/* =========================================================================
   Grant Automation — light, professional theme
   ========================================================================= */

:root {
  /* Palette */
  --primary: #1f6f8b;
  --primary-dark: #155a73;
  --primary-soft: #e7f1f5;
  --accent: #e76f51;   /* coral  */
  --accent-2: #e9b949; /* amber  */
  --accent-3: #2a9d8f; /* green  */

  --ink: #1c2b33;
  --ink-soft: #4a5b66;
  --ink-faint: #6a8693;

  --bg: #f4f8fa;
  --bg-2: #eaf2f5;
  --surface: #ffffff;
  --border: #d8e3e9;
  --border-soft: #e7eef2;

  --code-bg: #f3f7f9;
  --inline-code-bg: rgba(31, 111, 139, 0.09);

  /* Type */
  --font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: "SFMono-Regular", "JetBrains Mono", "Fira Code", Consolas, "Liberation Mono", Menlo, monospace;

  /* Metrics */
  --header-h: 64px;
  --container: 90rem;     /* wide desktop shell */
  --measure: 80rem;       /* prose width — wide, not a narrow column */
  --radius: 12px;
  --radius-sm: 8px;
  --shadow-sm: 0 1px 2px rgba(20, 50, 65, 0.06), 0 2px 8px rgba(20, 50, 65, 0.05);
  --shadow-md: 0 6px 24px rgba(20, 50, 65, 0.10);
  --transition: 180ms ease;
}

/* ---- Reset / base ------------------------------------------------------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: clamp(1rem, 0.96rem + 0.2vw, 1.0625rem);
  line-height: 1.7;
  color: var(--ink);
  background: var(--bg);
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
img, svg { max-width: 100%; height: auto; }
a { color: var(--primary); text-decoration: none; }

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--primary);
  color: #fff;
  padding: 0.6rem 1rem;
  border-radius: 0 0 var(--radius-sm) 0;
  z-index: 200;
}
.skip-link:focus { left: 0; }

/* ---- Header ------------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.86);
  backdrop-filter: saturate(160%) blur(10px);
  border-bottom: 1px solid var(--border);
}
.site-header__inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 clamp(1rem, 3vw, 2rem);
  height: var(--header-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}
.brand { display: flex; align-items: center; gap: 0.6rem; }
.brand__logo { transition: transform var(--transition); }
.brand:hover .brand__logo { transform: rotate(-6deg) scale(1.05); }
.brand__text { display: flex; flex-direction: column; line-height: 1.15; }
.brand__name { font-weight: 700; color: var(--ink); font-size: 1.02rem; letter-spacing: -0.01em; }
.brand__tag { font-size: 0.72rem; color: var(--ink-faint); font-weight: 600; letter-spacing: 0.06em; }

.primary-nav__list {
  list-style: none;
  display: flex;
  gap: 0.35rem;
  margin: 0;
  padding: 0;
}
.nav-link {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.5rem 0.8rem;
  border-radius: 999px;
  color: var(--ink-soft);
  font-weight: 600;
  font-size: 0.92rem;
  transition: background var(--transition), color var(--transition);
  white-space: nowrap;
}
.nav-link:hover { background: var(--primary-soft); color: var(--primary-dark); }
.nav-link.is-current { background: var(--primary); color: #fff; }
.nav-link.is-current .nav-icon { stroke: #fff; }
.nav-icon {
  width: 18px; height: 18px;
  fill: none;
  stroke: var(--primary);
  stroke-width: 1.9;
  stroke-linecap: round;
  stroke-linejoin: round;
  flex: none;
}
.nav-icon--blue { stroke: var(--primary); }
.nav-icon--amber { stroke: var(--accent-2); }
.nav-icon--green { stroke: var(--accent-3); }

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: 0;
  padding: 8px;
  cursor: pointer;
}
.nav-toggle__bar {
  width: 24px; height: 2.5px;
  background: var(--ink);
  border-radius: 2px;
  transition: transform var(--transition), opacity var(--transition);
}
.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(1) { transform: translateY(7.5px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(3) { transform: translateY(-7.5px) rotate(-45deg); }

/* ---- Main / footer scaffolding ----------------------------------------- */
.site-main {
  flex: 1 0 auto;
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding: clamp(1.5rem, 4vw, 3rem) clamp(1rem, 3vw, 2rem);
}

.site-footer {
  flex-shrink: 0;
  background: var(--ink);
  color: #cddbe2;
  margin-top: 3rem;
}
.site-footer__inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 2.5rem clamp(1rem, 3vw, 2rem) 1.5rem;
  display: flex;
  flex-wrap: wrap;
  gap: 2rem;
  justify-content: space-between;
}
.site-footer__brand { display: flex; align-items: center; gap: 0.8rem; }
.site-footer__brand img { background: #fff; border-radius: 10px; padding: 4px; }
.site-footer__name { margin: 0; font-weight: 700; color: #fff; }
.site-footer__desc { margin: 0; font-size: 0.85rem; color: #93a8b2; }
.site-footer__heading { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.08em; color: #7e96a1; margin: 0 0 0.6rem; }
.site-footer__nav ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.4rem; }
.site-footer__nav a { color: #cddbe2; transition: color var(--transition); }
.site-footer__nav a:hover { color: #fff; text-decoration: underline; }
.site-footer__bar {
  border-top: 1px solid rgba(255,255,255,0.12);
  text-align: center;
  font-size: 0.8rem;
  color: #8aa0aa;
  padding: 1rem;
}

/* ---- Typography --------------------------------------------------------- */
h1, h2, h3, h4 { line-height: 1.25; color: var(--ink); font-weight: 700; letter-spacing: -0.015em; scroll-margin-top: calc(var(--header-h) + 1rem); }
h2, h3, h4 { scroll-margin-top: calc(var(--header-h) + 1rem); }
p, ul, ol, table, pre, .table-scroll { scroll-margin-top: calc(var(--header-h) + 1rem); }

.doc__body h1 {
  font-size: clamp(1.9rem, 1.4rem + 2.2vw, 2.8rem);
  background: linear-gradient(120deg, var(--primary-dark), var(--accent-3) 70%, var(--primary));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  margin: 0.2rem 0 1.2rem;
}
.doc__body h2 {
  font-size: clamp(1.4rem, 1.1rem + 1vw, 1.85rem);
  margin: 2.4rem 0 0.9rem;
  padding-bottom: 0.4rem;
  border-bottom: 2px solid var(--border);
  color: var(--primary-dark);
}
.doc__body h3 {
  font-size: clamp(1.15rem, 1rem + 0.5vw, 1.4rem);
  margin: 1.8rem 0 0.7rem;
  color: var(--accent-3);
}
.doc__body h4 { font-size: 1.08rem; margin: 1.4rem 0 0.5rem; color: var(--ink-soft); }
.doc__body p { margin: 0 0 1.15rem; }
.doc__body strong { color: var(--ink); }

/* Header anchor link */
.header-anchor {
  text-decoration: none;
  color: var(--accent-2);
  opacity: 0;
  margin-left: -1.1em;
  padding-right: 0.35em;
  transition: opacity var(--transition);
}
h1:hover .header-anchor, h2:hover .header-anchor, h3:hover .header-anchor, h4:hover .header-anchor { opacity: 1; }

/* Links inside content */
.doc__body a, .hero__intro a {
  color: var(--primary);
  text-decoration: none;
  background-image: linear-gradient(var(--accent-2), var(--accent-2));
  background-size: 0% 2px;
  background-repeat: no-repeat;
  background-position: 0 100%;
  transition: background-size var(--transition), color var(--transition);
  font-weight: 500;
}
.doc__body a:hover { color: var(--primary-dark); background-size: 100% 2px; }

/* ---- Inline code -------------------------------------------------------- */
:not(pre) > code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--inline-code-bg);
  color: var(--primary-dark);
  padding: 0.12em 0.4em;
  border-radius: 5px;
}

/* ---- Code blocks -------------------------------------------------------- */
.code-block {
  margin: 1.4rem 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--code-bg);
  box-shadow: var(--shadow-sm);
}
.code-block__bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.45rem 0.75rem 0.45rem 1rem;
  background: var(--bg-2);
  border-bottom: 1px solid var(--border);
}
.code-block__lang {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-faint);
}
.copy-btn {
  font: inherit;
  font-size: 0.74rem;
  font-weight: 600;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--ink-soft);
  padding: 0.25rem 0.7rem;
  border-radius: 999px;
  cursor: pointer;
  transition: all var(--transition);
}
.copy-btn:hover { border-color: var(--primary); color: var(--primary); }
.copy-btn.is-copied { background: var(--accent-3); border-color: var(--accent-3); color: #fff; }
.code-block pre {
  margin: 0;
  padding: 1.1rem 1.2rem;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.86rem;
  line-height: 1.65;
  background: var(--code-bg);
  color: #243b44;
}
.code-block code { font-family: inherit; background: none; padding: 0; color: inherit; }

/* ---- Prism light token theme (matches palette) ------------------------- */
.token.comment, .token.prolog, .token.doctype, .token.cdata { color: #7c95a0; font-style: italic; }
.token.punctuation { color: #5a6b74; }
.token.property, .token.tag, .token.boolean, .token.number, .token.constant, .token.symbol { color: #b5651d; }
.token.selector, .token.attr-name, .token.string, .token.char, .token.builtin, .token.inserted { color: #2a8a7c; }
.token.operator, .token.entity, .token.url, .language-css .token.string, .style .token.string { color: #5a6b74; }
.token.atrule, .token.attr-value, .token.keyword { color: var(--primary-dark); font-weight: 600; }
.token.function, .token.class-name { color: #c0562f; }
.token.regex, .token.important, .token.variable { color: #b07b00; }
.token.important, .token.bold { font-weight: 700; }
.token.italic { font-style: italic; }
/* JSON keys */
.language-json .token.property { color: var(--primary-dark); }

/* ---- Tables ------------------------------------------------------------- */
.table-scroll {
  overflow-x: auto;
  margin: 1.4rem 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  -webkit-overflow-scrolling: touch;
}
.table-scroll table { border-collapse: collapse; width: 100%; min-width: 32rem; font-size: 0.92rem; }
.table-scroll th, .table-scroll td { padding: 0.65rem 0.9rem; text-align: left; border-bottom: 1px solid var(--border-soft); }
.table-scroll thead th { background: var(--primary-soft); color: var(--primary-dark); font-weight: 700; }
.table-scroll tbody tr:nth-child(even) { background: var(--bg); }
.table-scroll tbody tr:hover { background: var(--primary-soft); }

/* ---- Blockquote / lists ------------------------------------------------- */
.doc__body blockquote {
  margin: 1.4rem 0;
  padding: 0.6rem 1.2rem;
  border-left: 4px solid var(--accent-2);
  background: var(--bg-2);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--ink-soft);
}
.doc__body ul, .doc__body ol { padding-left: 1.4rem; margin: 0 0 1.15rem; }
.doc__body li { margin: 0.3rem 0; }

/* ---- Task list checkboxes ---------------------------------------------- */
ul.contains-task-list, .contains-task-list ul.contains-task-list { list-style: none; padding-left: 0.25rem; }
.task-list-item { display: flex; align-items: flex-start; gap: 0.6rem; margin: 0.5rem 0; }
.task-list-item::marker { content: ""; }
.task-list-item-checkbox {
  appearance: none;
  -webkit-appearance: none;
  width: 1.15em; height: 1.15em;
  margin-top: 0.28em;
  border: 2px solid var(--primary);
  border-radius: 5px;
  flex: none;
  cursor: pointer;
  position: relative;
  transition: background var(--transition), border-color var(--transition);
}
.task-list-item-checkbox:checked { background: var(--accent-3); border-color: var(--accent-3); }
.task-list-item-checkbox:checked::after {
  content: "";
  position: absolute;
  left: 0.32em; top: 0.08em;
  width: 0.28em; height: 0.55em;
  border: solid #fff;
  border-width: 0 2.5px 2.5px 0;
  transform: rotate(45deg);
}
.task-list-item-checkbox:checked + label,
.task-list-item-checkbox:checked ~ label { text-decoration: line-through; color: var(--ink-faint); }
.task-list-item label { cursor: pointer; }

/* ---- FAQ accordions ----------------------------------------------------- */
.faq details, details.faq-item {
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  margin: 0.7rem 0;
  background: var(--surface);
  overflow: hidden;
}
.faq summary, details.faq-item > summary {
  cursor: pointer;
  padding: 0.9rem 1.1rem;
  font-weight: 600;
  color: var(--primary-dark);
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}
.faq summary::-webkit-details-marker, details.faq-item > summary::-webkit-details-marker { display: none; }
.faq summary::after, details.faq-item > summary::after { content: "+"; font-size: 1.4rem; color: var(--accent); transition: transform var(--transition); }
.faq details[open] summary::after, details.faq-item[open] > summary::after { transform: rotate(45deg); }
.faq details > *:not(summary), details.faq-item > *:not(summary) { padding: 0 1.1rem 1rem; margin: 0; }

/* ---- Breadcrumbs -------------------------------------------------------- */
.breadcrumbs ol {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  padding: 0;
  margin: 0 0 1.5rem;
  font-size: 0.85rem;
  color: var(--ink-faint);
}
.breadcrumbs li { display: flex; align-items: center; gap: 0.35rem; }
.breadcrumbs li + li::before { content: "/"; color: var(--border); }
.breadcrumbs a { color: var(--ink-soft); transition: color var(--transition); }
.breadcrumbs a:hover { color: var(--primary); }
.breadcrumbs [aria-current="page"] { color: var(--ink); font-weight: 600; }

/* ---- Doc wrapper width -------------------------------------------------- */
.doc { max-width: var(--measure); margin: 0 auto; }
.doc__body { font-size: 1.04rem; }

/* ---- Related / cards ---------------------------------------------------- */
.related { margin-top: 3rem; padding-top: 1.5rem; border-top: 1px solid var(--border); }
.related__title { font-size: 1.2rem; color: var(--primary-dark); margin: 0 0 1rem; }
.card-grid {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 22rem), 1fr));
}
.card-grid--compact { grid-template-columns: repeat(auto-fill, minmax(min(100%, 18rem), 1fr)); }
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: var(--primary); }
.card a {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.8rem;
  padding: 1rem 1.2rem;
  font-weight: 600;
  color: var(--ink);
}
.card__arrow { color: var(--accent); transition: transform var(--transition); }
.card:hover .card__arrow { transform: translateX(4px); }

/* ---- Home: hero --------------------------------------------------------- */
.hero { text-align: center; padding: 1rem 0 2rem; }
.hero__logo-wrap { display: block; margin: 0 auto 1.2rem; }
.hero__logo { width: clamp(110px, 18vw, 168px); height: auto; filter: drop-shadow(0 8px 20px rgba(31,111,139,0.22)); transition: transform 240ms ease; }
.hero__logo:hover { transform: translateY(-4px) scale(1.03); }
.hero__title {
  font-size: clamp(2rem, 1.4rem + 3vw, 3.4rem);
  margin: 0 auto 1rem;
  max-width: 20ch;
  letter-spacing: -0.02em;
}
.hero__accent {
  background: linear-gradient(120deg, var(--primary), var(--accent-3));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero__lede {
  font-size: clamp(1.1rem, 1rem + 0.6vw, 1.3rem);
  color: var(--ink-soft);
  max-width: 52rem;
  margin: 0 auto 1.5rem;
}
.hero__intro { max-width: var(--measure); margin: 0 auto 2rem; text-align: left; }
.hero__intro p { margin: 0 0 1rem; color: var(--ink-soft); }

.hero__ctas {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 1rem;
}
.cta {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.85rem 1.3rem;
  border-radius: 999px;
  font-weight: 700;
  color: #fff;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition), box-shadow var(--transition), filter var(--transition);
}
.cta .nav-icon { width: 22px; height: 22px; stroke: #fff; }
.cta:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); filter: brightness(1.04); }
.cta--1 { background: linear-gradient(135deg, var(--primary), var(--primary-dark)); }
.cta--2 { background: linear-gradient(135deg, #e9a93a, var(--accent)); }
.cta--3 { background: linear-gradient(135deg, var(--accent-3), #1f8b6f); }

/* ---- Home: section cards ----------------------------------------------- */
.sections { margin-top: 3.5rem; }
.sections__head { text-align: center; max-width: 50rem; margin: 0 auto 2rem; }
.sections__head h2 { font-size: clamp(1.6rem, 1.3rem + 1vw, 2.1rem); color: var(--primary-dark); margin: 0 0 0.5rem; }
.sections__head p { color: var(--ink-soft); margin: 0; }

.section-card {
  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-top: 4px solid var(--primary);
}
.section-card--2 { border-top-color: var(--accent-2); }
.section-card--3 { border-top-color: var(--accent-3); }
.section-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); }
.section-card__icon {
  width: 48px; height: 48px;
  display: grid; place-items: center;
  border-radius: 12px;
  background: var(--primary-soft);
  margin-bottom: 0.9rem;
}
.section-card__icon .nav-icon { width: 26px; height: 26px; }
.section-card h3 { margin: 0 0 0.8rem; font-size: 1.2rem; }
.section-card h3 a { color: var(--ink); transition: color var(--transition); }
.section-card h3 a:hover { color: var(--primary); }
.section-card__links { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.45rem; }
.section-card__links a {
  display: inline-block;
  color: var(--ink-soft);
  font-size: 0.93rem;
  transition: color var(--transition), padding var(--transition);
}
.section-card__links a::before { content: "›"; color: var(--accent); margin-right: 0.4rem; }
.section-card__links a:hover { color: var(--primary); padding-left: 3px; }

/* ---- Mermaid diagrams + click-to-enlarge -------------------------------- */
pre.mermaid {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem;
  text-align: center;
  overflow-x: auto;
  /* hide the raw mermaid source until it is rendered into SVG */
  color: transparent;
  min-height: 2rem;
}
pre.mermaid[data-processed="true"] { color: inherit; }

/* Figure wrapper added around each rendered diagram */
.diagram {
  margin: 1.6rem 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
}
.diagram__frame {
  position: relative;
  display: block;
  width: 100%;
  margin: 0;
  padding: 1.25rem 1.25rem 1.5rem;
  background: none;
  border: 0;
  cursor: zoom-in;
  text-align: center;
  font: inherit;
  color: inherit;
}
.diagram__frame svg { max-width: 100%; height: auto; }
.diagram__hint {
  position: absolute;
  top: 0.6rem;
  right: 0.7rem;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--ink-faint);
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.2rem 0.6rem;
  opacity: 0;
  transition: opacity var(--transition), color var(--transition), border-color var(--transition);
}
.diagram__frame:hover .diagram__hint,
.diagram__frame:focus-visible .diagram__hint { opacity: 1; color: var(--primary); border-color: var(--primary); }
.diagram__caption {
  margin: 0;
  padding: 0.6rem 1rem;
  font-size: 0.82rem;
  color: var(--ink-faint);
  text-align: center;
  border-top: 1px solid var(--border-soft);
  background: var(--bg);
}

/* Full-screen lightbox */
.lightbox {
  position: fixed;
  inset: 0;
  z-index: 1000;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  padding: clamp(1rem, 3vw, 2.5rem);
  background: rgba(16, 32, 40, 0.86);
  backdrop-filter: blur(4px);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--transition), visibility var(--transition);
}
.lightbox.is-open { opacity: 1; visibility: visible; }
.lightbox__stage {
  flex: 1 1 auto;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100%;
  min-height: 0;
}
.lightbox__stage svg {
  width: auto;
  height: auto;
  max-width: 96vw;
  max-height: 82vh;
  background: var(--surface);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5);
}
.lightbox__caption { color: #e7eef2; font-size: 0.95rem; text-align: center; max-width: 70ch; margin: 0; }
.lightbox__close {
  position: absolute;
  top: clamp(0.8rem, 2vw, 1.4rem);
  right: clamp(0.8rem, 2vw, 1.4rem);
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  border: 1px solid rgba(255, 255, 255, 0.3);
  background: rgba(255, 255, 255, 0.12);
  color: #fff;
  font-size: 1.5rem;
  line-height: 1;
  cursor: pointer;
  transition: background var(--transition), transform var(--transition);
}
.lightbox__close:hover { background: rgba(255, 255, 255, 0.25); transform: rotate(90deg); }
body.lightbox-open { overflow: hidden; }

/* ---- KaTeX -------------------------------------------------------------- */
.katex { font-size: 1.05em; }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 0.4rem 0; }

/* ---- Responsive --------------------------------------------------------- */
@media (max-width: 820px) {
  .nav-toggle { display: flex; }
  .primary-nav {
    position: fixed;
    inset: var(--header-h) 0 auto 0;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow-md);
    transform: translateY(-120%);
    transition: transform 240ms ease;
    max-height: calc(100vh - var(--header-h));
    overflow-y: auto;
  }
  .primary-nav.is-open { transform: translateY(0); }
  .primary-nav__list { flex-direction: column; gap: 0.2rem; padding: 0.8rem clamp(1rem, 3vw, 2rem) 1.2rem; }
  .nav-link { width: 100%; }
}

/* Widescreen: use more of the available real estate. */
@media (min-width: 1600px) {
  :root { --container: 100rem; --measure: 88rem; }
}
@media (min-width: 2000px) {
  :root { --container: 112rem; --measure: 96rem; }
}

@media (prefers-reduced-motion: reduce) {
  * { scroll-behavior: auto !important; transition: none !important; animation: none !important; }
}