/* =============================================================
   Spatial Lakehouse Architectures — design system
   Light, professional palette inspired by water + terrain + sun.
   ============================================================= */

:root {
  /* Palette */
  --c-bg: #f6f3ec;            /* parchment */
  --c-bg-soft: #fbf9f3;
  --c-surface: #ffffff;
  --c-surface-tint: #f0ece1;
  --c-ink: #1d2a33;
  --c-ink-soft: #4a5a66;
  --c-muted: #6f8290;
  --c-line: #dcd6c5;

  --c-primary: #0e6e7d;       /* deep teal — water/lakehouse */
  --c-primary-soft: #3fb8c4;
  --c-primary-tint: #d8eff2;
  --c-accent: #c87a1f;        /* amber sun */
  --c-accent-soft: #f1c560;
  --c-leaf: #3f8c5e;          /* terrain green */
  --c-leaf-soft: #7ec48b;
  --c-danger: #b94a4a;

  --pillar-color: var(--c-primary);

  /* Type scale (fluid) */
  --fs-h1: clamp(2.1rem, 1.4rem + 2.6vw, 3.4rem);
  --fs-h2: clamp(1.55rem, 1.15rem + 1.4vw, 2.15rem);
  --fs-h3: clamp(1.2rem, 1rem + 0.7vw, 1.55rem);
  --fs-h4: 1.1rem;
  --fs-body: clamp(1rem, 0.96rem + 0.15vw, 1.08rem);
  --fs-small: 0.875rem;

  /* Spacing */
  --sp-1: 0.25rem;
  --sp-2: 0.5rem;
  --sp-3: 0.75rem;
  --sp-4: 1rem;
  --sp-5: 1.5rem;
  --sp-6: 2rem;
  --sp-7: 3rem;
  --sp-8: 4rem;
  --sp-9: 6rem;

  /* Radii / shadows */
  --rad-1: 6px;
  --rad-2: 10px;
  --rad-3: 16px;
  --rad-4: 22px;
  --shadow-1: 0 1px 2px rgba(20, 40, 50, 0.05), 0 1px 1px rgba(20, 40, 50, 0.04);
  --shadow-2: 0 8px 24px rgba(20, 40, 50, 0.08), 0 2px 6px rgba(20, 40, 50, 0.05);
  --shadow-3: 0 18px 50px rgba(20, 40, 50, 0.12);

  /* Layout */
  --container: 1400px;
  --container-text: min(72ch, 100%);
  --header-h: 4rem;

  /* Fonts */
  --ff-sans: "Inter", "Segoe UI", system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
  --ff-mono: "JetBrains Mono", "Fira Code", "SF Mono", "Menlo", "Monaco", "Consolas", monospace;
}

@media (min-width: 1600px) {
  :root { --header-h: 4.5rem; --container: 1560px; }
}
@media (min-width: 1900px) {
  :root { --container: 1720px; }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
html, body { margin: 0; padding: 0; }

.icon {
  width: 1em;
  height: 1em;
  flex: none;
  display: inline-block;
  vertical-align: -0.15em;
  fill: currentColor;
}
svg.logo-mark { display: block; }

body {
  font-family: var(--ff-sans);
  font-size: var(--fs-body);
  line-height: 1.65;
  color: var(--c-ink);
  background: var(--c-bg);
  background-image:
    radial-gradient(1100px 600px at 85% -10%, rgba(63, 184, 196, 0.18), transparent 60%),
    radial-gradient(800px 500px at -10% 0%, rgba(241, 197, 96, 0.18), transparent 55%);
  background-attachment: fixed;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

.site-main {
  flex: 1 0 auto;
  padding-top: var(--sp-4);
  padding-bottom: var(--sp-8);
}

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

/* Skip link */
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--c-ink);
  color: white;
  padding: var(--sp-2) var(--sp-4);
  z-index: 1000;
}
.skip-link:focus { left: 0; }

/* ----------------------- Header ----------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  backdrop-filter: saturate(160%) blur(14px);
  -webkit-backdrop-filter: saturate(160%) blur(14px);
  background: rgba(255, 255, 255, 0.78);
  border-bottom: 1px solid var(--c-line);
}
.site-header__inner {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-4);
}
.site-header__brand {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-3);
  text-decoration: none;
  color: var(--c-ink);
}
.site-header__brand .logo-mark { width: 36px; height: 36px; transition: transform 0.25s ease; }
.site-header__brand:hover .logo-mark { transform: rotate(-6deg) scale(1.05); }
.site-header__title {
  display: flex;
  flex-direction: column;
  line-height: 1;
}
.site-header__title-main {
  font-weight: 700;
  font-size: 1.02rem;
  color: var(--c-primary);
  letter-spacing: 0.01em;
}
.site-header__title-sub {
  font-size: 0.78rem;
  color: var(--c-ink-soft);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-top: 2px;
}

.site-nav__list {
  display: flex;
  gap: var(--sp-2);
  margin: 0;
  padding: 0;
  list-style: none;
}
.site-nav__link {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.5rem 0.85rem;
  border-radius: var(--rad-2);
  font-weight: 500;
  font-size: 0.95rem;
  color: var(--c-ink-soft);
  text-decoration: none;
  transition: background 0.15s ease, color 0.15s ease, transform 0.15s ease;
  --pillar-color: var(--c-primary);
}
.site-nav__link:hover { color: var(--c-ink); background: var(--c-surface-tint); }
.site-nav__link.is-active {
  color: var(--pillar-color);
  background: color-mix(in srgb, var(--pillar-color) 12%, transparent);
  box-shadow: inset 0 -2px 0 var(--pillar-color);
}
.site-nav__link .icon { width: 1.05rem; height: 1.05rem; flex: none; }

/* Mobile nav */
.nav-toggle {
  display: none;
  border: 0;
  background: transparent;
  padding: 0.5rem;
  cursor: pointer;
  color: var(--c-ink);
}
.nav-toggle .icon { width: 1.5rem; height: 1.5rem; }
.nav-toggle .icon + .icon { display: none; }
.nav-toggle[aria-expanded="true"] .icon { display: none; }
.nav-toggle[aria-expanded="true"] .icon + .icon { display: inline-block; }

@media (max-width: 960px) {
  .nav-toggle { display: inline-flex; align-items: center; }
  .site-nav {
    position: absolute;
    top: var(--header-h);
    left: 0;
    right: 0;
    background: rgba(255,255,255,0.97);
    backdrop-filter: blur(14px);
    border-bottom: 1px solid var(--c-line);
    box-shadow: var(--shadow-2);
    transform: translateY(-110%);
    transition: transform 0.25s ease;
  }
  .site-nav.is-open { transform: translateY(0); }
  .site-nav__list { flex-direction: column; padding: var(--sp-3); gap: 0; }
  .site-nav__link { width: 100%; padding: 0.8rem 0.9rem; }
  .site-nav__link.is-active { box-shadow: inset 3px 0 0 var(--pillar-color); }
}

/* ----------------------- Hero ----------------------- */
.hero { padding-top: var(--sp-7); padding-bottom: var(--sp-7); }
.hero__inner { display: flex; flex-direction: column; align-items: center; text-align: center; gap: var(--sp-5); }
.hero__logo { width: clamp(140px, 22vw, 240px); }
.hero__logo .logo-mark { width: 100%; height: auto; filter: drop-shadow(0 14px 30px rgba(14, 110, 125, 0.25)); transition: transform 0.4s ease; }
.hero__logo:hover .logo-mark { transform: translateY(-4px); }
.hero__title { margin: 0; font-size: var(--fs-h1); line-height: 1.05; font-weight: 800; letter-spacing: -0.02em; }
.hero__title-line { display: block; }
.hero__title-accent {
  background: linear-gradient(90deg, var(--c-primary), var(--c-leaf) 60%, var(--c-accent));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero__tagline {
  margin: 0;
  font-size: clamp(1.05rem, 0.95rem + 0.5vw, 1.3rem);
  color: var(--c-ink-soft);
  max-width: 70ch;
}
.hero__ctas { display: flex; flex-wrap: wrap; gap: var(--sp-4); justify-content: center; margin-top: var(--sp-2); }

.cta-button {
  --pillar-color: var(--c-primary);
  display: inline-flex;
  align-items: center;
  gap: 0.85rem;
  padding: 0.95rem 1.35rem;
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: var(--rad-3);
  color: var(--c-ink);
  text-decoration: none;
  box-shadow: var(--shadow-1);
  transition: transform 0.18s ease, box-shadow 0.18s ease, border-color 0.18s ease;
  text-align: left;
}
.cta-button:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-2);
  border-color: color-mix(in srgb, var(--pillar-color) 60%, var(--c-line));
}
.cta-button__icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.4rem;
  height: 2.4rem;
  border-radius: 50%;
  background: color-mix(in srgb, var(--pillar-color) 14%, white);
  color: var(--pillar-color);
}
.cta-button__icon .icon { width: 1.35rem; height: 1.35rem; }
.cta-button__text { display: flex; flex-direction: column; line-height: 1.1; }
.cta-button__label { font-weight: 600; }
.cta-button__hint {
  font-size: 0.8rem;
  color: var(--c-muted);
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  margin-top: 0.25rem;
}
.cta-button__hint .icon { width: 0.9rem; height: 0.9rem; }

/* ----------------------- Sections ----------------------- */
.section-title {
  font-size: var(--fs-h2);
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 0 0 var(--sp-5);
  position: relative;
  padding-left: 0.85rem;
}
.section-title::before {
  content: "";
  position: absolute;
  left: 0; top: 0.45em; bottom: 0.45em;
  width: 4px;
  border-radius: 3px;
  background: linear-gradient(180deg, var(--c-primary), var(--c-leaf));
}

.intro { padding-block: var(--sp-7); }
.intro__copy { max-width: 100%; }
.intro__copy p { margin: 0 0 var(--sp-4); color: var(--c-ink-soft); }
@media (min-width: 1200px) {
  .intro__copy { columns: 2; column-gap: var(--sp-7); }
  .intro__copy p { break-inside: avoid; }
}

/* Pillar cards (home) */
.pillars { padding-block: var(--sp-7); }
.pillars__grid {
  display: grid;
  gap: var(--sp-5);
  grid-template-columns: 1fr;
}
@media (min-width: 900px) { .pillars__grid { grid-template-columns: repeat(3, 1fr); } }

.pillar-card {
  --pillar-color: var(--c-primary);
  background: var(--c-surface);
  border-radius: var(--rad-3);
  padding: var(--sp-5);
  border: 1px solid var(--c-line);
  box-shadow: var(--shadow-1);
  display: flex;
  flex-direction: column;
  gap: var(--sp-3);
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
  position: relative;
  overflow: hidden;
}
.pillar-card::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 4px;
  background: linear-gradient(90deg, var(--pillar-color), color-mix(in srgb, var(--pillar-color) 30%, white));
}
.pillar-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-2); border-color: color-mix(in srgb, var(--pillar-color) 50%, var(--c-line)); }
.pillar-card__header { display: flex; align-items: center; gap: 0.75rem; }
.pillar-card__icon {
  width: 2.6rem; height: 2.6rem;
  border-radius: 50%;
  display: inline-flex; align-items: center; justify-content: center;
  background: color-mix(in srgb, var(--pillar-color) 14%, white);
  color: var(--pillar-color);
}
.pillar-card__icon .icon { width: 1.5rem; height: 1.5rem; }
.pillar-card__title { margin: 0; font-size: var(--fs-h3); }
.pillar-card__title a { color: var(--c-ink); text-decoration: none; }
.pillar-card__title a:hover { color: var(--pillar-color); }
.pillar-card__summary { margin: 0; color: var(--c-ink-soft); }
.pillar-card__topics { margin: 0; padding-left: 1.15rem; color: var(--c-ink-soft); }
.pillar-card__topics li { margin: 0.15rem 0; }
.pillar-card__topics a { color: var(--c-ink); }
.pillar-card__cta {
  margin-top: auto;
  align-self: flex-start;
  display: inline-flex; align-items: center; gap: 0.4rem;
  color: var(--pillar-color);
  font-weight: 600;
  text-decoration: none;
}
.pillar-card__cta:hover { text-decoration: underline; text-underline-offset: 4px; }
.pillar-card__cta .icon { width: 1rem; height: 1rem; }

/* ----------------------- Article ----------------------- */
.article { padding-block: var(--sp-3) var(--sp-7); }
.article__container {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--sp-6);
}

.breadcrumb { font-size: var(--fs-small); color: var(--c-muted); }
.breadcrumb ol { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: 0.35rem; }
.breadcrumb li { display: inline-flex; align-items: center; }
.breadcrumb li + li::before { content: "›"; margin: 0 0.45rem; color: var(--c-muted); }
.breadcrumb a { color: var(--c-ink-soft); text-decoration: none; }
.breadcrumb a:hover { color: var(--pillar-color); text-decoration: underline; text-underline-offset: 3px; }
.breadcrumb [aria-current="page"] { color: var(--c-ink); font-weight: 600; }

.article__body { max-width: 100%; }

/* Markdown content */
.markdown-body {
  font-size: var(--fs-body);
  line-height: 1.72;
}
.markdown-body > * { max-width: 100%; }

.markdown-body h1 {
  font-size: var(--fs-h1);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.02em;
  margin: 0 0 var(--sp-5);
  background: linear-gradient(90deg, var(--pillar-color), color-mix(in srgb, var(--pillar-color) 40%, var(--c-accent)));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.markdown-body h2,
.markdown-body h3,
.markdown-body h4 {
  scroll-margin-top: calc(var(--header-h) + 1rem);
  position: relative;
  margin-top: var(--sp-7);
  margin-bottom: var(--sp-3);
  font-weight: 700;
  color: var(--c-ink);
  padding-left: 0.85rem;
}
.markdown-body h2 { font-size: var(--fs-h2); }
.markdown-body h3 { font-size: var(--fs-h3); }
.markdown-body h4 { font-size: var(--fs-h4); }
.markdown-body h2::before,
.markdown-body h3::before,
.markdown-body h4::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.45em;
  bottom: 0.45em;
  width: 3px;
  border-radius: 3px;
  background: var(--pillar-color);
}
.markdown-body h3::before { background: color-mix(in srgb, var(--pillar-color) 60%, var(--c-accent)); }
.markdown-body h4::before { background: var(--c-accent); }
.markdown-body h2 a.header-anchor,
.markdown-body h3 a.header-anchor,
.markdown-body h4 a.header-anchor {
  color: inherit;
  text-decoration: none;
}
.markdown-body h2 a.header-anchor:hover,
.markdown-body h3 a.header-anchor:hover {
  color: var(--pillar-color);
}

.markdown-body p { margin: 0 0 var(--sp-4); }
.markdown-body strong { color: var(--c-ink); font-weight: 700; }
.markdown-body ul, .markdown-body ol { margin: 0 0 var(--sp-4); padding-left: 1.4rem; }
.markdown-body li { margin: 0.25rem 0; }
.markdown-body blockquote {
  margin: var(--sp-4) 0;
  padding: var(--sp-3) var(--sp-4);
  border-left: 4px solid var(--pillar-color);
  background: var(--c-surface-tint);
  border-radius: 0 var(--rad-2) var(--rad-2) 0;
  color: var(--c-ink-soft);
}
.markdown-body hr {
  border: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--c-line), transparent);
  margin: var(--sp-6) 0;
}

/* Links inside content */
.markdown-body a {
  color: var(--pillar-color);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
  transition: text-decoration-thickness 0.15s ease, color 0.15s ease;
}
.markdown-body a:hover {
  color: color-mix(in srgb, var(--pillar-color) 70%, var(--c-ink));
  text-decoration-thickness: 2px;
}

/* Inline code */
.markdown-body :not(pre) > code {
  font-family: var(--ff-mono);
  font-size: 0.9em;
  background: color-mix(in srgb, var(--pillar-color) 9%, var(--c-bg-soft));
  color: color-mix(in srgb, var(--pillar-color) 55%, var(--c-ink));
  padding: 0.08em 0.4em;
  border-radius: 5px;
  border: 0;
  white-space: break-spaces;
}

/* Code blocks */
.code-block {
  position: relative;
  margin: var(--sp-4) 0;
  border-radius: var(--rad-2);
  background: var(--c-bg-soft);
  border: 1px solid var(--c-line);
  box-shadow: var(--shadow-1);
  overflow: hidden;
}
.code-block__toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.45rem 0.75rem;
  background: var(--c-surface-tint);
  border-bottom: 1px solid var(--c-line);
  font-family: var(--ff-mono);
  font-size: 0.78rem;
  color: var(--c-muted);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}
.code-block__lang { font-weight: 600; }
.code-block__copy {
  appearance: none;
  border: 1px solid var(--c-line);
  background: var(--c-surface);
  color: var(--c-ink-soft);
  padding: 0.25rem 0.6rem;
  border-radius: var(--rad-1);
  font: inherit;
  font-size: 0.72rem;
  cursor: pointer;
  letter-spacing: 0.04em;
  transition: background 0.15s ease, color 0.15s ease, border-color 0.15s ease, transform 0.1s ease;
}
.code-block__copy:hover { background: var(--c-primary-tint); color: var(--c-primary); border-color: var(--c-primary-soft); }
.code-block__copy:active { transform: scale(0.97); }
.code-block__copy.is-copied { background: color-mix(in srgb, var(--c-leaf) 18%, white); color: var(--c-leaf); border-color: var(--c-leaf-soft); }

.code-block pre {
  margin: 0;
  padding: 1rem 1.1rem;
  overflow-x: auto;
  font-family: var(--ff-mono);
  font-size: 0.88rem;
  line-height: 1.6;
  background: transparent;
  color: var(--c-ink);
}
.code-block pre code { font-family: inherit; }

/* highlight.js light tokens, tuned to palette */
.hljs { color: var(--c-ink); background: transparent; }
.hljs-comment, .hljs-quote { color: #7a8b95; font-style: italic; }
.hljs-keyword, .hljs-selector-tag, .hljs-literal, .hljs-section, .hljs-link { color: var(--c-primary); font-weight: 600; }
.hljs-string, .hljs-attr, .hljs-symbol, .hljs-bullet, .hljs-addition { color: var(--c-leaf); }
.hljs-number, .hljs-meta { color: var(--c-accent); }
.hljs-title, .hljs-name, .hljs-selector-id, .hljs-selector-class { color: #2a5b9c; }
.hljs-built_in, .hljs-type { color: #8e4ec6; }
.hljs-variable, .hljs-template-variable { color: var(--c-ink); }
.hljs-tag { color: var(--c-primary); }
.hljs-deletion { color: var(--c-danger); }

/* Mermaid */
.mermaid {
  margin: var(--sp-4) 0;
  padding: var(--sp-4);
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: var(--rad-2);
  overflow: auto;
  font-family: var(--ff-sans) !important;
}

/* Tables */
.table-wrap {
  margin: var(--sp-4) 0;
  overflow-x: auto;
  border-radius: var(--rad-2);
  border: 1px solid var(--c-line);
  background: var(--c-surface);
  box-shadow: var(--shadow-1);
}
.table-wrap:focus { outline: 2px solid var(--pillar-color); outline-offset: 2px; }
.markdown-body table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95em;
}
.markdown-body thead th {
  background: var(--c-surface-tint);
  color: var(--c-ink);
  text-align: left;
  font-weight: 700;
  padding: 0.7rem 0.9rem;
  border-bottom: 1px solid var(--c-line);
  position: sticky;
  top: 0;
}
.markdown-body tbody td {
  padding: 0.65rem 0.9rem;
  border-bottom: 1px solid var(--c-line);
  vertical-align: top;
}
.markdown-body tbody tr:nth-child(even) td { background: var(--c-bg-soft); }
.markdown-body tbody tr:last-child td { border-bottom: 0; }
.markdown-body tbody tr:hover td { background: color-mix(in srgb, var(--pillar-color) 7%, var(--c-surface)); }

/* Task list checkboxes */
.markdown-body ul.task-list { list-style: none; padding-left: 0.25rem; }
.markdown-body li.task-list-item {
  list-style: none;
  padding-left: 0;
  margin: 0.35rem 0;
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
}
.markdown-body li.task-list-item::marker { content: ""; }
.markdown-body li.task-list-item input[type="checkbox"].task-list-checkbox {
  appearance: none;
  -webkit-appearance: none;
  width: 1.05rem;
  height: 1.05rem;
  border-radius: 5px;
  border: 1.5px solid var(--c-line);
  background: var(--c-surface);
  display: inline-grid;
  place-items: center;
  cursor: pointer;
  flex: none;
  transform: translateY(0.15em);
  transition: background 0.15s ease, border-color 0.15s ease;
}
.markdown-body li.task-list-item input[type="checkbox"].task-list-checkbox::before {
  content: "";
  width: 0.55rem;
  height: 0.55rem;
  background: var(--pillar-color);
  border-radius: 2px;
  transform: scale(0);
  transition: transform 0.15s ease;
}
.markdown-body li.task-list-item input[type="checkbox"].task-list-checkbox:checked {
  border-color: var(--pillar-color);
  background: color-mix(in srgb, var(--pillar-color) 8%, white);
}
.markdown-body li.task-list-item input[type="checkbox"].task-list-checkbox:checked::before { transform: scale(1); }
.markdown-body li.task-list-item.is-checked,
.markdown-body li.task-list-item:has(input[type="checkbox"]:checked) {
  text-decoration: line-through;
  color: var(--c-muted);
}

/* FAQ accordions */
.markdown-body details.faq,
.markdown-body details {
  margin: 0.5rem 0;
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: var(--rad-2);
  overflow: hidden;
  transition: box-shadow 0.18s ease;
}
.markdown-body details + details { margin-top: 0.5rem; }
.markdown-body details[open] { box-shadow: var(--shadow-1); }
.markdown-body details > summary {
  cursor: pointer;
  list-style: none;
  padding: 0.85rem 1rem;
  font-weight: 600;
  color: var(--c-ink);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}
.markdown-body details > summary::-webkit-details-marker { display: none; }
.markdown-body details > summary::after {
  content: "";
  width: 0.55rem; height: 0.55rem;
  border-right: 2px solid var(--pillar-color);
  border-bottom: 2px solid var(--pillar-color);
  transform: rotate(45deg);
  transition: transform 0.18s ease;
  flex: none;
}
.markdown-body details[open] > summary::after { transform: rotate(-135deg); }
.markdown-body details > summary:hover { color: var(--pillar-color); }
.markdown-body details > *:not(summary) { padding: 0 1rem 0.9rem; }

/* KaTeX */
.markdown-body .katex { font-size: 1.05em; }
.markdown-body .katex-display { margin: var(--sp-4) 0; padding: var(--sp-3); background: var(--c-surface); border: 1px solid var(--c-line); border-radius: var(--rad-2); overflow-x: auto; }

/* ----------------------- Related sections ----------------------- */
.related { margin-top: var(--sp-7); }
.related__title { font-size: var(--fs-h3); margin: 0 0 var(--sp-4); position: relative; padding-left: 0.85rem; }
.related__title::before {
  content: ""; position: absolute; left: 0; top: 0.45em; bottom: 0.45em; width: 4px;
  border-radius: 3px;
  background: linear-gradient(180deg, var(--pillar-color), color-mix(in srgb, var(--pillar-color) 30%, var(--c-accent)));
}
.related__grid {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: var(--sp-4);
  grid-template-columns: 1fr;
}
@media (min-width: 720px) { .related__grid { grid-template-columns: repeat(2, 1fr); } }
.related__card a {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  padding: var(--sp-4);
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: var(--rad-2);
  text-decoration: none;
  color: var(--c-ink);
  transition: transform 0.18s ease, border-color 0.18s ease, box-shadow 0.18s ease;
  height: 100%;
}
.related__card a:hover {
  transform: translateY(-3px);
  border-color: color-mix(in srgb, var(--pillar-color) 50%, var(--c-line));
  box-shadow: var(--shadow-2);
}
.related__card-title { font-weight: 700; color: var(--c-ink); }
.related__card-desc { color: var(--c-ink-soft); font-size: 0.95rem; }
.related__card-cta {
  margin-top: auto;
  color: var(--pillar-color);
  font-weight: 600;
  display: inline-flex; align-items: center; gap: 0.3rem;
  font-size: 0.92rem;
}
.related__card-cta .icon { width: 1rem; height: 1rem; }

.related__list { list-style: none; padding: 0; margin: 0; display: flex; flex-wrap: wrap; gap: 0.5rem; }
.related__list a {
  display: inline-block;
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  color: var(--c-ink-soft);
  text-decoration: none;
  font-size: 0.9rem;
}
.related__list a:hover { color: var(--pillar-color); border-color: var(--pillar-color); }

.article__pillar-back {
  margin-top: var(--sp-6);
}
.article__pillar-back a {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  color: var(--pillar-color);
  text-decoration: none;
  font-weight: 600;
}
.article__pillar-back a:hover { text-decoration: underline; text-underline-offset: 4px; }

/* ----------------------- Footer ----------------------- */
.site-footer {
  flex: none;
  margin-top: var(--sp-7);
  background: linear-gradient(180deg, transparent, color-mix(in srgb, var(--c-primary) 6%, var(--c-bg)) 50%);
  border-top: 1px solid var(--c-line);
}
.site-footer__inner { padding-block: var(--sp-7); display: flex; flex-direction: column; gap: var(--sp-6); }
.site-footer__brand { display: flex; gap: var(--sp-4); align-items: center; }
.site-footer__brand .logo-mark { width: 48px; height: 48px; flex: none; }
.site-footer__name { margin: 0; font-weight: 700; color: var(--c-ink); }
.site-footer__desc { margin: 0; color: var(--c-ink-soft); max-width: 70ch; }
.site-footer__nav { display: grid; gap: var(--sp-5); grid-template-columns: 1fr; }
@media (min-width: 720px) { .site-footer__nav { grid-template-columns: repeat(3, 1fr); } }
.site-footer__heading {
  --pillar-color: var(--c-primary);
  font-size: 0.95rem;
  font-weight: 700;
  margin: 0 0 var(--sp-3);
  color: var(--pillar-color);
}
.site-footer__heading a {
  color: inherit;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
}
.site-footer__heading a:hover { text-decoration: underline; text-underline-offset: 4px; }
.site-footer__heading .icon { width: 1rem; height: 1rem; }
.site-footer__col ul { list-style: none; padding: 0; margin: 0; display: flex; flex-direction: column; gap: 0.25rem; }
.site-footer__col a { color: var(--c-ink-soft); text-decoration: none; font-size: 0.93rem; }
.site-footer__col a:hover { color: var(--c-ink); text-decoration: underline; text-underline-offset: 3px; }
.site-footer__legal { color: var(--c-muted); font-size: 0.85rem; margin: 0; }

/* Pillar hub header treatment */
.article--pillar .markdown-body > h1 {
  font-size: clamp(2.3rem, 1.6rem + 2.4vw, 3.5rem);
}

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