/* ==========================================================================
   Privacy-Preserving Spatial Analytics — site stylesheet
   Light, professional palette: deep teal, indigo, sand, coral accent.
   ========================================================================== */

:root {
  /* Palette */
  --c-bg:           #f7f5f1;
  --c-bg-soft:      #fbfaf6;
  --c-surface:      #ffffff;
  --c-ink:          #1b2230;
  --c-ink-soft:     #475066;
  --c-muted:        #7a8295;

  --c-teal:         #0e7c7b;
  --c-teal-deep:    #075c5b;
  --c-indigo:       #3949ab;
  --c-violet:       #7e3ff2;
  --c-coral:        #e26d5c;
  --c-sand:         #f6c14a;
  --c-mint:         #76c7b8;

  --c-link:         #0e7c7b;
  --c-link-hover:   #7e3ff2;

  --c-border:       #e3dfd6;
  --c-border-soft:  #ece8de;
  --c-code-bg:      #f3eee2;
  --c-code-inline-bg: rgba(14, 124, 123, 0.08);

  --shadow-sm: 0 1px 2px rgba(15, 22, 38, 0.06);
  --shadow-md: 0 6px 18px rgba(15, 22, 38, 0.08);
  --shadow-lg: 0 18px 38px rgba(15, 22, 38, 0.12);

  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;

  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.5rem;
  --space-6: 2rem;
  --space-7: 3rem;
  --space-8: 4rem;

  --header-h: 64px;

  --maxw: 1720px;
  --maxw-narrow: 1480px;
  --measure: 78ch;

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

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-h) + 24px);
  -webkit-text-size-adjust: 100%;
  background: var(--c-bg);
}
body {
  scroll-padding-top: calc(var(--header-h) + 24px);
}

body {
  margin: 0;
  font-family: var(--font-sans);
  color: var(--c-ink);
  background: var(--c-bg);
  font-size: 17px;
  line-height: 1.65;
  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(--c-link);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 140ms ease, border-color 140ms ease;
}
a:hover, a:focus-visible {
  color: var(--c-link-hover);
  border-bottom-color: currentColor;
}

:focus-visible {
  outline: 3px solid rgba(126, 63, 242, 0.45);
  outline-offset: 3px;
  border-radius: 4px;
}

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

.container {
  width: 100%;
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 clamp(1rem, 3vw, 2.25rem);
}
.container--narrow {
  max-width: var(--maxw-narrow);
}

/* ---------- Skip link ---------- */

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--c-ink);
  color: #fff;
  padding: var(--space-3) var(--space-4);
  border-radius: 0 0 var(--radius-sm) 0;
  z-index: 9999;
}
.skip-link:focus {
  left: 0;
}

/* ---------- Header ---------- */

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: saturate(140%) blur(10px);
  -webkit-backdrop-filter: saturate(140%) blur(10px);
  border-bottom: 1px solid var(--c-border-soft);
}
.site-header__inner {
  display: flex;
  align-items: center;
  gap: var(--space-5);
  height: 100%;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  font-weight: 700;
  color: var(--c-ink);
  border-bottom: 0;
}
.brand:hover {
  color: var(--c-teal);
}
.brand__mark {
  width: 36px;
  height: 36px;
  flex: 0 0 36px;
}
.brand__text {
  font-size: 1.02rem;
  letter-spacing: -0.01em;
  white-space: nowrap;
}
.brand__text .brand__text--short {
  display: none;
}

.site-nav {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}
.site-nav a {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: 0.5rem 0.9rem;
  border-radius: var(--radius-sm);
  font-weight: 500;
  font-size: 0.95rem;
  color: var(--c-ink-soft);
  border-bottom: 0;
  transition: background 140ms ease, color 140ms ease, transform 140ms ease;
}
.site-nav a:hover,
.site-nav a:focus-visible {
  background: rgba(14, 124, 123, 0.10);
  color: var(--c-teal-deep);
  transform: translateY(-1px);
}
.site-nav a.is-current {
  background: linear-gradient(135deg, rgba(14, 124, 123, 0.16), rgba(126, 63, 242, 0.12));
  color: var(--c-teal-deep);
}
.site-nav a svg {
  width: 18px;
  height: 18px;
  flex: 0 0 18px;
}

/* Mobile nav toggle */
.nav-toggle {
  display: none;
  margin-left: auto;
  background: none;
  border: 1px solid var(--c-border);
  border-radius: var(--radius-sm);
  padding: 0.45rem 0.6rem;
  cursor: pointer;
  color: var(--c-ink);
}

/* ---------- Footer ---------- */

.site-footer {
  margin-top: auto;
  background: linear-gradient(180deg, var(--c-bg) 0%, #efeadd 100%);
  border-top: 1px solid var(--c-border-soft);
  padding: var(--space-7) 0 var(--space-6);
  color: var(--c-ink-soft);
  font-size: 0.95rem;
}
.site-footer__cols {
  display: grid;
  grid-template-columns: minmax(220px, 1fr) repeat(3, minmax(180px, 1fr));
  gap: var(--space-6);
}
.site-footer h4 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--c-muted);
  margin: 0 0 var(--space-3);
}
.site-footer ul {
  list-style: none;
  margin: 0;
  padding: 0;
}
.site-footer li + li {
  margin-top: var(--space-2);
}
.site-footer a {
  color: var(--c-ink);
}
.site-footer__brand {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}
.site-footer__brand img {
  width: 56px;
  height: 56px;
}
.site-footer__bottom {
  margin-top: var(--space-6);
  border-top: 1px solid var(--c-border-soft);
  padding-top: var(--space-4);
  font-size: 0.85rem;
  color: var(--c-muted);
  display: flex;
  justify-content: space-between;
  gap: var(--space-4);
  flex-wrap: wrap;
}

/* ---------- Main ---------- */

main {
  flex: 1 0 auto;
  padding: clamp(1.5rem, 4vw, 3rem) 0 var(--space-8);
}

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

.hero {
  text-align: center;
  padding: clamp(2rem, 6vw, 4.5rem) 0 var(--space-7);
}
.hero__logo {
  display: block;
  margin: 0 auto var(--space-5);
  width: clamp(140px, 22vw, 220px);
  height: auto;
  filter: drop-shadow(0 12px 24px rgba(57, 73, 171, 0.18));
}
.hero h1 {
  font-size: clamp(2rem, 4.4vw, 3.4rem);
  line-height: 1.1;
  margin: 0 auto var(--space-4);
  max-width: 22ch;
  letter-spacing: -0.02em;
  background: linear-gradient(135deg, var(--c-teal-deep), var(--c-indigo) 55%, var(--c-violet));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero__lede {
  max-width: 70ch;
  margin: 0 auto var(--space-5);
  font-size: clamp(1.05rem, 1.4vw, 1.2rem);
  color: var(--c-ink-soft);
}
.hero__cta {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-4);
  margin-top: var(--space-6);
  text-align: left;
}
.cta-card {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  padding: var(--space-5);
  background: var(--c-surface);
  border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  color: var(--c-ink);
  border-bottom-width: 1px;
  transition: transform 180ms ease, box-shadow 180ms ease, border-color 180ms ease;
}
.cta-card:hover,
.cta-card:focus-visible {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: rgba(14, 124, 123, 0.45);
  color: var(--c-ink);
}
.cta-card__icon {
  flex: 0 0 48px;
  width: 48px;
  height: 48px;
  border-radius: 14px;
  display: grid;
  place-items: center;
  color: #fff;
}
.cta-card__icon--teal   { background: linear-gradient(135deg, #0e7c7b, #76c7b8); }
.cta-card__icon--indigo { background: linear-gradient(135deg, #3949ab, #7e3ff2); }
.cta-card__icon--coral  { background: linear-gradient(135deg, #e26d5c, #f6c14a); }
.cta-card__icon svg {
  width: 26px;
  height: 26px;
}
.cta-card h3 {
  margin: 0 0 var(--space-1);
  font-size: 1.1rem;
}
.cta-card p {
  margin: 0;
  color: var(--c-ink-soft);
  font-size: 0.95rem;
}

/* Section description grid on home */
.section-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(290px, 1fr));
  gap: var(--space-5);
  margin: var(--space-7) 0;
}
.section-card {
  background: var(--c-surface);
  border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-md);
  padding: var(--space-5);
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  transition: transform 180ms ease, box-shadow 180ms ease;
}
.section-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}
.section-card h3 {
  margin: 0;
  font-size: 1.15rem;
}
.section-card h3 a {
  color: var(--c-teal-deep);
  border-bottom: 0;
}
.section-card h3 a:hover { color: var(--c-violet); }
.section-card p {
  margin: 0;
  color: var(--c-ink-soft);
  font-size: 0.97rem;
}
.section-card ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}
.section-card ul li a {
  display: inline-block;
  font-size: 0.85rem;
  padding: 0.25rem 0.6rem;
  background: rgba(57, 73, 171, 0.08);
  border-radius: 999px;
  color: var(--c-indigo);
  border-bottom: 0;
}
.section-card ul li a:hover {
  background: rgba(126, 63, 242, 0.14);
  color: var(--c-violet);
}

.home-section {
  margin-top: var(--space-8);
}
.home-section h2 {
  font-size: clamp(1.5rem, 2.4vw, 1.9rem);
  margin: 0 0 var(--space-4);
  letter-spacing: -0.01em;
}

/* ---------- Content page ---------- */

.content-shell {
  display: block;
}
.breadcrumb {
  font-size: 0.9rem;
  color: var(--c-muted);
  margin: 0 0 var(--space-4);
  word-break: break-word;
}
.breadcrumb ol {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  align-items: center;
}
.breadcrumb li + li::before {
  content: "›";
  margin-right: var(--space-2);
  color: var(--c-muted);
}
.breadcrumb a {
  color: var(--c-ink-soft);
  border-bottom: 0;
}
.breadcrumb a:hover { color: var(--c-teal); }
.breadcrumb [aria-current="page"] {
  color: var(--c-ink);
  font-weight: 500;
}

.article {
  background: var(--c-surface);
  border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-lg);
  padding: clamp(1.5rem, 3.5vw, 3rem) clamp(1.5rem, 4vw, 4rem);
  box-shadow: var(--shadow-sm);
}
/* Code blocks, tables, mermaid, related, and FAQ should span the full
   article width — only prose is constrained to the comfortable measure. */
.article .codeblock,
.article .table-wrap,
.article pre.mermaid,
.article .faq-list,
.article blockquote {
  max-width: none;
}

.article h1,
.article h2,
.article h3,
.article h4,
.article h5,
.article h6 {
  line-height: 1.25;
  letter-spacing: -0.01em;
  scroll-margin-top: calc(var(--header-h) + 24px);
}
/* Make sure any anchored element (not just headings) clears the sticky
   header when the browser jumps to its fragment. */
.article [id] {
  scroll-margin-top: calc(var(--header-h) + 24px);
}

.article h1 {
  font-size: clamp(1.9rem, 3vw, 2.6rem);
  margin: 0 0 var(--space-5);
  background: linear-gradient(135deg, var(--c-teal-deep), var(--c-indigo) 55%, var(--c-violet));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.article h2 {
  font-size: clamp(1.35rem, 2vw, 1.7rem);
  margin: var(--space-7) 0 var(--space-3);
  color: var(--c-teal-deep);
  border-bottom: 1px solid var(--c-border-soft);
  padding-bottom: var(--space-2);
}
.article h3 {
  font-size: 1.2rem;
  margin: var(--space-6) 0 var(--space-3);
  color: var(--c-indigo);
}
.article h4 {
  font-size: 1.05rem;
  margin: var(--space-5) 0 var(--space-2);
  color: var(--c-ink);
}

.article p {
  margin: 0 0 var(--space-4);
  color: var(--c-ink);
}
.article p, .article li {
  hyphens: auto;
}

/* Lists — styled markers, comfortable spacing */
.article ul,
.article ol {
  margin: var(--space-3) 0 var(--space-5);
  padding-left: 1.65rem;
}
.article ul { list-style: none; padding-left: 0; }
.article ul > li {
  position: relative;
  padding-left: 1.5rem;
}
.article ul > li::before {
  content: "";
  position: absolute;
  left: 0.25rem;
  top: 0.7em;
  width: 8px;
  height: 8px;
  border-radius: 3px;
  background: linear-gradient(135deg, var(--c-teal), var(--c-indigo));
  box-shadow: 0 1px 2px rgba(57, 73, 171, 0.25);
}
.article ul > li > ul > li::before {
  background: linear-gradient(135deg, var(--c-indigo), var(--c-violet));
  width: 6px;
  height: 6px;
  top: 0.78em;
}
.article ul > li > ul > li > ul > li::before {
  background: var(--c-coral);
  border-radius: 50%;
}

.article ol {
  list-style: none;
  counter-reset: ol-counter;
  padding-left: 0;
}
.article ol > li {
  position: relative;
  padding-left: 2.4rem;
  counter-increment: ol-counter;
}
.article ol > li::before {
  content: counter(ol-counter);
  position: absolute;
  left: 0;
  top: 0.15em;
  width: 1.75rem;
  height: 1.75rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, var(--c-teal-deep), var(--c-indigo));
  color: #fff;
  font-size: 0.78rem;
  font-weight: 700;
  border-radius: 999px;
  font-family: var(--font-mono);
  letter-spacing: -0.01em;
  box-shadow: var(--shadow-sm);
}

.article li {
  margin-bottom: var(--space-3);
  line-height: 1.6;
}
.article li > p { margin-bottom: var(--space-2); }
.article li > p:last-child { margin-bottom: 0; }
.article li > ul,
.article li > ol {
  margin: var(--space-2) 0 var(--space-2);
}
.article li > strong:first-child,
.article li > p:first-child > strong:first-child {
  color: var(--c-teal-deep);
}

/* Task lists override the prose bullet styling */
.article ul.contains-task-list { padding-left: 0; }
.article ul.contains-task-list > li { padding-left: 0; }
.article ul.contains-task-list > li::before { content: none; }

/* Heading anchor links */
.heading-anchor {
  color: inherit;
  border-bottom: 0;
}
.heading-anchor:hover {
  color: var(--c-violet);
}

/* Inline code */
.article :not(pre) > code {
  font-family: var(--font-mono);
  font-size: 0.92em;
  background: var(--c-code-inline-bg);
  color: var(--c-teal-deep);
  padding: 0.1em 0.4em;
  border-radius: 4px;
  border: 0;
}

/* Code blocks */
.codeblock {
  position: relative;
  margin: var(--space-5) 0;
  background: var(--c-code-bg);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: inset 0 1px 0 rgba(255,255,255,0.6), var(--shadow-sm);
}
.codeblock__bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.45rem 0.85rem;
  background: rgba(14, 124, 123, 0.07);
  border-bottom: 1px solid var(--c-border);
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--c-teal-deep);
  font-weight: 600;
}
.codeblock__copy {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  color: var(--c-ink-soft);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  padding: 0.3rem 0.7rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background 140ms ease, color 140ms ease, border-color 140ms ease;
}
.codeblock__copy:hover {
  background: var(--c-teal);
  color: #fff;
  border-color: var(--c-teal);
}
.codeblock__copy.is-copied {
  background: var(--c-mint);
  color: #033b3a;
  border-color: var(--c-mint);
}
.codeblock pre {
  margin: 0;
  padding: 1rem 1.1rem;
  overflow-x: auto;
  font-size: 0.92rem;
  line-height: 1.6;
  background: transparent;
  color: var(--c-ink);
  font-family: var(--font-mono);
  tab-size: 4;
  -moz-tab-size: 4;
}
.codeblock pre code {
  background: transparent;
  padding: 0;
  font-family: inherit;
  color: inherit;
}

/* Prism light theme — site palette */
.token.comment, .token.prolog, .token.doctype, .token.cdata { color: #7a8295; font-style: italic; }
.token.punctuation { color: #475066; }
.token.namespace { opacity: .7; }
.token.property, .token.tag, .token.boolean, .token.number,
.token.constant, .token.symbol, .token.deleted { color: #b3551c; }
.token.selector, .token.attr-name, .token.string, .token.char,
.token.builtin, .token.inserted { color: #0e7c7b; }
.token.operator, .token.entity, .token.url, .language-css .token.string,
.style .token.string { color: #3949ab; }
.token.atrule, .token.attr-value, .token.keyword { color: #7e3ff2; }
.token.function, .token.class-name { color: #b04372; }
.token.regex, .token.important, .token.variable { color: #c2410c; }
.token.important, .token.bold { font-weight: 700; }
.token.italic { font-style: italic; }

/* Mermaid container — replicate codeblock styling */
pre.mermaid {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-md);
  padding: var(--space-5);
  margin: var(--space-5) 0;
  font-family: var(--font-sans);
  overflow-x: auto;
  box-shadow: var(--shadow-sm);
}

/* ---------- Tables ---------- */
.article table,
.table-wrap > table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
}
.table-wrap {
  width: 100%;
  overflow-x: auto;
  margin: var(--space-5) 0;
  border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-md);
  background: var(--c-surface);
  -webkit-overflow-scrolling: touch;
}
.table-wrap > table {
  margin: 0;
}
.table-wrap th, .table-wrap td {
  padding: 0.7rem 0.9rem;
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--c-border-soft);
}
.table-wrap thead th {
  background: linear-gradient(180deg, rgba(14, 124, 123, 0.10), rgba(57, 73, 171, 0.08));
  color: var(--c-teal-deep);
  font-weight: 600;
  white-space: nowrap;
}
.table-wrap tbody tr:nth-child(odd) {
  background: rgba(14, 124, 123, 0.025);
}
.table-wrap tbody tr:hover {
  background: rgba(126, 63, 242, 0.06);
}

/* ---------- Block quotes ---------- */
.article blockquote {
  margin: var(--space-5) 0;
  padding: var(--space-4) var(--space-5);
  background: rgba(14, 124, 123, 0.06);
  border-left: 4px solid var(--c-teal);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  color: var(--c-ink-soft);
}
.article blockquote p:last-child { margin-bottom: 0; }

/* ---------- Task lists (interactive checkboxes) ---------- */
.article ul li.task-list-item {
  list-style: none;
  margin-left: -1.25rem;
  padding-left: 0;
  display: flex;
  align-items: flex-start;
  gap: 0.55rem;
}
.article ul li.task-list-item::marker { content: ""; }
.article ul li.task-list-item input[type="checkbox"] {
  margin-top: 0.35rem;
  width: 18px;
  height: 18px;
  accent-color: var(--c-teal);
  cursor: pointer;
}
.article ul li.task-list-item.is-checked {
  color: var(--c-muted);
  text-decoration: line-through;
}

/* ---------- FAQ accordion ---------- */
.faq-list { margin: var(--space-5) 0; display: flex; flex-direction: column; gap: var(--space-3); }
.faq-item {
  background: var(--c-surface);
  border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
}
.faq-item[open] {
  border-color: rgba(14, 124, 123, 0.5);
}
.faq-item summary {
  cursor: pointer;
  padding: var(--space-4) var(--space-5);
  font-weight: 600;
  color: var(--c-teal-deep);
  list-style: none;
  position: relative;
  padding-right: 2.4rem;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after {
  content: "+";
  position: absolute;
  right: 1.2rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.3rem;
  color: var(--c-violet);
  transition: transform 180ms ease;
}
.faq-item[open] summary::after {
  content: "−";
}
.faq-body {
  padding: 0 var(--space-5) var(--space-5);
  color: var(--c-ink-soft);
}

/* ---------- Related pages ---------- */
.related {
  margin-top: var(--space-7);
  padding: clamp(1.25rem, 2.5vw, 2rem);
  background: linear-gradient(180deg, var(--c-bg-soft) 0%, #f1ecde 100%);
  border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-lg);
  position: relative;
  overflow: hidden;
}
.related::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(14, 124, 123, 0.05), rgba(126, 63, 242, 0.04));
  pointer-events: none;
}
.related > * { position: relative; }
.related h2 {
  margin: 0 0 var(--space-5);
  font-size: 0.85rem;
  color: var(--c-teal-deep);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  display: flex;
  align-items: center;
  gap: var(--space-3);
}
.related h2::after {
  content: "";
  flex: 1;
  height: 1px;
  background: linear-gradient(90deg, var(--c-border) 0%, transparent 100%);
}
.related__group + .related__group {
  margin-top: var(--space-5);
  padding-top: var(--space-5);
  border-top: 1px dashed var(--c-border);
}
.related__group h3 {
  font-size: 0.74rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--c-muted);
  margin: 0 0 var(--space-3);
  font-weight: 600;
}
.related ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: var(--space-3);
  max-width: none;
}
.related ul > li { margin: 0; padding: 0; }
.related ul > li::before { content: none; }
.related li a {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: 0.7rem 0.95rem;
  background: var(--c-surface);
  border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-md);
  font-size: 0.95rem;
  color: var(--c-ink);
  border-bottom: 1px solid var(--c-border-soft);
  font-weight: 500;
  line-height: 1.35;
  box-shadow: var(--shadow-sm);
  transition: transform 160ms ease, box-shadow 160ms ease,
              border-color 160ms ease, color 160ms ease;
}
.related li a::before {
  content: "";
  width: 8px;
  height: 8px;
  flex: 0 0 8px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--c-teal), var(--c-indigo));
  box-shadow: 0 0 0 3px rgba(14, 124, 123, 0.12);
  transition: transform 160ms ease, background 160ms ease,
              box-shadow 160ms ease;
}
.related li a::after {
  content: "→";
  margin-left: auto;
  font-size: 1.05rem;
  color: var(--c-muted);
  transition: transform 160ms ease, color 160ms ease;
}
.related li a:hover,
.related li a:focus-visible {
  transform: translateY(-2px);
  border-color: rgba(126, 63, 242, 0.5);
  box-shadow: var(--shadow-md);
  color: var(--c-teal-deep);
}
.related li a:hover::before {
  background: linear-gradient(135deg, var(--c-violet), var(--c-coral));
  box-shadow: 0 0 0 4px rgba(126, 63, 242, 0.15);
}
.related li a:hover::after {
  color: var(--c-violet);
  transform: translateX(3px);
}

/* Parent section gets a single full-width row */
.related__group:first-of-type ul {
  grid-template-columns: 1fr;
}
.related__group:first-of-type li a {
  background: linear-gradient(135deg, rgba(14, 124, 123, 0.08), rgba(126, 63, 242, 0.06));
  border-color: rgba(14, 124, 123, 0.25);
}

/* ---------- Table of contents ---------- */
.article .toc {
  margin: var(--space-5) 0 var(--space-6);
  padding: var(--space-4) var(--space-5);
  background: linear-gradient(180deg, rgba(14, 124, 123, 0.05), rgba(126, 63, 242, 0.04));
  border: 1px solid var(--c-border-soft);
  border-left: 4px solid var(--c-teal);
  border-radius: var(--radius-md);
  max-width: none;
}
/* Scope under .article so we win specificity against `.article h2`. */
.article .toc .toc__title {
  margin: 0 0 var(--space-3);
  padding: 0;
  border: 0;
  background: none;
  font-size: 0.78rem;
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--c-teal-deep);
  -webkit-background-clip: initial;
  background-clip: initial;
  -webkit-text-fill-color: var(--c-teal-deep);
  display: flex;
  align-items: center;
  gap: var(--space-3);
}
.article .toc .toc__title::after {
  content: "";
  flex: 1;
  height: 1px;
  background: linear-gradient(90deg, var(--c-border) 0%, transparent 100%);
}
.toc__list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 0.35rem 1.25rem;
}
.toc__item {
  margin: 0;
  padding: 0;
  font-size: 0.94rem;
  line-height: 1.45;
}
.toc__item::before { content: none !important; }
.toc__item a {
  display: inline-flex;
  align-items: baseline;
  gap: 0.5rem;
  padding: 0.18rem 0;
  color: var(--c-ink-soft);
  border-bottom: 0;
  transition: color 140ms ease, transform 140ms ease;
}
.toc__item a:hover,
.toc__item a:focus-visible {
  color: var(--c-violet);
  transform: translateX(2px);
}
.toc__item--h3 {
  padding-left: 1.5rem;
  font-size: 0.88rem;
}
.toc__item--h3 > a::before {
  content: "↳";
  color: var(--c-muted);
}

/* ---------- Callouts (info / warning / key concept) ---------- */
.article .callout,
.article blockquote.callout {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  margin: var(--space-5) 0;
  padding: var(--space-4) var(--space-5);
  background: var(--c-bg-soft);
  border: 1px solid var(--c-border-soft);
  border-left: 4px solid var(--c-teal);
  border-radius: var(--radius-md);
  color: var(--c-ink);
}
.article .callout::before,
.article blockquote.callout::before {
  content: "i";
  flex: 0 0 28px;
  height: 28px;
  display: grid;
  place-items: center;
  background: var(--c-teal);
  color: #fff;
  font-weight: 700;
  font-family: var(--font-mono);
  border-radius: 50%;
  font-size: 0.85rem;
}
.article .callout--warning,
.article blockquote.callout--warning {
  border-left-color: var(--c-coral);
  background: rgba(226, 109, 92, 0.06);
}
.article .callout--warning::before,
.article blockquote.callout--warning::before {
  content: "!";
  background: var(--c-coral);
}
.article .callout--key,
.article blockquote.callout--key {
  border-left-color: var(--c-violet);
  background: rgba(126, 63, 242, 0.06);
}
.article .callout--key::before,
.article blockquote.callout--key::before {
  content: "★";
  background: var(--c-violet);
}
.article .callout > *,
.article blockquote.callout > * { margin: 0 0 var(--space-2); }
.article .callout > *:last-child,
.article blockquote.callout > *:last-child { margin-bottom: 0; }

/* ---------- KaTeX tweaks ---------- */
.katex-display {
  margin: var(--space-5) 0;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 0.4rem 0;
}
.katex { font-size: 1.02em; }

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

@media (max-width: 960px) {
  .site-footer__cols {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 720px) {
  :root { --header-h: 60px; }
  body { font-size: 16px; }
  .nav-toggle { display: inline-flex; align-items: center; }
  .site-nav {
    display: none;
    position: absolute;
    top: var(--header-h);
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    background: var(--c-surface);
    border-bottom: 1px solid var(--c-border-soft);
    padding: var(--space-3);
    gap: var(--space-1);
    box-shadow: var(--shadow-md);
  }
  .site-nav.is-open { display: flex; }
  .site-nav a {
    width: 100%;
    padding: 0.7rem 0.9rem;
  }
  .brand__text--full { display: none; }
  .brand__text--short { display: inline; }
  .site-footer__cols { grid-template-columns: 1fr; }
  .article { padding: 1rem 1rem; border-radius: var(--radius-md); }
}

@media (min-width: 1500px) {
  body { font-size: 18px; }
}