:root {
  --color-surface: #fbfbfb;
  --color-surface-alt: #f1f1f1;
  --color-surface-deep: #e3e3e4;
  --color-ink: #323239;
  --color-ink-soft: #5e5e69;
  --color-ink-muted: #7a7a85;
  --color-line: #d7d7d8;
  --color-primary: #0a0af5;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #d9d9fa;
  --color-accent: #837606;
  --color-accent-ink: #ffffff;
  --color-highlight: #e5e3cf;
  --color-focus: #807200;
  --color-contrast-surface: #151531;
  --color-contrast-ink: #e4e4e7;
  --color-contrast-line: #434359;
  --color-contrast-accent: #f3db0c;
  --overlay-scrim: linear-gradient(180deg, rgba(21, 21, 49, 0.35) 0%, rgba(21, 21, 49, 0.72) 55%, rgba(21, 21, 49, 0.92) 100%);
  --font-heading: "Source Han Sans SC", "Noto Sans SC", SimHei, "Microsoft YaHei", sans-serif;
  --font-body: "PingFang SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 8.7px;
  --text-sm: 14.2px;
  --text-base: 18px;
  --text-lg: 29.1px;
  --text-xl: 47.1px;
  --text-2xl: 76.2px;
  --text-3xl: 123.4px;
  --text-4xl: 199.6px;
  --text-display: clamp(61px, 12.5vw, 160px);
  --text-figure: clamp(51px, 9.0vw, 115px);
  --weight-heading: 878;
  --weight-body: 400;
  --leading-body: 1.68;
  --leading-heading: 1.19;
  --tracking-heading: -0.031em;
  --radius-sm: 1px;
  --radius-md: 2px;
  --radius-lg: 2px;
  --radius-pill: 2px;
  --border-thin: 1px;
  --border-thick: 3px;
  --shadow-1: none;
  --shadow-2: none;
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1120px;
  --measure: 70ch;
  --gutter: 24px;
  --section-y: 98px;
  --section-y-lg: 137px;
}

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 140px;
}

body {
  margin: 0;
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6, p, figure, blockquote, dl, dd, pre { margin: 0; }
ul, ol { margin: 0; padding: 0; }
li { list-style: none; }

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

a { color: var(--color-primary); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { text-decoration: underline; }

button { font: inherit; color: inherit; background: none; border: 0; cursor: pointer; }
input, select, textarea { font: inherit; }

[hidden] { display: none !important; }

:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 2px;
}

/* ============================================================
   Layout primitives
   ============================================================ */
.shell {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.section { padding-block: var(--section-y); }
.section--lg { padding-block: var(--section-y-lg); }
.section--alt { background-color: var(--color-surface-alt); }
.section--deep {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.section--deep h2,
.section--deep h3 { color: var(--color-contrast-ink); }
.section--deep .lede { color: var(--color-contrast-ink); }
.section--deep a { color: var(--color-contrast-accent); }
.section--deep :focus-visible { outline-color: var(--color-contrast-accent); }

.grid {
  display: grid;
  gap: var(--space-3);
  grid-template-columns: repeat(auto-fit, minmax(0, 1fr));
}
.grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }

.split {
  display: grid;
  grid-template-columns: minmax(0, 7fr) minmax(0, 3fr);
  gap: var(--space-6);
  align-items: start;
}

.band {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  height: 6px;
}
.band > * { background-color: var(--color-primary); }
.band > *:nth-child(2) { background-color: var(--color-accent); }
.band > *:nth-child(3) { background-color: var(--color-primary-soft); }
.band > *:nth-child(4) { background-color: var(--color-ink-muted); }
.band > *:nth-child(5) { background-color: var(--color-line); }

/* ============================================================
   Typography
   ============================================================ */
.display,
.hero-title {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-display);
  line-height: 0.92;
  letter-spacing: var(--tracking-heading);
  text-wrap: balance;
}

.figure {
  font-family: var(--font-mono);
  font-weight: var(--weight-heading);
  font-size: var(--text-figure);
  line-height: 0.95;
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
}

.eyebrow {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 700;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-accent);
}
.section--deep .eyebrow { color: var(--color-contrast-accent); }

.lede {
  font-size: var(--text-lg);
  line-height: 1.4;
  max-width: var(--measure);
  color: var(--color-ink-soft);
}

.mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.02em;
}

.mark {
  background-color: var(--color-highlight);
  color: var(--color-ink);
  padding: 1px 6px;
  border-radius: var(--radius-sm);
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 2px 8px;
  border-radius: var(--radius-sm);
  background-color: var(--color-primary-soft);
  color: var(--color-primary);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  line-height: 1.5;
  white-space: nowrap;
}
.badge--accent {
  background-color: var(--color-accent);
  color: var(--color-accent-ink);
}
.section--deep .badge {
  background-color: transparent;
  color: var(--color-contrast-accent);
  border: var(--border-thin) solid var(--color-contrast-line);
}

.prose {
  max-width: var(--measure);
  color: var(--color-ink);
}
.prose > * + * { margin-top: var(--space-3); }
.prose h2 {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  margin-top: var(--space-6);
}
.prose h3 {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-base);
  line-height: var(--leading-heading);
  margin-top: var(--space-4);
}
.prose ul,
.prose ol { padding-left: 1.2em; }
.prose ul li { list-style: none; position: relative; }
.prose ul li::before {
  content: "";
  position: absolute;
  left: -1.1em;
  top: 0.72em;
  width: 8px;
  height: 2px;
  background-color: var(--color-accent);
}
.prose ol { counter-reset: prose-ol; }
.prose ol li { list-style: none; position: relative; counter-increment: prose-ol; }
.prose ol li::before {
  content: counter(prose-ol, decimal-leading-zero);
  position: absolute;
  left: -2.2em;
  top: 0;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}
.prose blockquote {
  border-left: var(--border-thick) solid var(--color-primary);
  padding-left: var(--space-3);
  color: var(--color-ink-soft);
}
.section--deep .prose,
.section--deep .prose blockquote { color: var(--color-contrast-ink); }

/* ============================================================
   Buttons
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  min-height: 48px;
  padding: 12px 24px;
  border: var(--border-thin) solid var(--color-ink);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: 700;
  line-height: 1.2;
  text-decoration: none;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}
.btn:hover { text-decoration: none; background-color: var(--color-surface-deep); }
.btn--primary {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}
.btn--primary:hover {
  background-color: color-mix(in srgb, var(--color-primary) 82%, var(--color-contrast-surface));
  border-color: color-mix(in srgb, var(--color-primary) 82%, var(--color-contrast-surface));
}
.btn--ghost {
  background-color: transparent;
  border-color: var(--color-line);
  color: var(--color-ink-soft);
}
.btn--ghost:hover { background-color: var(--color-surface-alt); color: var(--color-ink); }
.btn--block { display: flex; width: 100%; }
.section--deep .btn--ghost {
  border-color: var(--color-contrast-line);
  color: var(--color-contrast-ink);
}
.section--deep .btn--ghost:hover { background-color: var(--color-contrast-line); }

/* ============================================================
   Chip (used on dark surfaces)
   ============================================================ */
.chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 34px;
  padding: 6px 12px;
  border: var(--border-thin) solid var(--color-contrast-line);
  border-radius: var(--radius-sm);
  background-color: transparent;
  color: var(--color-contrast-ink);
  font-family: var(--font-body);
  font-size: var(--text-sm);
  font-weight: 400;
  line-height: 1.2;
  text-decoration: none;
  white-space: nowrap;
  transition: border-color 0.18s ease, color 0.18s ease, background-color 0.18s ease;
}
.chip:hover {
  text-decoration: none;
  border-color: var(--color-contrast-accent);
  color: var(--color-contrast-accent);
}
.chip__dot {
  width: 8px;
  height: 8px;
  flex: 0 0 auto;
  background-color: var(--color-contrast-accent);
}
.chip[aria-pressed="true"] {
  background-color: var(--color-contrast-accent);
  border-color: var(--color-contrast-accent);
  color: var(--color-contrast-surface);
}
.chip[aria-pressed="true"] .chip__dot { background-color: var(--color-contrast-surface); }

/* ============================================================
   Skip link
   ============================================================ */
.skip-link {
  position: fixed;
  top: var(--space-1);
  left: var(--space-1);
  z-index: 200;
  padding: 10px 16px;
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
  font-weight: 700;
  text-decoration: none;
  border-radius: var(--radius-sm);
  transform: translateY(-200%);
}
.skip-link:focus {
  transform: translateY(0);
  text-decoration: none;
}

/* ============================================================
   Header
   ============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 60;
}

.header-top {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
}
.header-top__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2) var(--space-3);
  min-height: 46px;
  padding-block: 6px;
}

.brand-line {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  font-size: var(--text-sm);
  letter-spacing: 0.05em;
  color: var(--color-contrast-ink);
}
.brand-line__mark { font-weight: 700; }
.brand-line__sep { color: var(--color-contrast-accent); }
.brand-line__sub { color: color-mix(in srgb, var(--color-contrast-ink) 72%, var(--color-contrast-surface)); }

.header-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1);
}

.header-main {
  position: relative;
  background-color: var(--color-surface);
  border-bottom: var(--border-thick) solid var(--color-contrast-surface);
}
.header-main__inner {
  position: relative;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-height: 74px;
}

.brand {
  display: inline-flex;
  align-items: baseline;
  gap: 10px;
  color: var(--color-ink);
  text-decoration: none;
  white-space: nowrap;
}
.brand:hover { text-decoration: none; }
.brand__mark {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: 1;
  letter-spacing: var(--tracking-heading);
}
.brand__mono {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  color: var(--color-accent);
  align-self: center;
}

.site-nav { margin-inline-start: auto; }
.site-nav__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 2px;
}
.site-nav__link {
  display: block;
  padding: 12px 14px;
  color: var(--color-ink);
  font-size: var(--text-base);
  text-decoration: none;
  border-radius: var(--radius-sm);
  transition: background-color 0.18s ease, color 0.18s ease;
}
.site-nav__link:hover {
  text-decoration: none;
  background-color: var(--color-primary-soft);
  color: var(--color-primary);
}
.site-nav__link[aria-current="page"] {
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
  font-weight: 700;
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: 10px;
  margin-inline-start: auto;
  min-height: 44px;
  padding: 8px 14px;
  border: var(--border-thin) solid var(--color-ink);
  border-radius: var(--radius-sm);
  color: var(--color-ink);
  font-size: var(--text-sm);
  font-weight: 700;
}
.nav-toggle__bars,
.nav-toggle__bars::before,
.nav-toggle__bars::after {
  display: block;
  width: 18px;
  height: 2px;
  background-color: currentColor;
  content: "";
}
.nav-toggle__bars { position: relative; }
.nav-toggle__bars::before { position: absolute; top: -6px; left: 0; }
.nav-toggle__bars::after { position: absolute; top: 6px; left: 0; }
.nav-toggle[aria-expanded="true"] {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}

.scroll-meter {
  position: absolute;
  left: 0;
  right: 0;
  bottom: calc(-1 * var(--border-thick));
  height: var(--border-thick);
  pointer-events: none;
}
.scroll-meter__bar {
  display: block;
  height: 100%;
  width: 0;
  background-color: var(--color-contrast-accent);
}

/* ============================================================
   Breadcrumb
   ============================================================ */
.breadcrumb { font-size: var(--text-sm); }
.breadcrumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  color: var(--color-ink-muted);
  padding-block: var(--space-3);
}
.breadcrumb__item { display: inline-flex; align-items: center; gap: 10px; }
.breadcrumb__item:not(:last-child)::after {
  content: "›";
  color: var(--color-line);
}
.breadcrumb__item a { color: var(--color-ink-soft); text-decoration: none; }
.breadcrumb__item a:hover { text-decoration: underline; color: var(--color-primary); }
.breadcrumb__item[aria-current="page"] { color: var(--color-ink); }

/* ============================================================
   TOC
   ============================================================ */
.toc {
  position: sticky;
  top: 152px;
  border-top: var(--border-thick) solid var(--color-contrast-surface);
  padding-top: var(--space-2);
}
.toc__title {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-accent);
  margin-bottom: var(--space-2);
}
.toc__list { display: flex; flex-direction: column; gap: 2px; }
.toc__link {
  display: block;
  padding: 8px 10px;
  border-left: var(--border-thick) solid transparent;
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  text-decoration: none;
}
.toc__link:hover { text-decoration: none; color: var(--color-primary); border-left-color: var(--color-primary-soft); }
.toc__link[aria-current="true"] {
  color: var(--color-primary);
  font-weight: 700;
  border-left-color: var(--color-primary);
  background-color: var(--color-primary-soft);
}

/* ============================================================
   Disclosure / panel / table
   ============================================================ */
.disclosure {
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface-alt);
  overflow: hidden;
}
.disclosure + .disclosure { margin-top: var(--space-2); }
.disclosure__toggle {
  display: flex;
  width: 100%;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
  padding: var(--space-3);
  text-align: left;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-base);
  line-height: var(--leading-heading);
  color: var(--color-ink);
}
.disclosure__toggle::after {
  content: "+";
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: var(--text-base);
  color: var(--color-accent);
}
.disclosure__toggle[aria-expanded="true"] { background-color: var(--color-surface-deep); }
.disclosure__toggle[aria-expanded="true"]::after { content: "–"; }
.disclosure__panel {
  padding: var(--space-2) var(--space-3) var(--space-3);
  background-color: var(--color-surface);
  border-top: var(--border-thin) solid var(--color-line);
  color: var(--color-ink-soft);
}

.panel {
  padding: var(--space-3);
  background-color: var(--color-surface-alt);
  border-radius: var(--radius-sm);
  border-left: var(--border-thick) solid var(--color-primary);
}
.section--deep .panel {
  background-color: color-mix(in srgb, var(--color-contrast-surface) 70%, var(--color-contrast-line));
  color: var(--color-contrast-ink);
}

.table {
  width: 100%;
  border-collapse: collapse;
  font-size: var(--text-base);
}
.table caption {
  text-align: left;
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  padding-bottom: var(--space-1);
}
.table th,
.table td {
  padding: 12px 14px;
  border-bottom: var(--border-thin) solid var(--color-line);
  text-align: left;
  vertical-align: top;
}
.table thead th {
  background-color: var(--color-surface-deep);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  color: var(--color-ink);
}
.table tbody tr:hover td { background-color: var(--color-surface-alt); }
.section--deep .table th,
.section--deep .table td { border-bottom-color: var(--color-contrast-line); }
.section--deep .table thead th {
  background-color: color-mix(in srgb, var(--color-contrast-surface) 60%, var(--color-contrast-line));
  color: var(--color-contrast-ink);
}

/* ============================================================
   Media containers
   ============================================================ */
.media {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-md);
  background-color: var(--color-surface-deep);
  aspect-ratio: 4 / 3;
}
.media--wide { aspect-ratio: 16 / 9; }
.media--tall { aspect-ratio: 3 / 4; }
.media--square { aspect-ratio: 1 / 1; }
.media img,
.media video {
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.media__scrim {
  position: absolute;
  inset: 0;
  background-image: var(--overlay-scrim);
  pointer-events: none;
}
.media__caption {
  position: absolute;
  inset-inline: 0;
  bottom: 0;
  padding: var(--space-3);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  line-height: 1.5;
  z-index: 1;
}

/* ============================================================
   Reveal + back to top
   ============================================================ */
html.js [data-reveal] {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}
html.js [data-reveal].is-visible {
  opacity: 1;
  transform: none;
}

.back-to-top {
  position: fixed;
  right: var(--gutter);
  bottom: var(--gutter);
  z-index: 90;
  display: none;
  align-items: center;
  gap: 8px;
  min-height: 46px;
  padding: 10px 16px;
  border: var(--border-thin) solid var(--color-contrast-accent);
  border-radius: var(--radius-sm);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-accent);
  font-size: var(--text-sm);
  font-weight: 700;
}
.back-to-top[data-visible] { display: inline-flex; }
.back-to-top:hover { background-color: var(--color-contrast-line); }

/* ============================================================
   Footer
   ============================================================ */
.site-footer {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  margin-top: var(--section-y);
}
.site-footer :focus-visible { outline-color: var(--color-contrast-accent); }

.footer-rule {
  height: 16px;
  border-top: var(--border-thin) solid var(--color-contrast-line);
  background-image: repeating-linear-gradient(
    90deg,
    var(--color-contrast-line) 0,
    var(--color-contrast-line) 1px,
    transparent 1px,
    transparent 24px
  );
}
.site-footer .band { height: 4px; }
.site-footer .band > *:nth-child(5) { background-color: var(--color-contrast-line); }

.footer-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.6fr) repeat(3, minmax(0, 1fr));
  gap: var(--space-6) var(--space-3);
  padding-block: var(--space-8) var(--space-6);
}

.footer-brand__name {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-contrast-ink);
}
.footer-brand__mono {
  margin-top: 6px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  color: var(--color-contrast-accent);
}
.footer-tag {
  margin-top: var(--space-2);
  max-width: 40ch;
  font-size: var(--text-sm);
  line-height: 1.7;
  color: color-mix(in srgb, var(--color-contrast-ink) 74%, var(--color-contrast-surface));
}
.footer-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1);
  margin-top: var(--space-3);
}

.footer-col__title {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 700;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-contrast-accent);
  padding-bottom: var(--space-2);
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
  margin-bottom: var(--space-2);
}
.footer-links { display: flex; flex-direction: column; gap: 10px; }
.footer-links a {
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  text-decoration: none;
}
.footer-links a:hover { color: var(--color-contrast-accent); text-decoration: underline; }
.footer-links--plain {
  font-size: var(--text-sm);
  line-height: 1.7;
  color: color-mix(in srgb, var(--color-contrast-ink) 72%, var(--color-contrast-surface));
  word-break: break-word;
}
.footer-links--plain .mono { color: var(--color-contrast-ink); }

.footer-base {
  border-top: var(--border-thin) solid var(--color-contrast-line);
  padding-block: var(--space-3) var(--space-6);
}
.footer-base__list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-4);
}
.footer-base__item {
  font-size: var(--text-sm);
  color: color-mix(in srgb, var(--color-contrast-ink) 70%, var(--color-contrast-surface));
}

/* ============================================================
   Responsive
   ============================================================ */
@media (max-width: 1024px) {
  .split { grid-template-columns: minmax(0, 1fr); gap: var(--space-4); }
  .toc { position: static; }
  .grid--3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .footer-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--space-4) var(--space-3); }
}

@media (max-width: 860px) {
  html { scroll-padding-top: 118px; }

  .nav-toggle { display: inline-flex; }

  .site-nav {
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    display: none;
    margin-inline-start: 0;
    padding: var(--space-2) var(--space-3) var(--space-4);
    background-color: var(--color-contrast-surface);
    border-top: var(--border-thin) solid var(--color-contrast-line);
    max-height: 70vh;
    overflow-y: auto;
  }
  .site-nav[data-open] { display: block; }
  .site-nav__list { flex-direction: column; align-items: stretch; gap: 0; }
  .site-nav__link {
    padding: 14px 8px;
    color: var(--color-contrast-ink);
    border-bottom: var(--border-thin) solid var(--color-contrast-line);
    border-radius: 0;
    font-size: var(--text-base);
  }
  .site-nav__link:hover {
    background-color: transparent;
    color: var(--color-contrast-accent);
  }
  .site-nav__link[aria-current="page"] {
    background-color: var(--color-contrast-accent);
    color: var(--color-contrast-surface);
    border-bottom-color: var(--color-contrast-accent);
  }

  .section,
  .section--lg { padding-block: var(--space-8); }
  .site-footer { margin-top: var(--space-8); }
}

@media (max-width: 640px) {
  .header-top__inner { gap: var(--space-2); }
  .brand-line { font-size: var(--text-xs); letter-spacing: 0.02em; }
  .header-actions { width: 100%; }
  .header-main__inner { min-height: 64px; }
  .brand__mono { display: none; }

  .grid--2,
  .grid--3 { grid-template-columns: minmax(0, 1fr); }
  .footer-grid { grid-template-columns: minmax(0, 1fr); gap: var(--space-4); padding-block: var(--space-6) var(--space-4); }
  .footer-tag { max-width: none; }
  .lede { font-size: var(--text-base); }
  .back-to-top { right: var(--space-2); bottom: var(--space-2); }
}

/* ============================================================
   Reduced motion
   ============================================================ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
  html.js [data-reveal] {
    opacity: 1 !important;
    transform: none !important;
  }
}