at 100% -10%, var(--teal-50), transparent 60%),
    radial-gradient(900px 500px at -10% 0%, #fff7ed55, transparent 55%);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

img, svg { max-width: 100%; height: auto; }

/* ---- Layout container --------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: clamp(1rem, 4vw, 3rem);
}

main { flex: 1 0 auto; }

/* ---- Links -------------------------------------------------------------- */
a {
  color: var(--link);
  text-decoration: none;
  text-underline-offset: 0.18em;
  transition: color var(--transition), background-color var(--transition);
}
a:hover { color: var(--link-hover); text-decoration: underline; }
a:focus-visible,
button:focus-visible,
summary:focus-visible,
input:focus-visible {
  outline: 3px solid var(--teal-500);
  outline-offset: 2px;
  border-radius: 4px;
}

/* ---- Typography --------------------------------------------------------- */
h1, h2, h3, h4 {
  line-height: 1.25;
  color: var(--text);
  font-weight: 700;
  scroll-margin-top: calc(var(--header-h) + 1rem);
}
h2 { font-size: clamp(1.5rem, 2.4vw, 2rem); margin-top: 2.4em; }
h3 { font-size: clamp(1.2rem, 1.8vw, 1.45rem); margin-top: 1.8em; }
h4 { font-size: 1.1rem; margin-top: 1.4em; }
p { margin: 1em 0; }

/* =========================================================================
   Header
   ========================================================================= */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-h);
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
}
.site-header .container {
  height: 100%;
  display: flex;
  align-items: center;
  gap: 1rem;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--text);
}
.brand:hover { color: var(--primary); text-decoration: none; }
.brand img { width: 2.1rem; height: 2.1rem; filter: drop-shadow(0 2px 4px rgba(15,94,99,.25)); transition: transform var(--transition); }
.brand:hover img { transform: rotate(-6deg) scale(1.05); }
.brand-name { font-size: 1.02rem; }
.brand-name .brand-sub { display: block; font-size: 0.72rem; font-weight: 600; color: var(--text-muted); letter-spacing: 0.02em; }

.nav-toggle {
  margin-left: auto;
  display: none;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.4rem 0.55rem;
  cursor: pointer;
  color: var(--text);
}

.site-nav {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}
.site-nav a {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.45rem 0.8rem;
  border-radius: 999px;
  color: var(--text-soft);
  font-weight: 600;
  font-size: 0.95rem;
}
.site-nav a .icon { color: var(--primary); transition: transform var(--transition); }
.site-nav a:hover { background: var(--teal-50); color: var(--primary); text-decoration: none; }
.site-nav a:hover .icon { transform: translateY(-1px) scale(1.08); }
.site-nav a[aria-current="page"],
.site-nav a.is-active {
  background: var(--teal-600);
  color: #fff;
}
.site-nav a[aria-current="page"] .icon,
.site-nav a.is-active .icon { color: #fff; }

@media (max-width: 820px) {
  .nav-toggle { display: inline-flex; }
  .site-nav {
    position: absolute;
    top: var(--header-h);
    left: 0; right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0.25rem;
    padding: 0.75rem clamp(1rem, 4vw, 3rem) 1rem;
    background: rgba(255,255,255,0.97);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow-md);
    display: none;
  }
  .site-nav.open { display: flex; }
  .site-nav a { border-radius: var(--radius-sm); }
}

/* =========================================================================
   Footer
   ========================================================================= */
.site-footer {
  flex-shrink: 0;
  margin-top: 4rem;
  background: linear-gradient(180deg, var(--surface-2), var(--bg-soft));
  border-top: 1px solid var(--border);
}
.site-footer .container {
  padding-block: 2.5rem;
  display: grid;
  gap: 1.75rem;
  grid-template-columns: 1.3fr repeat(2, 1fr);
}
.footer-brand img { width: 2.4rem; height: 2.4rem; }
.footer-brand p { color: var(--text-muted); font-size: 0.92rem; max-width: 34ch; }
.footer-col h3 { font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.06em; color: var(--text-muted); margin: 0 0 0.7rem; }
.footer-col ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.4rem; }
.footer-col a { color: var(--text-soft); font-size: 0.95rem; }
.footer-col a:hover { color: var(--primary); }
.footer-bottom {
  border-top: 1px solid var(--border);
  background: var(--bg-soft);
}
.footer-bottom .container {
  padding-block: 1rem;
  display: block;
  color: var(--text-muted);
  font-size: 0.85rem;
}
@media (max-width: 720px) {
  .site-footer .container { grid-template-columns: 1fr 1fr; }
  .footer-brand { grid-column: 1 / -1; }
}

/* =========================================================================
   Hero / front page
   ========================================================================= */
.hero {
  text-align: center;
  padding-block: clamp(2.5rem, 6vw, 5rem) clamp(1.5rem, 3vw, 2.5rem);
}
.hero-logo {
  width: clamp(7rem, 16vw, 11rem);
  height: auto;
  margin: 0 auto 1.4rem;
  display: block;
  filter: drop-shadow(0 12px 30px rgba(15, 94, 99, 0.28));
  transition: transform var(--transition);
}
.hero-logo:hover { transform: translateY(-4px) scale(1.03); }
.hero h1 {
  font-size: clamp(2rem, 4.5vw, 3.25rem);
  line-height: 1.1;
  margin: 0 0 0.6rem;
  background: linear-gradient(100deg, var(--teal-700), var(--teal-500) 55%, var(--sky-500));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  letter-spacing: -0.02em;
}
.hero .lead {
  font-size: clamp(1.05rem, 1.6vw, 1.25rem);
  color: var(--text-soft);
  max-width: 60rem;
  margin-inline: auto;
}
.hero-prose { max-width: 62rem; margin: 1.5rem auto 0; text-align: left; color: var(--text-soft); }

/* CTA buttons */
.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
  margin-top: 2rem;
}
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.85rem 1.4rem;
  border-radius: 999px;
  font-weight: 700;
  font-size: 1rem;
  border: 1px solid transparent;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition), box-shadow var(--transition), background-color var(--transition);
}
.btn:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); text-decoration: none; }
.btn .icon { width: 1.35rem; height: 1.35rem; }
.btn-primary { background: linear-gradient(120deg, var(--teal-600), var(--teal-700)); color: #fff; }
.btn-primary:hover { color: #fff; }
.btn-accent  { background: linear-gradient(120deg, var(--amber-400), var(--amber-500)); color: #5a3a00; }
.btn-accent:hover { color: #5a3a00; }
.btn-ghost { background: var(--surface); color: var(--primary); border-color: var(--border-strong); }

.btn .icon.i-layers { color: #fff; }

/* Section / card grid */
.section-head { text-align: center; max-width: 52rem; margin: 3.5rem auto 0; }
.section-head h2 { margin-top: 0; }
.section-head p { color: var(--text-soft); }

.card-grid {
  display: grid;
  gap: 1.5rem;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 22rem), 1fr));
  margin-top: 2rem;
}
.card {
  display: flex;
  flex-direction: column;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); border-color: var(--teal-200); }
.card-icon {
  width: 3rem; height: 3rem;
  display: grid; place-items: center;
  border-radius: 12px;
  margin-bottom: 1rem;
  background: linear-gradient(135deg, var(--teal-50), var(--teal-100));
  color: var(--teal-700);
}
.card h3 { margin: 0 0 0.4rem; font-size: 1.2rem; }
.card h3 a { color: var(--text); }
.card:hover h3 a { color: var(--primary); }
.card p { margin: 0 0 1rem; color: var(--text-soft); font-size: 0.96rem; }
.card .card-links { margin-top: auto; list-style: none; padding: 0; display: grid; gap: 0.35rem; }
.card .card-links a { font-size: 0.92rem; font-weight: 600; display: inline-flex; gap: 0.4rem; align-items: center; }
.card .card-links a::before { content: "→"; color: var(--accent); transition: transform var(--transition); }
.card .card-links a:hover::before { transform: translateX(3px); }

/* =========================================================================
   Article / content page
   ========================================================================= */
.page-wrap { padding-block: 1.5rem 2rem; }

.breadcrumbs {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin: 0.5rem 0 1.25rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  align-items: center;
}
.breadcrumbs ol { list-style: none; display: flex; flex-wrap: wrap; gap: 0.4rem; align-items: center; margin: 0; padding: 0; }
.breadcrumbs li { display: inline-flex; align-items: center; gap: 0.4rem; }
.breadcrumbs li + li::before { content: "/"; color: var(--border-strong); }
.breadcrumbs a { color: var(--text-muted); font-weight: 600; }
.breadcrumbs a:hover { color: var(--primary); }
.breadcrumbs [aria-current="page"] { color: var(--text-soft); }

.prose { max-width: var(--measure); }

/* Colorful page title (first h1 in article) */
.prose h1 {
  font-size: clamp(1.9rem, 3.6vw, 2.8rem);
  line-height: 1.12;
  letter-spacing: -0.02em;
  margin: 0.2rem 0 1rem;
  background: linear-gradient(100deg, var(--teal-700), var(--teal-500) 60%, var(--sky-500));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.prose h2 {
  padding-bottom: 0.3rem;
  border-bottom: 2px solid var(--teal-100);
}
.prose h2::before {
  content: "";
  display: inline-block;
  width: 0.5rem; height: 1.15rem;
  margin-right: 0.55rem;
  vertical-align: -0.12em;
  border-radius: 3px;
  background: linear-gradient(var(--teal-500), var(--teal-700));
}
.prose h3 { color: var(--teal-800); }
.prose :is(h2, h3, h4) a.header-anchor { color: inherit; }
.prose :is(h2, h3, h4) a.header-anchor:hover { text-decoration: none; }
.prose ul, .prose ol { padding-left: 1.4rem; }
.prose li { margin: 0.35em 0; }
.prose li::marker { color: var(--teal-600); }

/* Links inside prose */
.prose a {
  font-weight: 600;
  background-image: linear-gradient(var(--teal-200), var(--teal-200));
  background-size: 0% 2px;
  background-repeat: no-repeat;
  background-position: 0 100%;
  transition: background-size var(--transition), color var(--transition);
}
.prose a:hover { text-decoration: none; background-size: 100% 2px; }

/* Blockquotes */
.prose blockquote {
  margin: 1.5em 0;
  padding: 0.6rem 1.2rem;
  border-left: 4px solid var(--teal-500);
  background: var(--teal-50);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--text-soft);
}

/* ---- Inline code -------------------------------------------------------- */
.prose :not(pre) > code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--code-inline-bg);
  color: #0c4a44;
  padding: 0.12em 0.4em;
  border-radius: 6px;
  border: 0;
  word-break: break-word;
}

/* ---- Code blocks + copy button ----------------------------------------- */
.code-block {
  position: relative;
  margin: 1.5em 0;
}
.code-block pre[class*="language-"] {
  margin: 0;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: var(--radius-sm);
  padding: 1rem 1.1rem;
  overflow-x: auto;
  font-size: 0.9rem;
  line-height: 1.6;
  box-shadow: var(--shadow-sm);
}
.prose pre[class*="language-"] code {
  font-family: var(--font-mono);
  background: none;
  color: var(--code-text);
  padding: 0;
  font-size: inherit;
}
.copy-btn {
  position: absolute;
  top: 0.55rem;
  right: 0.55rem;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-soft);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 7px;
  padding: 0.28rem 0.55rem;
  cursor: pointer;
  opacity: 0;
  transition: opacity var(--transition), background-color var(--transition), color var(--transition);
}
.code-block:hover .copy-btn,
.copy-btn:focus-visible { opacity: 1; }
.copy-btn:hover { background: var(--teal-600); color: #fff; border-color: var(--teal-600); }
.copy-btn.copied { background: var(--teal-600); color: #fff; border-color: var(--teal-600); }
.copy-btn svg { width: 0.95rem; height: 0.95rem; }

/* Prism token colors — light theme matched to palette */
.token.comment, .token.prolog, .token.doctype, .token.cdata { color: #7c8d89; font-style: italic; }
.token.punctuation { color: #54716c; }
.token.property, .token.tag, .token.boolean, .token.number,
.token.constant, .token.symbol, .token.deleted { color: #b4530a; }
.token.selector, .token.attr-name, .token.string, .token.char,
.token.builtin, .token.inserted { color: #0f766e; }
.token.operator, .token.entity, .token.url,
.language-css .token.string, .style .token.string { color: #0369a1; }
.token.atrule, .token.attr-value, .token.keyword { color: #7c3aed; }
.token.function, .token.class-name { color: #c2410c; }
.token.regex, .token.important, .token.variable { color: #be123c; }
.token.important, .token.bold { font-weight: 700; }
.token.italic { font-style: italic; }

/* ---- Tables (responsive scroll) ---------------------------------------- */
.table-wrap {
  overflow-x: auto;
  margin: 1.5em 0;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-sm);
  -webkit-overflow-scrolling: touch;
}
.prose table {
  border-collapse: collapse;
  width: 100%;
  min-width: 32rem;
  font-size: 0.94rem;
}
.prose thead { background: linear-gradient(var(--teal-600), var(--teal-700)); }
.prose th {
  color: #fff;
  text-align: left;
  font-weight: 700;
  padding: 0.7rem 0.9rem;
  white-space: nowrap;
}
.prose td { padding: 0.65rem 0.9rem; border-top: 1px solid var(--border); vertical-align: top; }
.prose tbody tr:nth-child(even) { background: var(--surface-2); }
.prose tbody tr:hover { background: var(--teal-50); }

/* ---- Task-list checkboxes ---------------------------------------------- */
.prose ul.contains-task-list { list-style: none; padding-left: 0.2rem; }
.prose li.task-list-item { display: flex; align-items: flex-start; gap: 0.6rem; }
.prose li.task-list-item::marker { content: ""; }
.prose li.task-list-item input.task-list-item-checkbox {
  appearance: none;
  -webkit-appearance: none;
  flex: 0 0 auto;
  width: 1.2rem; height: 1.2rem;
  margin-top: 0.28rem;
  border: 2px solid var(--border-strong);
  border-radius: 6px;
  background: var(--surface);
  cursor: pointer;
  display: grid;
  place-content: center;
  transition: background-color var(--transition), border-color var(--transition);
}
.prose li.task-list-item input.task-list-item-checkbox:hover { border-color: var(--teal-500); }
.prose li.task-list-item input.task-list-item-checkbox::after {
  content: "";
  width: 0.65rem; height: 0.65rem;
  transform: scale(0);
  transform-origin: center;
  transition: transform var(--transition);
  box-shadow: inset 1rem 1rem #fff;
  clip-path: polygon(14% 44%, 0 65%, 50% 100%, 100% 16%, 80% 0%, 43% 62%);
}
.prose li.task-list-item input.task-list-item-checkbox:checked {
  background: var(--teal-600);
  border-color: var(--teal-600);
}
.prose li.task-list-item input.task-list-item-checkbox:checked::after { transform: scale(1); }
.prose li.task-list-item input.task-list-item-checkbox:checked + label,
.prose li.task-list-item.is-checked > label { text-decoration: line-through; color: var(--text-muted); }

/* ---- FAQ accordions ----------------------------------------------------- */
.prose details.faq {
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  margin: 0.75rem 0;
  background: var(--surface);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
}
.prose details.faq + details.faq { margin-top: 0.6rem; }
.prose details.faq > summary {
  list-style: none;
  cursor: pointer;
  padding: 0.95rem 1.1rem;
  font-weight: 700;
  color: var(--teal-800);
  display: flex;
  align-items: center;
  gap: 0.6rem;
  background: var(--surface-2);
}
.prose details.faq > summary::-webkit-details-marker { display: none; }
.prose details.faq > summary::before {
  content: "";
  width: 0.6rem; height: 0.6rem;
  border-right: 2px solid var(--teal-600);
  border-bottom: 2px solid var(--teal-600);
  transform: rotate(-45deg);
  transition: transform var(--transition);
  flex: 0 0 auto;
}
.prose details.faq[open] > summary::before { transform: rotate(45deg); }
.prose details.faq > summary:hover { background: var(--teal-50); }
.prose details.faq .faq-body { padding: 0.4rem 1.1rem 1.1rem; }
.prose details.faq .faq-body > :first-child { margin-top: 0; }

/* ---- Mermaid (figures + click-to-fullscreen) --------------------------- */
.diagram-figure {
  margin: 1.75em 0;
}
.mermaid {
  position: relative;
  margin: 0;
  text-align: center;
  background:
    radial-gradient(120% 120% at 0 0, var(--teal-50), transparent 55%),
    var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.25rem 1.5rem;
  box-shadow: var(--shadow-sm);
  overflow-x: auto;
  transition: box-shadow var(--transition), border-color var(--transition);
}
.mermaid svg { max-width: 100%; height: auto; }
.mermaid:not([data-processed]) { color: transparent; min-height: 2rem; }
.mermaid.is-rendered { cursor: zoom-in; }
.mermaid.is-rendered:hover { box-shadow: var(--shadow-md); border-color: var(--teal-200); }

/* "Expand" affordance shown on hover/focus */
.diagram-expand {
  position: absolute;
  top: 0.6rem;
  right: 0.6rem;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font: 600 0.75rem/1 var(--font-sans);
  color: var(--text-soft);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 7px;
  padding: 0.3rem 0.5rem;
  cursor: zoom-in;
  opacity: 0;
  transition: opacity var(--transition), background-color var(--transition), color var(--transition);
}
.mermaid.is-rendered:hover .diagram-expand,
.diagram-expand:focus-visible { opacity: 1; }
.diagram-expand:hover { background: var(--teal-600); color: #fff; border-color: var(--teal-600); }
.diagram-expand svg { width: 0.95rem; height: 0.95rem; }

.diagram-figure figcaption {
  margin-top: 0.6rem;
  text-align: center;
  font-size: 0.88rem;
  color: var(--text-muted);
  font-style: italic;
}

/* Fullscreen lightbox */
.diagram-lightbox {
  position: fixed;
  inset: 0;
  z-index: 200;
  display: none;
  align-items: center;
  justify-content: center;
  padding: clamp(1rem, 4vw, 3rem);
  background: rgba(8, 24, 22, 0.82);
  backdrop-filter: blur(6px);
}
.diagram-lightbox.open { display: flex; }
.diagram-lightbox .lb-stage {
  background: var(--surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  max-width: 96vw;
  max-height: 90vh;
  overflow: auto;
  padding: clamp(1rem, 3vw, 2.25rem);
  -webkit-overflow-scrolling: touch;
}
.diagram-lightbox .lb-stage svg {
  display: block;
  margin: auto;
  height: auto;
  max-width: none; /* allow scaling beyond container for true large view */
}
.diagram-lightbox .lb-toolbar {
  position: fixed;
  top: 1rem;
  right: 1rem;
  display: flex;
  gap: 0.5rem;
}
.lb-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.6rem;
  height: 2.6rem;
  border-radius: 10px;
  border: 1px solid rgba(255, 255, 255, 0.25);
  background: rgba(255, 255, 255, 0.12);
  color: #fff;
  font-size: 1.1rem;
  font-weight: 700;
  cursor: pointer;
  transition: background-color var(--transition), transform var(--transition);
}
.lb-btn:hover { background: rgba(255, 255, 255, 0.28); transform: translateY(-1px); }
.lb-btn svg { width: 1.2rem; height: 1.2rem; }
.diagram-lightbox .lb-hint {
  position: fixed;
  bottom: 1rem;
  left: 50%;
  transform: translateX(-50%);
  color: rgba(255, 255, 255, 0.78);
  font-size: 0.8rem;
}
body.lb-open { overflow: hidden; }

/* ---- KaTeX -------------------------------------------------------------- */
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 0.4rem 0; }

/* ---- Related pages / child listing ------------------------------------- */
.child-pages {
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 2px solid var(--teal-100);
}
.child-pages h2 { margin-top: 0; }
.related-grid {
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 18rem), 1fr));
}
.related-card {
  display: block;
  padding: 1rem 1.1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.related-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: var(--teal-200); text-decoration: none; }
.related-card .rc-title { font-weight: 700; color: var(--text); }
.related-card:hover .rc-title { color: var(--primary); }
.related-card .rc-arrow { color: var(--accent); }

/* ---- Page navigation footer (prev section link) ------------------------- */
.page-foot-nav {
  margin-top: 2.5rem;
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}
.page-foot-nav a {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 600;
  padding: 0.5rem 0.9rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
}
.page-foot-nav a:hover { background: var(--teal-50); text-decoration: none; }

/* ---- Skip link ---------------------------------------------------------- */
.skip-link {
  position: absolute;
  left: 0.5rem;
  top: -3rem;
  background: var(--teal-700);
  color: #fff;
  padding: 0.5rem 0.9rem;
  border-radius: 8px;
  z-index: 100;
  transition: top var(--transition);
}
.skip-link:focus { top: 0.5rem; color: #fff; }

/* ---- Reduced motion ----------------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
  }
}