/* =====================================================================
   ClickHouse Analytics Pipeline — design system
   Light, elegant, professional. Indigo base with teal + pink accents.
   ===================================================================== */

:root {
  /* Palette */
  --indigo-900: #1f2353;
  --indigo-700: #2b2f78;
  --indigo-600: #3a3f9e;
  --indigo-500: #4046b8;
  --indigo-100: #e9eafc;
  --teal-600: #0e9aa7;
  --teal-400: #2bc4cf;
  --teal-100: #e2f7f8;
  --pink-600: #e0529c;
  --pink-100: #fde6f1;

  --ink: #1d2030;
  --ink-soft: #4a4f63;
  --ink-faint: #8089a3;
  --muted: #6b7187;
  --line: #e4e7f0;
  --line-strong: #d2d7e6;
  --bg: #f7f9fc;
  --surface: #ffffff;
  --surface-2: #f1f4fb;
  --code-bg: #f5f7fd;
  --code-inline-bg: #eef1fb;

  --accent: var(--indigo-600);

  /* Type */
  --font-sans: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, "SF Mono", "Cascadia Code", Menlo, Consolas, monospace;

  --step--1: clamp(0.83rem, 0.8rem + 0.15vw, 0.92rem);
  --step-0: clamp(1rem, 0.96rem + 0.2vw, 1.08rem);
  --step-1: clamp(1.2rem, 1.12rem + 0.4vw, 1.4rem);
  --step-2: clamp(1.45rem, 1.3rem + 0.7vw, 1.85rem);
  --step-3: clamp(1.8rem, 1.55rem + 1.2vw, 2.6rem);
  --step-4: clamp(2.2rem, 1.8rem + 2vw, 3.6rem);

  /* Layout */
  --container: 1320px;
  --measure: 78ch;
  --radius: 14px;
  --radius-sm: 9px;
  --header-h: 68px;
  --shadow-sm: 0 1px 2px rgba(31, 35, 83, 0.06), 0 1px 3px rgba(31, 35, 83, 0.08);
  --shadow-md: 0 6px 18px rgba(31, 35, 83, 0.08), 0 2px 6px rgba(31, 35, 83, 0.06);
  --shadow-lg: 0 18px 48px rgba(31, 35, 83, 0.14);
  --transition: 180ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--step-0);
  line-height: 1.7;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

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

/* ------------------------------ Layout ------------------------------ */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: clamp(1rem, 3vw, 2.5rem);
}

.site-main { flex: 1 0 auto; width: 100%; }

/* Anchor offset so in-page links clear the sticky header */
:target { scroll-margin-top: calc(var(--header-h) + 1rem); }
h1, h2, h3, h4 { scroll-margin-top: calc(var(--header-h) + 1rem); }

/* --------------------------- Typography ---------------------------- */
h1, h2, h3, h4 {
  font-weight: 750;
  line-height: 1.2;
  color: var(--indigo-900);
  letter-spacing: -0.01em;
}

a {
  color: var(--indigo-600);
  text-decoration: none;
  text-underline-offset: 3px;
  transition: color var(--transition), background var(--transition);
}
a:hover { color: var(--pink-600); text-decoration: underline; }
a:focus-visible,
button:focus-visible,
input:focus-visible,
summary:focus-visible {
  outline: 3px solid var(--teal-400);
  outline-offset: 2px;
  border-radius: 4px;
}

/* --------------------------- Header -------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--line);
}
.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  height: var(--header-h);
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 800;
  color: var(--indigo-900);
  letter-spacing: -0.02em;
}
.brand:hover { color: var(--indigo-900); text-decoration: none; }
.brand svg { width: 36px; height: 36px; transition: transform var(--transition); filter: drop-shadow(0 2px 5px rgba(58, 63, 158, 0.25)); }
.brand:hover svg { transform: rotate(-6deg) scale(1.06); }
.brand__text { font-size: 1.02rem; line-height: 1.05; }
.brand__text small { display: block; font-size: 0.66rem; font-weight: 600; color: var(--teal-600); letter-spacing: 0.04em; text-transform: uppercase; }

.nav { display: flex; align-items: center; gap: 0.35rem; }
.nav a {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 0.8rem;
  border-radius: 999px;
  color: var(--ink-soft);
  font-weight: 600;
  font-size: 0.95rem;
}
.nav a svg { width: 18px; height: 18px; }
.nav a:hover { color: var(--indigo-700); background: var(--indigo-100); text-decoration: none; }
.nav a[aria-current="page"] {
  color: var(--indigo-700);
  background: var(--indigo-100);
  box-shadow: inset 0 0 0 1px var(--line-strong);
}

.nav-toggle { display: none; }

/* --------------------------- Footer -------------------------------- */
.site-footer {
  flex-shrink: 0;
  margin-top: 4rem;
  background: var(--indigo-900);
  color: #c9cdf0;
}
.site-footer a { color: #dfe2ff; }
.site-footer a:hover { color: #fff; }
.site-footer__inner {
  display: grid;
  grid-template-columns: 1.4fr repeat(3, 1fr);
  gap: 2rem;
  padding-block: 3rem 2rem;
}
.site-footer__brand { display: flex; gap: 0.7rem; align-items: flex-start; }
.site-footer__brand svg { width: 40px; height: 40px; flex: none; }
.site-footer h4 { color: #fff; font-size: 0.82rem; text-transform: uppercase; letter-spacing: 0.06em; margin: 0 0 0.8rem; }
.site-footer ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.5rem; }
.site-footer__bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.12);
  padding-block: 1.2rem;
  font-size: 0.85rem;
  color: #9aa0cf;
}

/* --------------------------- Buttons ------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  padding: 0.75rem 1.3rem;
  border-radius: 999px;
  font-weight: 650;
  font-size: 0.98rem;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition), background var(--transition);
}
.btn svg { width: 20px; height: 20px; }
.btn--primary { background: linear-gradient(120deg, var(--indigo-600), var(--indigo-500)); color: #fff; box-shadow: var(--shadow-md); }
.btn--primary:hover { color: #fff; text-decoration: none; transform: translateY(-2px); box-shadow: var(--shadow-lg); }
.btn--ghost { background: var(--surface); color: var(--indigo-700); border-color: var(--line-strong); box-shadow: var(--shadow-sm); }
.btn--ghost:hover { color: var(--indigo-700); text-decoration: none; transform: translateY(-2px); box-shadow: var(--shadow-md); border-color: var(--teal-400); }

/* --------------------------- Home ---------------------------------- */
.hero { text-align: center; padding-block: clamp(2.5rem, 6vw, 5rem) clamp(2rem, 4vw, 3rem); }
.hero__logo { display: block; width: clamp(110px, 18vw, 168px); height: auto; margin: 0 auto 1.6rem; filter: drop-shadow(0 12px 30px rgba(58, 63, 158, 0.28)); transition: transform var(--transition); }
.hero__logo:hover { transform: translateY(-4px) scale(1.02); }
.hero h1 { font-size: var(--step-4); margin: 0 0 0.4rem; }
.hero__tagline { color: var(--teal-600); font-weight: 700; letter-spacing: 0.02em; margin: 0 0 1.4rem; font-size: var(--step-1); }
.hero__lead { max-width: 70ch; margin: 0 auto 1rem; color: var(--ink-soft); font-size: 1.1rem; }
.hero__lead:last-of-type { margin-bottom: 2rem; }

.cta-row { display: flex; flex-wrap: wrap; gap: 0.9rem; justify-content: center; }
.cta {
  display: inline-flex;
  align-items: center;
  gap: 0.7rem;
  padding: 0.85rem 1.4rem;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--line);
  box-shadow: var(--shadow-sm);
  font-weight: 650;
  color: var(--indigo-900);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.cta:hover { color: var(--indigo-900); text-decoration: none; transform: translateY(-3px); box-shadow: var(--shadow-md); }
.cta__icon { display: inline-grid; place-items: center; width: 40px; height: 40px; border-radius: 11px; color: #fff; flex: none; }
.cta__icon svg { width: 22px; height: 22px; }

.section-head { text-align: center; max-width: 64ch; margin: 0 auto clamp(1.5rem, 3vw, 2.5rem); }
.section-head h2 { font-size: var(--step-3); margin: 0 0 0.5rem; }
.section-head p { color: var(--ink-soft); margin: 0; font-size: 1.05rem; }

.pillar-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 1.4rem; }
.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.6rem;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
  position: relative;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}
.card::before { content: ""; position: absolute; inset: 0 0 auto 0; height: 4px; background: var(--card-accent, var(--indigo-500)); }
.card:hover { transform: translateY(-5px); box-shadow: var(--shadow-lg); border-color: transparent; }
.card__icon { display: inline-grid; place-items: center; width: 48px; height: 48px; border-radius: 13px; color: #fff; margin-bottom: 1rem; background: var(--card-accent, var(--indigo-500)); }
.card__icon svg { width: 26px; height: 26px; }
.card h3 { margin: 0 0 0.5rem; font-size: var(--step-1); }
.card h3 a { color: inherit; }
.card h3 a:hover { color: var(--card-accent, var(--pink-600)); text-decoration: none; }
.card p { margin: 0 0 1rem; color: var(--ink-soft); font-size: 0.97rem; }
.card__links { list-style: none; margin: auto 0 0; padding: 0; display: grid; gap: 0.35rem; font-size: 0.92rem; }
.card__links a { display: inline-flex; align-items: center; gap: 0.4rem; }
.card__links a::before { content: "›"; color: var(--card-accent, var(--teal-600)); font-weight: 800; }

.home-section { padding-block: clamp(2rem, 5vw, 3.5rem); }
.home-section--alt { background: var(--surface-2); border-block: 1px solid var(--line); }

/* --------------------------- Breadcrumbs --------------------------- */
.breadcrumbs { display: flex; flex-wrap: wrap; gap: 0.35rem; align-items: center; font-size: 0.85rem; color: var(--muted); padding-block: 1.4rem 0.4rem; }
.breadcrumbs ol { display: contents; list-style: none; margin: 0; padding: 0; }
.breadcrumbs li { display: inline-flex; align-items: center; gap: 0.35rem; }
.breadcrumbs li:not(:last-child)::after { content: "/"; color: var(--line-strong); margin-left: 0.35rem; }
.breadcrumbs a { color: var(--muted); font-weight: 600; }
.breadcrumbs a:hover { color: var(--indigo-600); }
.breadcrumbs [aria-current="page"] { color: var(--ink); font-weight: 700; }

/* --------------------------- Article ------------------------------- */
.article-shell { display: grid; grid-template-columns: minmax(0, 1fr) 260px; gap: clamp(1.5rem, 4vw, 3.5rem); align-items: start; padding-block: 1rem 3rem; }
.toc { position: sticky; top: calc(var(--header-h) + 1.2rem); align-self: start; font-size: 0.9rem; max-height: calc(100vh - var(--header-h) - 3rem); overflow: auto; }
.toc h2 { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.07em; color: var(--muted); margin: 0 0 0.7rem; }
.toc ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.15rem; border-left: 2px solid var(--line); }
.toc li.lvl-3 a { padding-left: 1.6rem; font-size: 0.85rem; color: var(--muted); }
.toc a { display: block; padding: 0.25rem 0.8rem; color: var(--ink-soft); border-left: 2px solid transparent; margin-left: -2px; border-radius: 0 6px 6px 0; }
.toc a:hover { color: var(--indigo-700); background: var(--indigo-100); text-decoration: none; }
.toc a.is-active { color: var(--indigo-700); border-left-color: var(--indigo-600); background: var(--indigo-100); font-weight: 650; }

.article-header h1 { font-size: var(--step-3); margin: 0.3rem 0 0.6rem; background: linear-gradient(115deg, var(--indigo-600), var(--teal-600) 60%, var(--pink-600)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.article-meta { color: var(--muted); font-size: 0.9rem; margin-bottom: 1.4rem; display: flex; gap: 0.6rem; flex-wrap: wrap; align-items: center; }
.chip { display: inline-flex; align-items: center; gap: 0.35rem; padding: 0.2rem 0.7rem; border-radius: 999px; background: var(--teal-100); color: var(--teal-600); font-weight: 650; font-size: 0.78rem; }
.chip svg { width: 14px; height: 14px; flex: none; }

/* The prose fills the full width of its column (not the full page, not a narrow column) */
.prose { max-width: 100%; font-size: 1.05rem; }
.prose > * + * { margin-top: 1.15rem; }
.prose h1 {
  font-size: var(--step-3);
  margin-top: 0.2rem;
  background: linear-gradient(115deg, var(--indigo-600), var(--teal-600) 55%, var(--pink-600));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.prose h2 { font-size: var(--step-2); margin-top: 2.4rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--line); }
.prose h2::before { content: ""; display: inline-block; width: 0.6rem; height: 1.1rem; margin-right: 0.55rem; vertical-align: -0.12em; border-radius: 3px; background: linear-gradient(var(--teal-600), var(--indigo-600)); }
.prose h3 { font-size: var(--step-1); margin-top: 1.9rem; color: var(--indigo-700); }
.prose h4 { font-size: 1.05rem; margin-top: 1.5rem; color: var(--indigo-700); }
.prose p, .prose li { color: var(--ink-soft); }
.prose strong { color: var(--ink); }
.prose ul, .prose ol { padding-left: 1.4rem; }
.prose li + li { margin-top: 0.4rem; }
.prose a { font-weight: 600; border-bottom: 1px solid color-mix(in srgb, var(--indigo-600) 30%, transparent); }
.prose a:hover { border-bottom-color: var(--pink-600); }
.prose blockquote { margin: 1.4rem 0; padding: 0.6rem 1.2rem; border-left: 4px solid var(--teal-400); background: var(--teal-100); border-radius: 0 var(--radius-sm) var(--radius-sm) 0; color: var(--ink-soft); }
.prose hr { border: none; border-top: 1px solid var(--line); margin: 2.5rem 0; }

/* Inline code: subtle tint, no border, blends with text */
.prose :not(pre) > code {
  font-family: var(--font-mono);
  font-size: 0.86em;
  background: var(--code-inline-bg);
  color: var(--indigo-700);
  padding: 0.12em 0.4em;
  border-radius: 5px;
  word-break: break-word;
}

/* --------------------------- Code blocks --------------------------- */
.code-block {
  margin: 1.6rem 0;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  overflow: hidden;
  background: var(--code-bg);
  box-shadow: var(--shadow-sm);
}
.code-block__bar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 0.4rem 0.55rem 0.4rem 0.9rem;
  background: var(--surface-2);
  border-bottom: 1px solid var(--line);
}
.code-block__lang { font-family: var(--font-mono); font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--muted); font-weight: 700; }
.code-block__copy {
  display: inline-flex; align-items: center; gap: 0.35rem;
  border: 1px solid var(--line-strong); background: var(--surface);
  color: var(--ink-soft); font-size: 0.78rem; font-weight: 650;
  padding: 0.3rem 0.6rem; border-radius: 7px; cursor: pointer;
  transition: all var(--transition);
}
.code-block__copy:hover { color: var(--indigo-700); border-color: var(--teal-400); background: var(--indigo-100); }
.code-block__copy.is-copied { color: var(--teal-600); border-color: var(--teal-400); background: var(--teal-100); }
.code-block pre { margin: 0; padding: 1.1rem 1.2rem; overflow-x: auto; font-family: var(--font-mono); font-size: 0.86rem; line-height: 1.6; }
.code-block code { font-family: var(--font-mono); }

/* --------------------------- Tables -------------------------------- */
.table-wrap { overflow-x: auto; margin: 1.6rem 0; border: 1px solid var(--line); border-radius: var(--radius-sm); box-shadow: var(--shadow-sm); -webkit-overflow-scrolling: touch; }
table { border-collapse: collapse; width: 100%; min-width: 520px; font-size: 0.95rem; }
thead th { background: var(--indigo-600); color: #fff; text-align: left; font-weight: 650; padding: 0.7rem 1rem; white-space: nowrap; }
tbody td { padding: 0.65rem 1rem; border-top: 1px solid var(--line); color: var(--ink-soft); vertical-align: top; }
tbody tr:nth-child(even) { background: var(--surface-2); }
tbody tr:hover { background: var(--indigo-100); }

/* --------------------- Task-list checkboxes ------------------------ */
.prose ul .task-list-item,
.prose .task-list-item { list-style: none; position: relative; padding-left: 0.2rem; }
.prose ul:has(> .task-list-item) { padding-left: 0.6rem; }
.task-list-item input[type="checkbox"] {
  appearance: none; -webkit-appearance: none;
  width: 1.15em; height: 1.15em; margin: 0 0.55em -0.2em 0;
  border: 2px solid var(--line-strong); border-radius: 5px;
  background: var(--surface); cursor: pointer; vertical-align: middle;
  transition: all var(--transition); flex: none;
}
.task-list-item input[type="checkbox"]:hover { border-color: var(--teal-400); }
.task-list-item input[type="checkbox"]:checked {
  background: var(--teal-600); border-color: var(--teal-600);
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'%3E%3Cpath fill='none' stroke='white' stroke-width='3.5' stroke-linecap='round' stroke-linejoin='round' d='M5 13l4 4L19 7'/%3E%3C/svg%3E");
  background-size: 80%; background-position: center; background-repeat: no-repeat;
}
.task-list-item.is-checked { color: var(--muted); text-decoration: line-through; text-decoration-color: var(--line-strong); }

/* --------------------------- Accordions (FAQ) ---------------------- */
.faq details, details.accordion {
  border: 1px solid var(--line); border-radius: var(--radius-sm);
  margin: 0.7rem 0; background: var(--surface); box-shadow: var(--shadow-sm); overflow: hidden;
}
.faq summary, details.accordion summary {
  cursor: pointer; list-style: none; padding: 1rem 1.2rem;
  font-weight: 650; color: var(--indigo-900); display: flex; align-items: center; justify-content: space-between; gap: 1rem;
}
.faq summary::-webkit-details-marker, details.accordion summary::-webkit-details-marker { display: none; }
.faq summary::after, details.accordion summary::after {
  content: ""; width: 11px; height: 11px; border-right: 2.5px solid var(--teal-600); border-bottom: 2.5px solid var(--teal-600);
  transform: rotate(45deg); transition: transform var(--transition); flex: none;
}
.faq details[open] summary::after, details.accordion[open] summary::after { transform: rotate(-135deg); }
.faq summary:hover, details.accordion summary:hover { background: var(--indigo-100); }
.faq details > *:not(summary), details.accordion > *:not(summary) { padding: 0 1.2rem 1.1rem; color: var(--ink-soft); margin-top: 0; }

/* --------------------------- Mermaid ------------------------------- */
.mermaid { position: relative; margin: 1.8rem 0; text-align: center; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 1.2rem; box-shadow: var(--shadow-sm); overflow-x: auto; transition: box-shadow var(--transition), border-color var(--transition); }
.mermaid:not([data-processed]) { color: transparent; min-height: 60px; }
.mermaid[data-expandable] { cursor: zoom-in; }
.mermaid[data-expandable]:hover { border-color: var(--teal-400); box-shadow: var(--shadow-md); }
.mermaid[data-expandable]:focus-visible { outline: 3px solid var(--teal-400); outline-offset: 2px; }
.mermaid svg { max-width: 100%; height: auto; }

/* Expand affordance */
.viz-expand {
  position: absolute; top: 0.6rem; right: 0.6rem;
  display: inline-flex; align-items: center; gap: 0.35rem;
  padding: 0.3rem 0.6rem; border-radius: 999px;
  border: 1px solid var(--line-strong); background: rgba(255, 255, 255, 0.9);
  color: var(--indigo-700); font: inherit; font-size: 0.74rem; font-weight: 650;
  cursor: pointer; opacity: 0; transform: translateY(-4px);
  transition: opacity var(--transition), transform var(--transition), background var(--transition);
  backdrop-filter: blur(4px);
}
.mermaid:hover .viz-expand,
.mermaid:focus-within .viz-expand { opacity: 1; transform: translateY(0); }
.viz-expand:hover { background: var(--indigo-100); border-color: var(--teal-400); }
@media (hover: none) { .viz-expand { opacity: 1; transform: none; } }

/* Full-screen diagram modal */
body.viz-locked { overflow: hidden; }
.viz-modal { position: fixed; inset: 0; z-index: 1000; display: grid; place-items: center; padding: clamp(0.8rem, 3vw, 2.5rem); }
.viz-modal[hidden] { display: none; }
.viz-modal__backdrop { position: absolute; inset: 0; background: rgba(20, 23, 55, 0.62); backdrop-filter: blur(3px); animation: viz-fade 160ms ease-out; }
.viz-modal__dialog {
  position: relative; z-index: 1; width: min(1500px, 96vw); max-height: 94vh;
  background: var(--surface); border-radius: var(--radius); box-shadow: var(--shadow-lg);
  padding: clamp(1rem, 3vw, 2.4rem); overflow: auto; animation: viz-pop 180ms cubic-bezier(0.2, 0.7, 0.3, 1);
}
.viz-modal__body { display: grid; place-items: center; }
.viz-modal__body svg { width: 100%; height: auto; }
.viz-modal__close {
  position: absolute; top: 0.7rem; right: 0.7rem; z-index: 2;
  display: inline-grid; place-items: center; width: 42px; height: 42px;
  border-radius: 50%; border: 1px solid var(--line); background: var(--surface);
  color: var(--ink-soft); cursor: pointer; box-shadow: var(--shadow-sm);
  transition: all var(--transition);
}
.viz-modal__close:hover { color: var(--pink-600); border-color: var(--pink-600); transform: rotate(90deg); }
@keyframes viz-fade { from { opacity: 0; } to { opacity: 1; } }
@keyframes viz-pop { from { opacity: 0; transform: scale(0.96); } to { opacity: 1; transform: scale(1); } }
@media (prefers-reduced-motion: reduce) { .viz-modal__backdrop, .viz-modal__dialog { animation: none; } }

/* --------------------------- Child / related nav ------------------- */
.subnav { margin-top: 3rem; }
.subnav h2 { font-size: var(--step-1); margin-bottom: 1rem; }
.subnav__grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 1rem; }
.subnav__card { display: block; padding: 1.1rem 1.2rem; border: 1px solid var(--line); border-radius: var(--radius-sm); background: var(--surface); box-shadow: var(--shadow-sm); transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition); }
.subnav__card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: var(--teal-400); text-decoration: none; }
.subnav__card strong { display: block; color: var(--indigo-900); margin-bottom: 0.3rem; }
.subnav__card span { color: var(--muted); font-size: 0.9rem; }

.pager { display: flex; justify-content: space-between; gap: 1rem; margin-top: 2.5rem; padding-top: 1.5rem; border-top: 1px solid var(--line); }

/* --------------------------- Responsive ---------------------------- */
@media (max-width: 960px) {
  .article-shell { grid-template-columns: 1fr; }
  .toc { position: static; max-height: none; order: -1; background: var(--surface-2); border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 1rem 1.2rem; margin-bottom: 1.5rem; }
  .toc ul { border-left: none; }
  .site-footer__inner { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 720px) {
  :root { --header-h: 60px; }
  .nav { position: fixed; inset: var(--header-h) 0 auto 0; flex-direction: column; align-items: stretch; gap: 0.2rem; background: var(--surface); border-bottom: 1px solid var(--line); padding: 0.8rem clamp(1rem, 3vw, 2.5rem) 1.1rem; box-shadow: var(--shadow-md); transform: translateY(-130%); transition: transform var(--transition); }
  .nav.is-open { transform: translateY(0); }
  .nav a { padding: 0.75rem 0.9rem; border-radius: var(--radius-sm); }
  .nav-toggle { display: inline-grid; place-items: center; width: 42px; height: 42px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface); cursor: pointer; color: var(--indigo-700); }
  .nav-toggle svg { width: 22px; height: 22px; }
  .prose { font-size: 1rem; }
  .site-footer__inner { grid-template-columns: 1fr; gap: 1.5rem; }
  .pager { flex-direction: column; }
}

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