/* ============================================================
   qiuyi-arena.com.cn — 共享 Site Kit
   口径编号体系 T / V / G / N · 白皮书式静态站点
   ============================================================ */

/* ---------- 1. reset ---------- */
*,
*::before,
*::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body,
h1, h2, h3, h4, h5, h6,
p, ul, ol, li, figure, figcaption,
blockquote, dl, dt, dd, table, th, td, fieldset, legend {
  margin: 0;
  padding: 0;
}

ul, ol { list-style: none; }

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

button, input, select, textarea {
  font: inherit;
  color: inherit;
}

button {
  background: none;
  border: 0;
  cursor: pointer;
}

a { color: inherit; text-decoration: none; }

table { border-collapse: collapse; }

/* ---------- 2. tokens ---------- */
:root {
  --c-ink: #0B0E11;
  --c-silver: #C7CDD4;
  --c-graphite: #171C21;
  --c-paper: #F2F4F5;
  --c-cyan: #2FF0C8;
  --c-cyan-deep: #0E9C80;
  --c-orange: #FF6B2C;
  --c-violet-a: #2E3A8C;
  --c-violet-b: #7C5CFF;
  --c-scale: #6E7A82;
  --c-ice: #DCE8EE;
  --c-space: #0E1B2B;

  --line-soft: rgba(199, 205, 212, 0.16);
  --line-mid: rgba(199, 205, 212, 0.28);
  --line-strong: rgba(199, 205, 212, 0.45);
  --line-cyan: rgba(47, 240, 200, 0.32);

  --font-head: "Source Han Sans SC", "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  --font-body: "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  --font-mono: "JetBrains Mono", "DIN Alternate", "DIN Condensed", "SFMono-Regular", "Menlo", "Consolas", "Liberation Mono", monospace;

  --wrap-max: 1200px;
  --gutter: clamp(18px, 4vw, 48px);
  --radius: 2px;

  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

/* ---------- 3. base type ---------- */
body {
  background-color: var(--c-ink);
  color: var(--c-paper);
  font-family: var(--font-body);
  font-size: 15px;
  line-height: 1.75;
  letter-spacing: 0.01em;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-head);
  font-weight: 500;
  letter-spacing: 0.02em;
  line-height: 1.3;
  color: var(--c-paper);
}

h1 { font-size: clamp(30px, 4.4vw, 44px); line-height: 1.22; }
h2 { font-size: clamp(22px, 2.6vw, 30px); line-height: 1.35; }
h3 { font-size: clamp(17px, 1.5vw, 20px); line-height: 1.5; }

p { line-height: 1.75; }

strong, b { font-weight: 600; }

small { font-size: 12.5px; }

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

.num { color: var(--c-cyan); }

/* ---------- 4. focus / selection / skip ---------- */
:focus-visible {
  outline: 2px solid var(--c-cyan);
  outline-offset: 3px;
  border-radius: 1px;
}

::selection {
  background: var(--c-cyan);
  color: var(--c-ink);
}

.skip-link {
  position: absolute;
  top: -80px;
  left: var(--gutter);
  z-index: 120;
  padding: 10px 16px;
  background: var(--c-cyan);
  color: var(--c-ink);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.12em;
  transition: top 0.18s var(--ease);
}

.skip-link:focus {
  top: 12px;
}

/* ---------- 5. layout ---------- */
.wrap {
  width: 100%;
  max-width: var(--wrap-max);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.section {
  padding-block: clamp(36px, 5.5vw, 82px);
}

.section--tight { padding-block: clamp(22px, 3vw, 42px); }
.section--flush { padding-block: 0; }

.section-head {
  display: grid;
  gap: 10px;
  margin-bottom: clamp(20px, 3vw, 36px);
  padding-bottom: 14px;
  border-bottom: 1px solid var(--line-mid);
}

.section-title {
  font-family: var(--font-head);
  font-size: clamp(22px, 2.6vw, 30px);
  line-height: 1.35;
  margin: 0;
}

.eyebrow {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--c-cyan);
}

.section-note {
  font-size: 13.5px;
  color: var(--c-scale);
  max-width: 62ch;
}

.grid {
  display: grid;
  gap: clamp(14px, 1.8vw, 26px);
  grid-template-columns: 1fr;
}

.grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }

.split {
  display: grid;
  gap: clamp(18px, 2.4vw, 34px);
  grid-template-columns: 1fr;
}

.prose {
  max-width: 68ch;
  font-size: 15.5px;
  line-height: 1.78;
  color: var(--c-paper);
}

.prose p + p { margin-top: 1em; }
.prose h2 { margin-top: 1.6em; margin-bottom: 0.5em; }
.prose h3 { margin-top: 1.4em; margin-bottom: 0.4em; }
.prose ul, .prose ol { margin-top: 0.8em; padding-left: 1.2em; }
.prose ul li { list-style: none; position: relative; }
.prose ul li::before {
  content: "";
  position: absolute;
  left: -1.1em;
  top: 0.78em;
  width: 6px;
  height: 1px;
  background: var(--c-cyan);
}

.surface-paper {
  background: var(--c-paper);
  color: var(--c-ink);
}

.surface-paper h1, .surface-paper h2, .surface-paper h3 { color: var(--c-ink); }
.surface-paper .eyebrow { color: var(--c-cyan-deep); }
.surface-paper .section-head { border-bottom-color: var(--c-ice); }
.surface-paper .prose { color: #1A2026; }

.surface-space {
  background: var(--c-space);
  color: var(--c-silver);
}

.surface-graphite {
  background: var(--c-graphite);
  color: var(--c-silver);
}

/* ---------- 6. buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 11px 17px;
  border: 1px solid currentColor;
  border-radius: var(--radius);
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1;
  letter-spacing: 0.12em;
  white-space: nowrap;
  transition: background-color 0.2s var(--ease), color 0.2s var(--ease), border-color 0.2s var(--ease);
}

.btn-primary {
  background: var(--c-cyan);
  border-color: var(--c-cyan);
  color: var(--c-ink);
}

.btn-primary:hover {
  background: transparent;
  color: var(--c-cyan);
}

.btn-ghost {
  color: var(--c-silver);
  border-color: var(--line-mid);
}

.btn-ghost:hover {
  color: var(--c-cyan);
  border-color: var(--c-cyan);
}

.btn-violet {
  background-image: linear-gradient(120deg, var(--c-violet-a), var(--c-violet-b));
  border-color: transparent;
  color: var(--c-paper);
}

.btn-violet:hover {
  color: var(--c-paper);
  filter: brightness(1.12);
}

/* ---------- 7. tags ---------- */
.tag {
  display: inline-block;
  padding: 3px 8px;
  border: 1px solid var(--line-mid);
  border-radius: var(--radius);
  font-family: var(--font-mono);
  font-size: 11px;
  line-height: 1.6;
  letter-spacing: 0.1em;
  color: var(--c-silver);
}

.tag--cyan {
  color: var(--c-cyan);
  border-color: var(--line-cyan);
  background: rgba(47, 240, 200, 0.07);
}

.tag--orange {
  color: var(--c-orange);
  border-color: rgba(255, 107, 44, 0.4);
  background: rgba(255, 107, 44, 0.08);
}

.tag--violet {
  color: var(--c-paper);
  border-color: transparent;
  background-image: linear-gradient(120deg, var(--c-violet-a), var(--c-violet-b));
}

/* ---------- 8. panel / metric / ledger ---------- */
.panel {
  position: relative;
  padding: clamp(16px, 2vw, 26px);
  background: var(--c-graphite);
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
}

.panel-label {
  display: inline-block;
  margin-bottom: 12px;
  padding: 3px 8px;
  background: var(--c-ink);
  border: 1px solid var(--line-mid);
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.16em;
  color: var(--c-scale);
}

.metric {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding-block: 12px;
}

.metric-value {
  font-family: var(--font-mono);
  font-weight: 600;
  font-size: clamp(38px, 6vw, 72px);
  line-height: 1;
  letter-spacing: -0.01em;
  color: var(--c-paper);
}

.metric-unit {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.1em;
  color: var(--c-cyan);
}

.metric-label {
  font-size: 13px;
  color: var(--c-scale);
}

.metric--cyan .metric-value { color: var(--c-cyan); }
.metric--violet .metric-value { color: var(--c-violet-b); }

.ledger {
  width: 100%;
  font-size: 14px;
  text-align: left;
}

.ledger caption {
  caption-side: top;
  padding-bottom: 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--c-scale);
  text-align: left;
}

.ledger th,
.ledger td {
  padding: 12px 14px;
  border-bottom: 1px solid var(--line-soft);
  vertical-align: top;
}

.ledger thead th {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.12em;
  color: var(--c-scale);
  border-bottom-color: var(--line-strong);
  white-space: nowrap;
}

.ledger tbody th {
  font-weight: 500;
  color: var(--c-paper);
}

.ledger td { color: var(--c-silver); }

/* ---------- 9. tick rail ---------- */
.tick-rail {
  display: flex;
  flex-direction: column;
  border-left: 1px solid var(--line-mid);
}

.tick {
  display: grid;
  grid-template-columns: 3.2em 1fr;
  gap: 12px;
  align-items: baseline;
  padding: 11px 12px;
  border-bottom: 1px solid var(--line-soft);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--c-scale);
  transition: color 0.18s var(--ease), background-color 0.18s var(--ease);
}

.tick:hover { color: var(--c-silver); }

.tick.is-active,
.tick[aria-current="true"] {
  color: var(--c-cyan);
  background: rgba(47, 240, 200, 0.06);
  border-bottom-color: var(--line-cyan);
}

.tick-code {
  font-weight: 600;
  color: inherit;
}

/* ---------- 10. callout ---------- */
.callout {
  padding: 14px 18px;
  border-left: 2px solid var(--c-cyan);
  background: rgba(47, 240, 200, 0.05);
  font-size: 14px;
  line-height: 1.72;
  color: var(--c-silver);
}

.callout-title {
  display: block;
  margin-bottom: 6px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--c-cyan);
}

.callout--warning {
  border-left-color: var(--c-orange);
  background: rgba(255, 107, 44, 0.07);
}

.callout--warning .callout-title { color: var(--c-orange); }

/* ---------- 11. tabs ---------- */
.tabs { margin-block: clamp(16px, 2.4vw, 30px); }

.tablist {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  border-bottom: 1px solid var(--line-mid);
}

.tab {
  margin-bottom: -1px;
  padding: 11px 14px;
  border-bottom: 2px solid transparent;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.1em;
  color: var(--c-scale);
  transition: color 0.18s var(--ease), border-color 0.18s var(--ease);
}

.tab:hover { color: var(--c-paper); }

.tab[aria-selected="true"] {
  color: var(--c-cyan);
  border-bottom-color: var(--c-cyan);
}

.tabpanel { padding-block: 22px 0; }
.tabpanel[hidden] { display: none; }

/* ---------- 12. toc / breadcrumb ---------- */
.toc {
  position: relative;
  padding-left: 15px;
  border-left: 1px solid var(--line-mid);
}

.toc-title {
  margin-bottom: 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--c-scale);
}

.toc-list {
  display: flex;
  flex-direction: column;
  gap: 1px;
}

.toc-link {
  display: block;
  margin-left: -16px;
  padding: 6px 0 6px 15px;
  border-left: 2px solid transparent;
  font-size: 13.5px;
  color: var(--c-silver);
  transition: color 0.18s var(--ease), border-color 0.18s var(--ease);
}

.toc-link:hover { color: var(--c-paper); }

.toc-link.is-active,
.toc-link[aria-current="true"] {
  color: var(--c-cyan);
  border-left-color: var(--c-cyan);
}

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  color: var(--c-scale);
}

.breadcrumb li {
  display: flex;
  align-items: center;
  gap: 8px;
}

.breadcrumb li::after {
  content: "/";
  color: var(--c-scale);
}

.breadcrumb li:last-child::after { content: none; }
.breadcrumb a { color: var(--c-silver); }
.breadcrumb a:hover { color: var(--c-cyan); }

/* ---------- 13. figure / image containers ---------- */
.figure {
  margin: 0;
  padding: 10px;
  background: var(--c-graphite);
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
}

.figure-frame {
  position: relative;
  overflow: hidden;
  aspect-ratio: 16 / 9;
  background-image: linear-gradient(180deg, rgba(199, 205, 212, 0.07), rgba(199, 205, 212, 0));
  background-color: var(--c-ink);
}

.figure-frame img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.figure-frame--wide { aspect-ratio: 21 / 9; }
.figure-frame--tall { aspect-ratio: 4 / 5; }
.figure-frame--square { aspect-ratio: 1 / 1; }

.figure-frame--empty::after {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    repeating-linear-gradient(90deg, rgba(199, 205, 212, 0.09) 0 1px, transparent 1px 28px),
    repeating-linear-gradient(0deg, rgba(199, 205, 212, 0.09) 0 1px, transparent 1px 28px);
  pointer-events: none;
}

.figure-caption {
  margin-top: 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  line-height: 1.65;
  letter-spacing: 0.06em;
  color: var(--c-scale);
}

.figure-grid {
  display: grid;
  gap: clamp(12px, 1.6vw, 20px);
  grid-template-columns: 1fr;
}

/* ---------- 14. motion helpers ---------- */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--c-cyan);
  z-index: 90;
  pointer-events: none;
}

html.js [data-reveal] {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity 0.55s var(--ease), transform 0.55s var(--ease);
}

html.js [data-reveal].is-visible {
  opacity: 1;
  transform: none;
}

/* ---------- 15. HEADER ---------- */
.site-header {
  position: relative;
  z-index: 60;
  background-color: var(--c-ink);
  border-bottom: 1px solid var(--line-mid);
}

.site-header::before {
  content: "";
  position: absolute;
  left: 0;
  bottom: -1px;
  width: 72px;
  height: 1px;
  background: var(--c-cyan);
}

.header-inner {
  display: flex;
  align-items: center;
  gap: clamp(10px, 1.6vw, 24px);
  padding-block: 14px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  flex: 0 0 auto;
  min-width: 0;
}

.brand-mark {
  flex: 0 0 auto;
  padding: 5px 6px;
  border: 1px solid rgba(47, 240, 200, 0.55);
  border-radius: var(--radius);
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 600;
  line-height: 1;
  letter-spacing: 0.14em;
  color: var(--c-cyan);
}

.brand-mark--lg {
  padding: 8px 9px;
  font-size: 14px;
}

.brand-text {
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.brand-name {
  font-family: var(--font-head);
  font-size: 15px;
  font-weight: 500;
  letter-spacing: 0.05em;
  color: var(--c-paper);
  white-space: nowrap;
}

.brand-domain {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.05em;
  color: var(--c-scale);
  white-space: nowrap;
}

.caliber-badge {
  flex: 0 0 auto;
  padding: 4px 7px;
  background: var(--c-cyan);
  border-radius: var(--radius);
  font-family: var(--font-mono);
  font-size: 11px;
  line-height: 1;
  letter-spacing: 0.08em;
  color: var(--c-ink);
  white-space: nowrap;
}

.header-rule {
  flex: 1 1 auto;
  min-width: 20px;
  height: 10px;
  background-image:
    repeating-linear-gradient(to right, rgba(199, 205, 212, 0.5) 0 1px, transparent 1px 9px),
    linear-gradient(var(--line-mid), var(--line-mid));
  background-repeat: no-repeat, no-repeat;
  background-size: 100% 10px, 100% 1px;
  background-position: 0 0, 0 50%;
}

.header-meta {
  display: none;
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--c-scale);
  white-space: nowrap;
}

.nav-toggle {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  flex: 0 0 auto;
  padding: 9px 12px;
  border: 1px solid var(--line-mid);
  border-radius: var(--radius);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--c-silver);
  transition: color 0.18s var(--ease), border-color 0.18s var(--ease), background-color 0.18s var(--ease);
}

.nav-toggle:hover {
  color: var(--c-cyan);
  border-color: var(--c-cyan);
}

.nav-toggle[aria-expanded="true"] {
  color: var(--c-cyan);
  border-color: var(--c-cyan);
  background: rgba(47, 240, 200, 0.07);
}

.nav-toggle-bar {
  position: relative;
  display: block;
  width: 14px;
  height: 1px;
  background: currentColor;
}

.nav-toggle-bar::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: 4px;
  height: 1px;
  background: currentColor;
}

.nav-toggle-label {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
}

.site-nav { display: none; }

/* ---------- 16. FOOTER ---------- */
.site-footer {
  margin-top: clamp(48px, 8vw, 110px);
  background-color: var(--c-space);
  color: var(--c-silver);
  border-top: 1px solid var(--line-cyan);
}

.footer-inner {
  padding-block: clamp(34px, 5vw, 64px) 26px;
}

.footer-head {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
  align-items: start;
  padding-bottom: clamp(22px, 3vw, 36px);
  border-bottom: 1px solid var(--line-soft);
}

.footer-brand {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
}

.footer-brand-name {
  font-family: var(--font-head);
  font-size: 19px;
  letter-spacing: 0.06em;
  color: var(--c-paper);
}

.footer-brand-note {
  width: 100%;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.06em;
  color: var(--c-scale);
}

.footer-cta { margin: 0; }

.footer-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(22px, 3vw, 40px);
  padding-block: clamp(24px, 3.4vw, 42px);
}

.footer-section { min-width: 0; }

.footer-title {
  margin-bottom: 14px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--line-soft);
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.18em;
  color: var(--c-cyan);
}

.footer-list {
  display: flex;
  flex-direction: column;
}

.footer-link {
  display: inline-block;
  padding: 6px 0;
  font-size: 14px;
  color: var(--c-silver);
  transition: color 0.18s var(--ease), transform 0.18s var(--ease);
}

.footer-link:hover {
  color: var(--c-cyan);
  transform: translateX(3px);
}

.footer-lines {
  display: flex;
  flex-direction: column;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 12.5px;
  line-height: 1.6;
  color: var(--c-silver);
  word-break: break-word;
}

.footer-note {
  margin-top: 14px;
  max-width: 38ch;
  font-size: 12.5px;
  line-height: 1.7;
  color: var(--c-scale);
}

.footer-base {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 8px 22px;
  padding-top: 18px;
  border-top: 1px solid var(--line-soft);
}

.footer-closing {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.08em;
  color: var(--c-cyan);
}

.footer-legal,
.footer-stamp {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.04em;
  color: var(--c-scale);
}

/* ---------- 17. responsive ---------- */
@media (min-width: 640px) {
  .grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .figure-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .footer-head { grid-template-columns: 1fr auto; align-items: end; }
  .footer-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (min-width: 720px) {
  .header-rule { display: block; }
}

@media (min-width: 1024px) {
  .grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .grid-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
  .figure-grid--three { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .footer-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }

  .split { grid-template-columns: minmax(200px, 3fr) minmax(0, 9fr); }
  .split--reverse { grid-template-columns: minmax(0, 9fr) minmax(200px, 3fr); }
  .split--even { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (min-width: 1080px) {
  .nav-toggle { display: none; }

  .site-nav {
    display: block;
    flex: 0 0 auto;
  }

  .nav-list {
    display: flex;
    align-items: center;
    gap: clamp(10px, 1.5vw, 24px);
  }

  .nav-link {
    display: inline-block;
    padding: 6px 0;
    border-bottom: 1px solid transparent;
    font-size: 13.5px;
    letter-spacing: 0.03em;
    color: var(--c-silver);
    white-space: nowrap;
    transition: color 0.18s var(--ease), border-color 0.18s var(--ease);
  }

  .nav-link:hover {
    color: var(--c-paper);
    border-bottom-color: rgba(47, 240, 200, 0.6);
  }

  .nav-link[aria-current="page"] {
    color: var(--c-cyan);
    border-bottom-color: var(--c-cyan);
  }
}

@media (min-width: 1300px) {
  .header-meta { display: block; }
}

@media (max-width: 1079.98px) {
  .site-nav {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--c-graphite);
    border-bottom: 1px solid var(--line-mid);
    box-shadow: 0 20px 44px rgba(0, 0, 0, 0.55);
  }

  .site-nav[data-open] { display: block; }

  .nav-list {
    display: flex;
    flex-direction: column;
    padding: 6px var(--gutter) 18px;
  }

  .nav-link {
    display: block;
    padding: 13px 0;
    border-bottom: 1px solid var(--line-soft);
    font-size: 15px;
    color: var(--c-silver);
  }

  .nav-link[aria-current="page"] { color: var(--c-cyan); }

  .nav-link[aria-current="page"]::before {
    content: "▍";
    margin-right: 6px;
    font-family: var(--font-mono);
    color: var(--c-cyan);
  }
}

@media (max-width: 719.98px) {
  .header-rule { display: none; }
  .header-meta { display: none; }
  .brand-domain { display: none; }
}

/* ---------- 18. 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;
    scroll-behavior: auto !important;
  }

  html.js [data-reveal] {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .skip-link { transition: none; }
  .footer-link:hover { transform: none; }
  .scroll-progress { transition: none; }
}