/* ============================================================
   Geostatistical Modeling — Colorful Daybreak palette
   Deep violet → playful yellow & orange. Morning optimism.
   ============================================================ */

:root {
  /* Brand */
  --violet-900: #2d1b69;
  --violet-700: #5b3fa1;
  --violet-500: #7c5ce6;
  --violet-400: #9c81f0;
  --violet-200: #d8ccfa;
  --violet-100: #ebe4ff;
  --violet-50:  #f4f0ff;

  --orange-600: #f06a1f;
  --orange-500: #ff8a3d;
  --orange-400: #ffa05c;

  --yellow-500: #ffc726;
  --yellow-400: #ffd24a;
  --yellow-200: #fff3c4;
  --yellow-100: #fff8df;

  /* Ink + surface */
  --ink-900: #1a1430;
  --ink-700: #2e2750;
  --ink-600: #4a4365;
  --ink-500: #6b6489;
  --ink-300: #aaa3c2;

  --surface: #ffffff;
  --surface-soft: #fbf8ff;
  --surface-tint: #f6f1ff;
  --code-bg: #f6f1ff;
  --code-inline-bg: #ece2ff;

  --border: rgba(124, 92, 230, 0.18);
  --border-strong: rgba(124, 92, 230, 0.35);

  --shadow-sm: 0 1px 2px rgba(45, 27, 105, 0.06), 0 2px 6px rgba(45, 27, 105, 0.04);
  --shadow-md: 0 4px 14px rgba(45, 27, 105, 0.08), 0 10px 24px rgba(45, 27, 105, 0.06);
  --shadow-lg: 0 12px 40px rgba(45, 27, 105, 0.18);
  --shadow-glow: 0 8px 30px rgba(124, 92, 230, 0.25);

  --grad-hero: linear-gradient(135deg, #2d1b69 0%, #5b3fa1 35%, #7c5ce6 55%, #ff8a3d 88%, #ffd24a 100%);
  --grad-accent: linear-gradient(90deg, var(--violet-500), var(--orange-500), var(--yellow-400));
  --grad-card: linear-gradient(155deg, rgba(124,92,230,0.06), rgba(255,138,61,0.04) 70%, rgba(255,210,74,0.06));

  /* Layout */
  --container-narrow: 72ch;
  --container-wide:   min(1400px, 92vw);
  --container-full:   min(1600px, 96vw);
  --container-prose:  min(1200px, 92vw);

  --header-h: 64px;
  --radius-sm: 6px;
  --radius:    12px;
  --radius-lg: 18px;
  --radius-xl: 28px;

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

  --t-fast: 140ms cubic-bezier(.4,0,.2,1);
  --t-base: 220ms cubic-bezier(.4,0,.2,1);
  --t-slow: 360ms cubic-bezier(.4,0,.2,1);
}

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

/* Reset / base */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: clamp(1rem, 0.96rem + 0.2vw, 1.0625rem);
  line-height: 1.65;
  color: var(--ink-900);
  background:
    radial-gradient(1200px 600px at 8% -10%, rgba(124,92,230,0.10), transparent 60%),
    radial-gradient(900px 500px at 95% 0%, rgba(255,138,61,0.07), transparent 55%),
    var(--violet-50);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

main { flex: 1; }

img, svg { display: block; max-width: 100%; height: auto; }
button { font: inherit; cursor: pointer; }

a {
  color: var(--violet-700);
  text-decoration: none;
  background-image: linear-gradient(90deg, var(--violet-500), var(--orange-500));
  background-repeat: no-repeat;
  background-size: 0% 2px;
  background-position: 0 100%;
  transition: color var(--t-base), background-size var(--t-base);
}
a:hover { color: var(--violet-900); background-size: 100% 2px; }
a:focus-visible { outline: 3px solid var(--violet-400); outline-offset: 2px; border-radius: 3px; }

h1, h2, h3, h4, h5 {
  font-family: var(--font-display);
  color: var(--ink-900);
  line-height: 1.2;
  margin: 0 0 0.6em;
  letter-spacing: -0.01em;
}
h1 { font-size: clamp(2rem, 1.5rem + 2.2vw, 3.25rem); font-weight: 800; }
h2 { font-size: clamp(1.5rem, 1.15rem + 1.4vw, 2.1rem); font-weight: 700; margin-top: 1.8em; }
h3 { font-size: clamp(1.2rem, 1.05rem + 0.7vw, 1.5rem); font-weight: 700; margin-top: 1.4em; }
h4 { font-size: 1.125rem; font-weight: 700; margin-top: 1.1em; }

p { margin: 0 0 1em; }

::selection { background: var(--violet-200); color: var(--ink-900); }

/* Container utilities */
.container { width: var(--container-wide); margin: 0 auto; }
.container-full { width: var(--container-full); margin: 0 auto; }
.container-prose { width: var(--container-prose); margin: 0 auto; }

/* ============================================================
   Header / Nav
   ============================================================ */

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  background: rgba(255, 255, 255, 0.82);
  border-bottom: 1px solid var(--border);
}

.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  gap: 1rem;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.7rem;
  background: none;
  font-weight: 700;
  color: var(--ink-900);
}
.brand:hover { background: none; color: var(--violet-700); }
.brand__mark {
  width: 36px;
  height: 36px;
  display: grid;
  place-items: center;
  border-radius: 10px;
  background: var(--grad-accent);
  box-shadow: var(--shadow-glow);
}
.brand__mark svg { width: 22px; height: 22px; color: white; }
.brand__name {
  font-size: 1.02rem;
  line-height: 1.1;
  letter-spacing: -0.01em;
  display: none;
}
@media (min-width: 640px) {
  .brand__name { display: inline-block; }
}
.brand__name strong { display: block; font-weight: 800; }
.brand__name small { color: var(--ink-500); font-weight: 500; font-size: 0.78rem; }

.nav {
  display: none;
  gap: 0.25rem;
  align-items: center;
}
@media (min-width: 1024px) {
  .nav { display: inline-flex; }
}

.nav__link {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.5rem 0.9rem;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 0.94rem;
  color: var(--ink-700);
  background: none;
  transition: color var(--t-base), background var(--t-base), transform var(--t-base);
}
.nav__link:hover {
  color: var(--violet-900);
  background: var(--violet-100);
  background-image: none;
}
.nav__link[aria-current="page"] {
  color: var(--violet-900);
  background: var(--violet-100);
}
.nav__link[aria-current="page"]::after {
  content: "";
  position: absolute;
  bottom: -6px;
  left: 12%;
  right: 12%;
  height: 3px;
  border-radius: 2px;
  background: var(--grad-accent);
}
.nav__link { position: relative; }
.nav__icon { width: 18px; height: 18px; flex-shrink: 0; }

.nav-toggle {
  display: inline-grid;
  place-items: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  background: var(--violet-100);
  color: var(--violet-900);
  border: 1px solid var(--border);
}
.nav-toggle:hover { background: var(--violet-200); }
@media (min-width: 1024px) { .nav-toggle { display: none; } }

.nav-drawer {
  display: none;
  position: absolute;
  top: var(--header-h);
  left: 0;
  right: 0;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-md);
  padding: 0.5rem 0;
}
.nav-drawer[data-open="true"] { display: block; }
.nav-drawer .nav__link {
  display: flex;
  width: 100%;
  border-radius: 0;
  padding: 0.85rem 1.2rem;
}
@media (min-width: 1024px) { .nav-drawer { display: none !important; } }

/* ============================================================
   Hero / Frontpage
   ============================================================ */

.hero {
  position: relative;
  margin: 2rem auto 3rem;
  border-radius: var(--radius-xl);
  overflow: hidden;
  color: white;
  background: var(--grad-hero);
  box-shadow: var(--shadow-lg);
}
.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(600px 300px at 12% 8%, rgba(255,255,255,0.22), transparent 60%),
    radial-gradient(700px 350px at 85% 90%, rgba(255,210,74,0.30), transparent 60%);
  pointer-events: none;
}
.hero__inner {
  position: relative;
  padding: clamp(2rem, 4vw, 4rem) clamp(1.25rem, 3vw, 3rem);
  display: grid;
  gap: 1.5rem;
  max-width: 1100px;
}
.hero__eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.3rem 0.75rem;
  border-radius: 999px;
  background: rgba(255,255,255,0.18);
  border: 1px solid rgba(255,255,255,0.35);
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  width: max-content;
}
.hero h1 {
  color: white;
  font-size: clamp(2.1rem, 1.4rem + 3vw, 3.6rem);
  margin: 0;
  line-height: 1.08;
}
.hero h1 .accent {
  background: linear-gradient(90deg, #ffd24a, #ff8a3d);
  background-clip: text;
  -webkit-background-clip: text;
  color: transparent;
}
.hero__lede {
  font-size: clamp(1.05rem, 0.95rem + 0.4vw, 1.25rem);
  max-width: 70ch;
  color: rgba(255,255,255,0.92);
}
.hero__cta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem;
  margin-top: 0.5rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.85rem 1.2rem;
  border-radius: 999px;
  font-weight: 700;
  font-size: 0.98rem;
  background: white;
  color: var(--violet-900);
  border: 1px solid transparent;
  box-shadow: var(--shadow-md);
  transition: transform var(--t-base), box-shadow var(--t-base), background var(--t-base);
  background-image: none;
}
.btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  background: white;
  color: var(--violet-900);
}
.btn--ghost {
  background: rgba(255,255,255,0.12);
  color: white;
  border-color: rgba(255,255,255,0.4);
  backdrop-filter: blur(4px);
}
.btn--ghost:hover { background: rgba(255,255,255,0.22); color: white; }
.btn__icon {
  width: 28px; height: 28px;
  display: grid; place-items: center;
  border-radius: 50%;
  background: var(--grad-accent);
  color: white;
  flex-shrink: 0;
}
.btn__icon svg { width: 16px; height: 16px; }

/* Sections */
.section { margin: 3.5rem auto; }
.section__head { margin-bottom: 1.5rem; max-width: 70ch; }
.section__head h2 {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
}
.section__head h2::before {
  content: "";
  width: 8px; height: 28px;
  border-radius: 4px;
  background: var(--grad-accent);
}
.section__head p { color: var(--ink-600); }

/* Card grids */
.cards {
  display: grid;
  gap: 1.25rem;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}
.card {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  padding: 1.4rem 1.4rem 1.3rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  transition: transform var(--t-base), box-shadow var(--t-base), border-color var(--t-base);
  overflow: hidden;
  background-image: none;
}
.card::before {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--grad-card);
  opacity: 0;
  transition: opacity var(--t-base);
  pointer-events: none;
}
.card:hover {
  transform: translateY(-4px);
  border-color: var(--border-strong);
  box-shadow: var(--shadow-md);
  color: inherit;
}
.card:hover::before { opacity: 1; }
.card__icon {
  width: 44px; height: 44px;
  border-radius: 12px;
  display: grid; place-items: center;
  background: var(--grad-accent);
  color: white;
  box-shadow: var(--shadow-glow);
  position: relative;
}
.card__icon svg { width: 22px; height: 22px; }
.card--violet .card__icon { background: linear-gradient(135deg, var(--violet-500), var(--violet-900)); }
.card--orange .card__icon { background: linear-gradient(135deg, var(--orange-500), var(--orange-600)); }
.card--yellow .card__icon { background: linear-gradient(135deg, var(--yellow-500), var(--orange-500)); }
.card h3 {
  margin: 0;
  font-size: 1.18rem;
  position: relative;
}
.card p {
  color: var(--ink-600);
  margin: 0;
  position: relative;
  flex: 1;
}
.card__link {
  position: relative;
  margin-top: 0.4rem;
  font-weight: 700;
  color: var(--violet-700);
  background: none;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
}
.card__link::after {
  content: "→";
  transition: transform var(--t-base);
}
.card:hover .card__link { color: var(--violet-900); }
.card:hover .card__link::after { transform: translateX(4px); }

.subpillar-group { margin-top: 2rem; }
.subpillar-group h3 {
  font-size: 1rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-500);
  margin-bottom: 0.75rem;
}
.chip-grid {
  display: grid;
  gap: 0.6rem;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
}
.chip {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  padding: 0.75rem 1rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--ink-900);
  font-weight: 600;
  background-image: none;
  transition: transform var(--t-base), border-color var(--t-base), box-shadow var(--t-base);
}
.chip:hover {
  transform: translateY(-2px);
  border-color: var(--border-strong);
  box-shadow: var(--shadow-sm);
  color: var(--violet-900);
}
.chip__dot {
  width: 10px; height: 10px; border-radius: 50%;
  background: var(--grad-accent);
  flex-shrink: 0;
}

.article-list {
  display: grid;
  gap: 0.8rem;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
}
.article-item {
  display: block;
  padding: 1rem 1.15rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background-image: none;
  transition: border-color var(--t-base), transform var(--t-base);
}
.article-item:hover {
  border-color: var(--border-strong);
  transform: translateY(-2px);
  color: var(--violet-900);
}
.article-item__breadcrumb {
  font-size: 0.78rem;
  color: var(--ink-500);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.3rem;
}
.article-item__title { font-weight: 700; }

/* ============================================================
   Content pages — prose
   ============================================================ */

.page {
  padding: 1.25rem 0 4rem;
}
.breadcrumbs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  font-size: 0.85rem;
  color: var(--ink-500);
  margin: 1rem 0 1.4rem;
  list-style: none;
  padding: 0;
}
.breadcrumbs li { display: inline-flex; align-items: center; gap: 0.35rem; }
.breadcrumbs li + li::before {
  content: "›";
  color: var(--ink-300);
  margin: 0 0.1rem;
}
.breadcrumbs a {
  color: var(--ink-600);
  background: none;
}
.breadcrumbs a:hover { color: var(--violet-700); background: none; }
.breadcrumbs li[aria-current="page"] { color: var(--violet-700); font-weight: 600; }

.prose { width: 100%; max-width: 100%; margin: 0; }
.prose > h1:first-of-type,
.page > h1:first-of-type {
  background: linear-gradient(90deg, var(--violet-700), var(--orange-500) 80%, var(--yellow-500));
  background-clip: text;
  -webkit-background-clip: text;
  color: transparent;
  margin-top: 0.2em;
}

.prose h2, .prose h3, .prose h4 {
  scroll-margin-top: calc(var(--header-h) + 1.2rem);
}
.prose h2 { color: var(--violet-900); }
.prose h2::before {
  content: "";
  display: inline-block;
  width: 6px; height: 22px;
  border-radius: 3px;
  background: var(--grad-accent);
  margin-right: 0.6rem;
  vertical-align: -3px;
}
.prose h3 { color: var(--violet-700); }
.prose h4 { color: var(--ink-700); }

.prose ul, .prose ol { padding-left: 1.4rem; }
.prose li { margin-bottom: 0.35rem; }
.prose li::marker { color: var(--violet-500); }

.prose blockquote {
  margin: 1.4rem 0;
  padding: 0.8rem 1.2rem;
  background: var(--violet-50);
  border-left: 4px solid var(--violet-500);
  border-radius: var(--radius-sm);
  color: var(--ink-700);
}

.prose hr {
  border: none;
  height: 2px;
  background: var(--grad-accent);
  opacity: 0.5;
  margin: 2rem 0;
  border-radius: 2px;
}

/* Inline code */
.prose :not(pre) > code,
.prose p code,
.prose li code,
.prose td code,
.prose th code,
.prose h2 code,
.prose h3 code,
.prose h4 code {
  background: var(--code-inline-bg);
  color: var(--violet-900);
  padding: 0.1em 0.4em;
  border-radius: 5px;
  font-size: 0.9em;
  border: none;
  font-family: var(--font-mono);
}

/* Task list checkboxes (markdown-it-task-lists) */
.prose ul.contains-task-list { list-style: none; padding-left: 0.5rem; }
.prose .task-list-item { list-style: none; padding-left: 0; display: flex; gap: 0.55rem; align-items: flex-start; }
.prose .task-list-item input.task-list-item-checkbox {
  appearance: none;
  -webkit-appearance: none;
  width: 18px; height: 18px;
  border: 2px solid var(--violet-500);
  border-radius: 4px;
  margin-top: 0.32em;
  cursor: pointer;
  background: var(--surface);
  transition: background var(--t-fast), border-color var(--t-fast);
  flex-shrink: 0;
  position: relative;
}
.prose .task-list-item input.task-list-item-checkbox:checked {
  background: var(--grad-accent);
  border-color: var(--violet-700);
}
.prose .task-list-item input.task-list-item-checkbox:checked::after {
  content: "";
  position: absolute;
  left: 4px; top: 1px;
  width: 5px; height: 9px;
  border: solid white;
  border-width: 0 2.5px 2.5px 0;
  transform: rotate(45deg);
}
.prose .task-list-item.task-done { color: var(--ink-500); }
.prose .task-list-item.task-done > * { text-decoration: line-through; text-decoration-color: var(--ink-300); }
/* Remove default disc marker since list-style is none */
.prose .contains-task-list .contains-task-list { padding-left: 1.4rem; }

/* Tables */
.table-scroll {
  overflow-x: auto;
  margin: 1.4rem 0;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--surface);
  box-shadow: var(--shadow-sm);
}
.prose table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
}
.prose thead th {
  background: var(--violet-50);
  color: var(--violet-900);
  font-weight: 700;
  text-align: left;
  padding: 0.7rem 1rem;
  border-bottom: 1px solid var(--border);
}
.prose tbody td {
  padding: 0.65rem 1rem;
  border-bottom: 1px solid var(--border);
  vertical-align: top;
}
.prose tbody tr:last-child td { border-bottom: none; }
.prose tbody tr:hover { background: var(--violet-50); }

/* Codeblocks */
.codeblock {
  margin: 1.4rem 0;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--code-bg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}
.codeblock__bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.45rem 0.85rem;
  background: linear-gradient(90deg, rgba(124,92,230,0.10), rgba(255,138,61,0.06));
  border-bottom: 1px solid var(--border);
  font-size: 0.78rem;
}
.codeblock__lang {
  color: var(--violet-700);
  font-family: var(--font-mono);
  font-weight: 700;
  text-transform: lowercase;
  letter-spacing: 0.04em;
}
.codeblock__copy {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.3rem 0.65rem;
  border-radius: var(--radius-sm);
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--violet-700);
  font-weight: 600;
  font-size: 0.78rem;
  transition: background var(--t-fast), color var(--t-fast), transform var(--t-fast);
}
.codeblock__copy:hover { background: var(--violet-100); color: var(--violet-900); }
.codeblock__copy.is-copied { background: var(--grad-accent); color: white; border-color: transparent; }
.codeblock pre {
  margin: 0;
  padding: 1rem 1.15rem;
  overflow-x: auto;
  background: var(--code-bg);
  color: var(--ink-900);
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.55;
}
.codeblock pre code { background: none; padding: 0; border: 0; color: inherit; font-size: inherit; }

/* highlight.js — Daybreak theme overrides */
.hljs { background: transparent; color: var(--ink-900); }
.hljs-comment, .hljs-quote { color: var(--ink-500); font-style: italic; }
.hljs-keyword, .hljs-selector-tag, .hljs-built_in, .hljs-name { color: var(--violet-700); font-weight: 600; }
.hljs-string, .hljs-attr, .hljs-symbol, .hljs-bullet { color: var(--orange-600); }
.hljs-number, .hljs-literal { color: var(--orange-500); }
.hljs-title, .hljs-section, .hljs-type, .hljs-class .hljs-title { color: var(--violet-900); font-weight: 700; }
.hljs-function .hljs-title { color: var(--violet-700); }
.hljs-params { color: var(--ink-700); }
.hljs-meta { color: var(--ink-500); }
.hljs-tag { color: var(--violet-700); }
.hljs-variable, .hljs-template-variable, .hljs-attribute { color: var(--violet-700); }
.hljs-regexp, .hljs-link { color: var(--orange-600); }
.hljs-deletion { color: #c43c3c; background: rgba(255, 0, 0, 0.06); }
.hljs-addition { color: #2e7d3a; background: rgba(0, 255, 0, 0.06); }

/* KaTeX */
.katex-display {
  overflow-x: auto;
  overflow-y: hidden;
  padding: 0.5rem 0;
}
.katex { color: var(--ink-900); }

/* FAQ accordion */
.faq { display: grid; gap: 0.6rem; margin: 1rem 0 2rem; }
.faq-item {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: border-color var(--t-base);
}
.faq-item[open] { border-color: var(--border-strong); }
.faq-item summary {
  list-style: none;
  padding: 1rem 1.2rem;
  font-weight: 700;
  color: var(--violet-900);
  cursor: pointer;
  position: relative;
  padding-right: 3rem;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after {
  content: "+";
  position: absolute;
  right: 1.2rem;
  top: 50%;
  transform: translateY(-50%);
  width: 26px; height: 26px;
  border-radius: 50%;
  background: var(--violet-100);
  color: var(--violet-700);
  display: grid; place-items: center;
  font-weight: 700;
  font-size: 1.1rem;
  transition: transform var(--t-base), background var(--t-base);
}
.faq-item[open] summary::after {
  content: "−";
  background: var(--grad-accent);
  color: white;
  transform: translateY(-50%) rotate(180deg);
}
.faq-answer { padding: 0 1.2rem 1.1rem; color: var(--ink-700); }

/* Related / sibling list */
.related {
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
}
.related h2 {
  font-size: 1.15rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-500);
  margin-top: 0;
}

/* ============================================================
   Footer
   ============================================================ */

.site-footer {
  margin-top: 4rem;
  background: linear-gradient(180deg, transparent, var(--violet-50) 30%);
  border-top: 1px solid var(--border);
}
.site-footer__inner {
  padding: 2.5rem 0 1.5rem;
  display: grid;
  gap: 2rem;
  grid-template-columns: 1fr;
}
@media (min-width: 768px) {
  .site-footer__inner { grid-template-columns: 1.2fr 2fr; }
}
.site-footer__brand p { color: var(--ink-600); max-width: 40ch; }
.footer-grid {
  display: grid;
  gap: 1.5rem;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
}
.footer-grid h4 {
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-500);
  margin: 0 0 0.7rem;
}
.footer-grid ul { list-style: none; padding: 0; margin: 0; display: grid; gap: 0.4rem; }
.footer-grid a {
  background: none;
  color: var(--ink-700);
  font-size: 0.93rem;
}
.footer-grid a:hover { color: var(--violet-700); background: none; }
.site-footer__bottom {
  padding: 1rem 0 1.5rem;
  border-top: 1px solid var(--border);
  font-size: 0.85rem;
  color: var(--ink-500);
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  justify-content: space-between;
}

/* External link marker */
a.external::after {
  content: " ↗";
  font-size: 0.85em;
  color: var(--violet-500);
}

/* Header anchor link — a "#" placed after the heading text, visible on hover */
.prose h2 .header-anchor,
.prose h3 .header-anchor,
.prose h4 .header-anchor {
  display: inline-block;
  margin-left: 0.5rem;
  color: var(--violet-300);
  background: none;
  font-weight: 500;
  text-decoration: none;
  opacity: 0;
  transition: opacity var(--t-fast), color var(--t-fast);
  vertical-align: baseline;
}
.prose h2:hover .header-anchor,
.prose h3:hover .header-anchor,
.prose h4:hover .header-anchor { opacity: 1; }
.prose .header-anchor:hover { color: var(--violet-700); background: none; }

/* Mermaid */
.mermaid {
  margin: 1.4rem 0;
  padding: 1rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-align: center;
  overflow-x: auto;
}