:root {
  --color-surface: #f8f7f7;
  --color-surface-alt: #eeeded;
  --color-surface-deep: #e1dfdf;
  --color-ink: #35302c;
  --color-ink-soft: #665d57;
  --color-ink-muted: #80766f;
  --color-line: #d5d3d2;
  --color-primary: #c1560b;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #f0e0d6;
  --color-accent: #1e7cb3;
  --color-accent-ink: #ffffff;
  --color-highlight: #d1e1eb;
  --color-focus: #1275af;
  --color-contrast-surface: #1c120c;
  --color-contrast-ink: #e7e5e4;
  --color-contrast-line: #49403c;
  --color-contrast-accent: #2597da;
  --overlay-scrim: linear-gradient(180deg, rgba(28, 18, 12, 0.35) 0%, rgba(28, 18, 12, 0.72) 55%, rgba(28, 18, 12, 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: 13.1px;
  --text-base: 16px;
  --text-lg: 24.0px;
  --text-xl: 36.0px;
  --text-2xl: 54.0px;
  --text-3xl: 81.0px;
  --text-4xl: 121.5px;
  --text-display: clamp(51px, 10.5vw, 134px);
  --text-figure: clamp(42px, 7.5vw, 96px);
  --weight-heading: 864;
  --weight-body: 400;
  --leading-body: 1.6;
  --leading-heading: 1.17;
  --tracking-heading: -0.014em;
  --radius-sm: 3px;
  --radius-md: 5px;
  --radius-lg: 7px;
  --radius-pill: 7px;
  --border-thin: 2px;
  --border-thick: 3px;
  --shadow-1: 4px 4px 0 #35302c;
  --shadow-2: 8px 8px 0 #35302c;
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1260px;
  --measure: 69ch;
  --gutter: 24px;
  --section-y: 91px;
  --section-y-lg: 127px;
}

/* ============================================================
   1. Reset 与中文排版基线
   ============================================================ */
*,
*::before,
*::after { box-sizing: border-box; }

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

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

img, svg, video { display: block; max-width: 100%; }
[hidden] { display: none !important; }

h1, h2, h3, h4, h5, h6 {
  margin: 0 0 var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  text-wrap: balance;
}
h1 { font-size: var(--text-2xl); }
h2 { font-size: var(--text-xl); }
h3 { font-size: var(--text-lg); }
h4, h5, h6 { font-size: var(--text-base); }

p { margin: 0 0 var(--space-2); max-width: var(--measure); }
ul, ol { margin: 0 0 var(--space-2); padding-left: 1.15em; }
strong, b { font-weight: var(--weight-heading); }
small { font-size: var(--text-sm); }
code, kbd, samp { font-family: var(--font-mono); font-size: var(--text-sm); }

a {
  color: var(--color-accent);
  text-decoration: underline;
  text-decoration-thickness: var(--border-thin);
  text-underline-offset: 3px;
  transition: color 140ms linear, text-decoration-color 140ms linear;
}
a:hover { color: var(--color-primary); text-decoration-color: var(--color-primary); }

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

:focus-visible {
  outline: var(--border-thick) solid var(--color-focus);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

.mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0;
}
.skew-fix { display: inline-block; transform: skewX(10deg); }
.visually-hidden {
  position: absolute; width: 1px; height: 1px; overflow: hidden;
  clip-path: inset(50%); white-space: nowrap;
}

/* ============================================================
   2. 布局骨架
   ============================================================ */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--space-3);
}
.grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid--4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.span-3 { grid-column: span 3; }
.span-4 { grid-column: span 4; }
.span-6 { grid-column: span 6; }
.span-8 { grid-column: span 8; }
.span-12 { grid-column: span 12; }

.split {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
  gap: var(--space-6);
  align-items: start;
}

.bleed-right { margin-right: calc(var(--gutter) * -1); }

.offset-grid { display: grid; gap: var(--space-3); }
.offset-grid > *:nth-child(even) { transform: translateY(var(--space-4)); }

.flow > * + * { margin-top: var(--space-2); }

/* 章节与分区 */
.section { padding-block: var(--section-y); }
.section--lg { padding-block: var(--section-y-lg); }
.section--tight { padding-block: calc(var(--section-y) / 2); }
.section--alt { background: var(--color-surface-alt); }
.section--deep { background: var(--color-surface-deep); }
.section--dark {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.section--dark h1,
.section--dark h2,
.section--dark h3,
.section--dark h4 { color: var(--color-contrast-ink); }
.section--dark p { color: color-mix(in srgb, var(--color-contrast-ink) 82%, transparent); }
.section--dark a { color: var(--color-contrast-accent); }
.section--dark a:hover { color: var(--color-contrast-ink); }
.section--primary { background: var(--color-primary); color: var(--color-primary-ink); }
.section--primary h1,
.section--primary h2,
.section--primary h3 { color: var(--color-primary-ink); }
.section--primary a { color: var(--color-primary-ink); }
.section--accent { background: var(--color-accent); color: var(--color-accent-ink); }
.section--accent h1,
.section--accent h2,
.section--accent h3 { color: var(--color-accent-ink); }

.slant-top {
  clip-path: polygon(0 44px, 100% 0, 100% 100%, 0 100%);
  padding-top: calc(var(--section-y) + 44px);
}
.slant-bottom {
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 44px), 0 100%);
  padding-bottom: calc(var(--section-y) + 44px);
}

/* 章节起手式 */
.section-head {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 30ch);
  gap: var(--space-3);
  align-items: end;
  margin-bottom: var(--space-4);
  padding-bottom: var(--space-2);
  border-bottom: var(--border-thick) solid var(--color-line);
}
.section--dark .section-head { border-bottom-color: var(--color-contrast-line); }
.section-title { margin: 0; font-size: var(--text-xl); }
.section-note {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  max-width: none;
}
.section--dark .section-note { color: color-mix(in srgb, var(--color-contrast-ink) 66%, transparent); }

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  margin: 0 0 var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-primary);
}
.eyebrow::before {
  content: "";
  width: 28px;
  height: 6px;
  background: var(--color-primary);
  transform: skewX(-20deg);
}
.section--dark .eyebrow { color: var(--color-contrast-accent); }
.section--dark .eyebrow::before { background: var(--color-contrast-accent); }

.display-title {
  margin: 0;
  font-family: var(--font-heading);
  font-size: var(--text-display);
  font-weight: var(--weight-heading);
  line-height: 0.92;
  letter-spacing: -0.03em;
}

.rule-offset {
  position: relative;
  height: 0;
  margin: var(--space-6) 0;
  border: 0;
  border-top: var(--border-thick) solid var(--color-ink);
}
.rule-offset::after {
  content: "";
  position: absolute;
  left: 12%;
  right: 0;
  top: 8px;
  border-top: var(--border-thin) solid var(--color-primary);
}

/* ============================================================
   3. 文本强调与基础组件
   ============================================================ */
.link-underline {
  color: inherit;
  text-decoration: none;
  padding-bottom: 3px;
  background-image: linear-gradient(var(--color-primary), var(--color-primary));
  background-repeat: no-repeat;
  background-position: 0 100%;
  background-size: 22% var(--border-thin);
  transition: background-size 150ms linear, color 150ms linear;
}
.link-underline:hover,
.link-underline:focus-visible { color: var(--color-primary); background-size: 100% var(--border-thin); }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  min-height: 44px;
  padding: 10px var(--space-3);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  letter-spacing: var(--tracking-heading);
  line-height: 1.2;
  text-align: center;
  text-decoration: none;
  color: var(--color-ink);
  background: var(--color-surface);
  border: var(--border-thin) solid var(--color-ink);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-1);
  cursor: pointer;
  transition: background-color 150ms linear, color 150ms linear,
    border-color 150ms linear, box-shadow 150ms linear, transform 150ms ease-out;
}
.btn:hover,
.btn:focus-visible {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-surface);
  transform: translate(3px, 3px);
  box-shadow: 2px 2px 0 var(--color-ink);
}
.btn--primary {
  background: var(--color-primary);
  color: var(--color-primary-ink);
  border-color: var(--color-primary);
}
.btn--primary:hover,
.btn--primary:focus-visible {
  background: var(--color-contrast-surface);
  border-color: var(--color-contrast-surface);
  color: var(--color-contrast-accent);
}
.btn--accent {
  background: var(--color-accent);
  color: var(--color-accent-ink);
  border-color: var(--color-accent);
}
.btn--ghost {
  background: transparent;
  box-shadow: none;
  border-color: var(--color-line);
}
.btn--sm { min-height: 38px; padding: 7px var(--space-2); }

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 8px;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  line-height: 1.3;
  border-radius: var(--radius-sm);
  border: var(--border-thin) solid transparent;
  background: var(--color-primary-soft);
  color: var(--color-primary);
}
.tag--accent { background: var(--color-highlight); color: var(--color-accent); }
.tag--dark {
  background: color-mix(in srgb, var(--color-contrast-accent) 18%, transparent);
  color: var(--color-contrast-accent);
}

.note {
  padding: var(--space-2) var(--space-3);
  background: var(--color-highlight);
  border-left: var(--border-thick) solid var(--color-accent);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}
.note p { font-size: var(--text-sm); }

.card {
  padding: var(--space-3);
  background: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-1);
  transition: border-color 140ms linear, box-shadow 140ms linear, transform 140ms ease-out;
}
.card:hover {
  border-color: var(--color-primary);
  transform: translate(-2px, -2px);
  box-shadow: var(--shadow-2);
}
.card__title {
  margin: 0 0 var(--space-1);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  line-height: var(--leading-heading);
}
.card__meta {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}
.card--flat { box-shadow: none; }
.card--dark {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-line);
  box-shadow: 6px 6px 0 color-mix(in srgb, var(--color-contrast-accent) 42%, transparent);
}
.card--dark:hover { border-color: var(--color-contrast-accent); }
.card--dark .card__title { color: var(--color-contrast-ink); }
.card--dark .card__meta { color: color-mix(in srgb, var(--color-contrast-ink) 62%, transparent); }

.panel {
  padding: var(--space-3);
  background: var(--color-surface-deep);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-md);
}
.panel--dark {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-line);
}

.stat { display: flex; flex-direction: column; gap: 8px; }
.stat__value {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: var(--text-xl);
  font-weight: var(--weight-heading);
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--color-ink);
}
.stat--hero .stat__value { font-size: var(--text-figure); }
.stat__label {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.12em;
  color: var(--color-ink-muted);
}
.stat--neon .stat__value {
  color: var(--color-contrast-accent);
  text-shadow: 0 0 14px color-mix(in srgb, var(--color-contrast-accent) 55%, transparent);
}
.stat--neon .stat__label { color: color-mix(in srgb, var(--color-contrast-ink) 64%, transparent); }

.table-scroll {
  overflow-x: auto;
  background: var(--color-surface-deep);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-md);
}
.data-table {
  width: 100%;
  min-width: 560px;
  border-collapse: collapse;
  font-size: var(--text-sm);
}
.data-table th,
.data-table td {
  padding: 10px var(--space-2);
  text-align: left;
  border-bottom: var(--border-thin) solid var(--color-line);
}
.data-table thead th {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  border-bottom-color: var(--color-contrast-line);
}
.data-table tbody tr { transition: background-color 130ms linear; }
.data-table tbody tr:hover { background: var(--color-highlight); }
.data-table td.mono, .data-table th.mono { font-family: var(--font-mono); }

.figure { margin: 0; }
.figure__frame {
  position: relative;
  overflow: hidden;
  aspect-ratio: 16 / 9;
  background: var(--color-surface-deep);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
}
.figure__frame img { width: 100%; height: 100%; object-fit: cover; }
.figure__frame--tall { aspect-ratio: 3 / 4; }
.figure__frame--wide { aspect-ratio: 21 / 9; }
.figure__frame--square { aspect-ratio: 1 / 1; }
.figure__frame--slant {
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 26px), 0 100%);
  border-radius: var(--radius-lg);
}
.figure__scrim { position: absolute; inset: 0; background: var(--overlay-scrim); }
.figure__caption {
  margin-top: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  max-width: none;
}
.figure__caption--overlay {
  position: absolute;
  left: var(--space-2);
  right: var(--space-2);
  bottom: var(--space-2);
  margin: 0;
  color: var(--color-contrast-ink);
}

.qa-item { border-bottom: var(--border-thin) solid var(--color-line); }
.qa-item summary {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  padding: var(--space-2) 0;
  cursor: pointer;
  list-style: none;
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  transition: color 140ms linear;
}
.qa-item summary::-webkit-details-marker { display: none; }
.qa-item summary::before {
  content: "Q";
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-primary);
}
.qa-item summary:hover { color: var(--color-primary); }
.qa-item[open] summary { color: var(--color-primary); }
.qa-item__body { padding-bottom: var(--space-3); color: var(--color-ink-soft); }
.section--dark .qa-item { border-bottom-color: var(--color-contrast-line); }
.section--dark .qa-item summary::before { color: var(--color-contrast-accent); }
.section--dark .qa-item__body { color: color-mix(in srgb, var(--color-contrast-ink) 78%, transparent); }

.steps { display: flex; flex-direction: column; }
.step {
  position: relative;
  padding: var(--space-3) 0 var(--space-3) var(--space-4);
  border-bottom: var(--border-thin) solid var(--color-line);
}
.step::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: var(--border-thick);
  background: var(--color-line);
  transition: background-color 150ms linear;
}
.step:hover::before { background: var(--color-primary); }
.step__idx {
  display: inline-block;
  margin-bottom: var(--space-1);
  padding: 2px 9px;
  background: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  transform: skewX(-12deg);
}

.chip-row { display: flex; flex-wrap: wrap; gap: var(--space-1); }
.chip {
  appearance: none;
  min-height: 44px;
  padding: 10px var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink-soft);
  background: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-pill);
  cursor: pointer;
  transition: background-color 140ms linear, color 140ms linear, border-color 140ms linear;
}
.chip:hover { color: var(--color-accent); border-color: var(--color-accent); }
.chip[aria-pressed="true"] {
  background: var(--color-highlight);
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.breadcrumb {
  background: var(--color-surface-alt);
  border-bottom: var(--border-thin) solid var(--color-line);
}
.breadcrumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1);
  max-width: var(--container);
  margin: 0 auto;
  padding: var(--space-2) var(--gutter);
  list-style: none;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
}
.breadcrumb__item { display: flex; align-items: center; gap: var(--space-1); }
.breadcrumb__item + .breadcrumb__item::before { content: "/"; color: var(--color-line); }
.breadcrumb__link { color: var(--color-ink-soft); text-decoration: none; }
.breadcrumb__link:hover { color: var(--color-primary); }
.breadcrumb__current { color: var(--color-primary); font-weight: var(--weight-heading); }

/* ============================================================
   4. 头部
   ============================================================ */
.skip-link {
  position: fixed;
  top: var(--space-1);
  left: var(--space-1);
  z-index: 200;
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding: 0 var(--space-3);
  transform: translateY(-220%);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  letter-spacing: var(--tracking-heading);
  text-decoration: none;
  border: var(--border-thin) solid var(--color-contrast-accent);
  border-radius: var(--radius-sm);
  transition: transform 140ms linear;
}
.skip-link:focus { transform: translateY(0); }

.site-header {
  position: sticky;
  top: 0;
  z-index: 90;
  background: var(--color-surface);
}

.status-strip {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
}
.status-strip__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1) var(--space-3);
  max-width: var(--container);
  margin-inline: auto;
  padding: 7px var(--gutter);
  font-size: var(--text-sm);
}
.status-strip__item { display: inline-flex; align-items: center; gap: 6px; white-space: nowrap; }
.status-strip__key {
  color: color-mix(in srgb, var(--color-contrast-ink) 60%, transparent);
  letter-spacing: 0.14em;
}
.status-strip__val { color: var(--color-contrast-accent); font-weight: var(--weight-heading); }
.status-strip__item--tail {
  margin-left: auto;
  color: color-mix(in srgb, var(--color-contrast-ink) 74%, transparent);
}
.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--color-contrast-accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--color-contrast-accent) 26%, transparent);
  animation: statusPulse 2400ms linear infinite;
}
@keyframes statusPulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.42; }
}

.header-bar {
  position: relative;
  background: var(--color-surface);
  border-bottom: var(--border-thick) solid var(--color-ink);
}
.header-bar__inner {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  max-width: var(--container);
  margin-inline: auto;
  padding: var(--space-2) var(--gutter);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  flex: 0 0 auto;
  color: var(--color-ink);
  text-decoration: none;
}
.brand__mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 54px;
  height: 44px;
  padding: 0 10px;
  background: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-mono);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  border-radius: var(--radius-sm);
  transform: skewX(-10deg);
  box-shadow: var(--shadow-1);
  transition: background-color 150ms linear, transform 150ms linear;
}
.brand:hover .brand__mark { background: var(--color-accent); transform: skewX(-10deg) translate(-2px, -2px); }
.brand__text { display: flex; flex-direction: column; gap: 4px; }
.brand__name {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  line-height: 1;
}
.brand__sub {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  line-height: 1;
  color: var(--color-ink-muted);
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-1);
  min-height: 44px;
  padding: 0 var(--space-2);
  color: var(--color-ink);
  background: var(--color-surface);
  border: var(--border-thin) solid var(--color-ink);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-1);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  cursor: pointer;
  transition: background-color 140ms linear, color 140ms linear, border-color 140ms linear;
}
.nav-toggle:hover { background: var(--color-contrast-surface); color: var(--color-contrast-ink); border-color: var(--color-contrast-surface); }
.nav-toggle__bars { display: inline-flex; flex-direction: column; gap: 4px; width: 18px; }
.nav-toggle__bars i {
  display: block;
  height: var(--border-thin);
  background: currentColor;
  transition: transform 150ms linear, opacity 150ms linear;
}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars i:nth-child(1) { transform: translateY(6px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle__bars i:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] .nav-toggle__bars i:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }

.site-nav { display: flex; align-items: center; gap: var(--space-2); margin-left: auto; }
.site-nav__list {
  display: flex;
  align-items: center;
  gap: 2px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.site-nav__link {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  min-height: 44px;
  padding: 8px 12px;
  color: var(--color-ink);
  text-decoration: none;
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  transition: color 140ms linear;
}
.site-nav__link::before {
  content: "";
  flex: 0 0 auto;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--color-contrast-accent);
  opacity: 0;
  transform: scale(0.4);
  transition: opacity 140ms linear, transform 140ms linear;
}
.site-nav__link::after {
  content: "";
  position: absolute;
  left: 10px;
  right: 10px;
  bottom: 4px;
  height: 5px;
  background: var(--color-primary);
  transform: skewX(-20deg) scaleX(0);
  transform-origin: left center;
  transition: transform 160ms linear;
}
.site-nav__idx {
  font-size: var(--text-xs);
  letter-spacing: 0;
  color: var(--color-ink-muted);
  transition: color 140ms linear;
}
.site-nav__link:hover { color: var(--color-primary); }
.site-nav__link:hover::after { transform: skewX(-20deg) scaleX(1); }
.site-nav__link[aria-current="page"] { color: var(--color-primary); }
.site-nav__link[aria-current="page"]::before {
  opacity: 1;
  transform: none;
  box-shadow: 0 0 9px color-mix(in srgb, var(--color-contrast-accent) 70%, transparent);
}
.site-nav__link[aria-current="page"]::after { transform: skewX(-20deg) scaleX(1); }
.site-nav__link[aria-current="page"] .site-nav__idx { color: var(--color-primary); }
.site-nav__cta { display: flex; align-items: center; }

.scroll-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: calc(var(--border-thick) * -1);
  height: var(--border-thick);
  background: transparent;
  pointer-events: none;
}
.scroll-progress__bar {
  display: block;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 120ms linear;
}

/* ============================================================
   5. 页脚
   ============================================================ */
.site-footer {
  position: relative;
  margin-top: var(--section-y);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.footer-slant {
  height: 12px;
  background: linear-gradient(
    90deg,
    var(--color-primary) 0 34%,
    var(--color-surface-alt) 34% 39%,
    var(--color-accent) 39% 100%
  );
  clip-path: polygon(0 0, 100% 0, 100% 44%, 0 100%);
}
.site-footer__inner {
  display: grid;
  grid-template-columns: 1.4fr 1fr 0.8fr 1.3fr 1.3fr;
  gap: var(--space-6) var(--space-4);
  max-width: var(--container);
  margin-inline: auto;
  padding: var(--space-8) var(--gutter) var(--space-6);
}
.footer-cols { display: contents; }

.footer-brand__mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 7px 12px;
  background: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-mono);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  border-radius: var(--radius-sm);
  transform: skewX(-10deg);
  box-shadow: 6px 6px 0 color-mix(in srgb, var(--color-contrast-accent) 55%, transparent);
}
.footer-brand__name {
  margin: var(--space-2) 0 4px;
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-contrast-ink);
}
.footer-brand__tag {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: color-mix(in srgb, var(--color-contrast-ink) 70%, transparent);
}
.footer-col__title {
  margin: 0 0 var(--space-2);
  padding-bottom: var(--space-1);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: var(--weight-heading);
  letter-spacing: 0.16em;
  color: var(--color-contrast-accent);
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
}
.footer-list {
  display: flex;
  flex-direction: column;
  gap: 2px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.footer-link {
  display: inline-flex;
  align-items: center;
  min-height: 34px;
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  text-decoration: none;
  background-image: linear-gradient(var(--color-contrast-accent), var(--color-contrast-accent));
  background-repeat: no-repeat;
  background-position: 0 100%;
  background-size: 14% var(--border-thin);
  transition: background-size 150ms linear, color 150ms linear;
}
.footer-link:hover,
.footer-link:focus-visible {
  color: var(--color-contrast-accent);
  background-size: 100% var(--border-thin);
}
.footer-contact {
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-style: normal;
  font-size: var(--text-sm);
  color: var(--color-contrast-ink);
}
.footer-contact__line { display: block; }
.footer-contact__note,
.footer-scope {
  margin: var(--space-2) 0 0;
  font-size: var(--text-sm);
  color: color-mix(in srgb, var(--color-contrast-ink) 66%, transparent);
}
.footer-meta {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  margin: 0;
  padding: 0;
  list-style: none;
}
.footer-meta__item {
  display: flex;
  flex-direction: column;
  gap: 2px;
  padding-bottom: var(--space-1);
  font-size: var(--text-sm);
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
}
.footer-meta__key {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  color: color-mix(in srgb, var(--color-contrast-ink) 58%, transparent);
}
.to-top {
  margin-top: var(--space-3);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 10px var(--space-3);
  color: var(--color-contrast-ink);
  background: transparent;
  border: var(--border-thin) solid var(--color-contrast-accent);
  border-radius: var(--radius-sm);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  cursor: pointer;
  transition: background-color 140ms linear, color 140ms linear;
}
.to-top:hover { background: var(--color-contrast-accent); color: var(--color-contrast-surface); }

.footer-bottom { border-top: var(--border-thin) solid var(--color-contrast-line); }
.footer-bottom__inner {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: var(--space-1) var(--space-3);
  max-width: var(--container);
  margin-inline: auto;
  padding: var(--space-3) var(--gutter);
}
.footer-legal {
  margin: 0;
  max-width: none;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-contrast-ink);
}
.footer-legal--muted { color: color-mix(in srgb, var(--color-contrast-ink) 60%, transparent); }

/* ============================================================
   6. 响应式
   ============================================================ */
@media (max-width: 1180px) {
  .site-nav__link { padding: 8px 9px; }
  .brand__sub { display: none; }
}

@media (max-width: 1080px) {
  .site-footer__inner { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 900px) {
  .header-bar__inner { flex-wrap: wrap; gap: var(--space-2); }
  .nav-toggle { display: inline-flex; margin-left: auto; }
  .brand__sub { display: inline-block; }

  .site-nav {
    order: 3;
    flex: 1 0 100%;
    display: block;
    margin-left: 0;
    padding: 0;
    background: var(--color-surface-alt);
    border-top: var(--border-thin) solid var(--color-line);
    overflow-x: auto;
    overflow-y: hidden;
  }
  .site-nav__list {
    flex-direction: row;
    flex-wrap: nowrap;
    width: max-content;
    padding: 0 var(--space-2);
  }
  .site-nav__list > li { flex: 0 0 auto; }
  .site-nav__list > li:nth-child(n + 5) { display: none; }
  .site-nav__link {
    padding: 12px var(--space-2);
    white-space: nowrap;
  }
  .site-nav__link::after { left: 12px; right: 12px; bottom: 6px; }
  .site-nav__cta { display: none; }

  .site-nav[data-open] {
    max-height: 70vh;
    overflow-y: auto;
    background: var(--color-contrast-surface);
    border-top: var(--border-thick) solid var(--color-primary);
    box-shadow: var(--shadow-2);
  }
  .site-nav[data-open] .site-nav__list {
    flex-direction: column;
    width: 100%;
    padding: var(--space-1) 0;
  }
  .site-nav[data-open] .site-nav__list > li {
    display: block;
    width: 100%;
    border-bottom: var(--border-thin) solid var(--color-contrast-line);
  }
  .site-nav[data-open] .site-nav__list > li:nth-child(n + 5) { display: block; }
  .site-nav[data-open] .site-nav__link {
    width: 100%;
    padding: var(--space-2) var(--space-3);
    color: var(--color-contrast-ink);
  }
  .site-nav[data-open] .site-nav__link:hover { color: var(--color-contrast-accent); }
  .site-nav[data-open] .site-nav__link::after {
    left: var(--space-3);
    right: auto;
    width: 26px;
    bottom: 12px;
  }
  .site-nav[data-open] .site-nav__idx { color: var(--color-contrast-accent); }
  .site-nav[data-open] .site-nav__link[aria-current="page"] {
    color: var(--color-contrast-accent);
    background: color-mix(in srgb, var(--color-contrast-accent) 14%, transparent);
  }
  .site-nav[data-open] .site-nav__link[aria-current="page"]::after {
    transform: skewX(-20deg) scaleX(1);
  }
  .site-nav[data-open] .site-nav__cta {
    display: block;
    padding: var(--space-2) var(--space-3) var(--space-3);
  }
  .site-nav[data-open] .site-nav__cta .btn { width: 100%; min-height: 44px; }
  .footer-link { min-height: 44px; }

  .section { padding-block: calc(var(--section-y) * 0.66); }
  .section--lg { padding-block: calc(var(--section-y-lg) * 0.66); }
  .slant-top {
    clip-path: polygon(0 24px, 100% 0, 100% 100%, 0 100%);
    padding-top: calc(var(--section-y) * 0.66 + 24px);
  }
  .slant-bottom {
    clip-path: polygon(0 0, 100% 0, 100% calc(100% - 24px), 0 100%);
    padding-bottom: calc(var(--section-y) * 0.66 + 24px);
  }

  .grid--3,
  .grid--4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .span-3,
  .span-4 { grid-column: span 6; }
  .span-8 { grid-column: span 12; }
  .split { grid-template-columns: minmax(0, 1fr); gap: var(--space-4); }
  .section-head { grid-template-columns: minmax(0, 1fr); align-items: start; }
  .offset-grid > *:nth-child(even) { transform: none; }
}

@media (max-width: 620px) {
  .grid,
  .grid--2,
  .grid--3,
  .grid--4 { grid-template-columns: minmax(0, 1fr); }
  .span-3,
  .span-4,
  .span-6,
  .span-8,
  .span-12 { grid-column: span 1; }
  .site-footer__inner {
    grid-template-columns: minmax(0, 1fr);
    padding-top: var(--space-6);
    gap: var(--space-4);
  }
  .footer-slant { height: 8px; }
  .status-strip__item--tail { margin-left: 0; }
  h1 { font-size: var(--text-xl); }
  h2 { font-size: var(--text-lg); }
  .stat__value { font-size: var(--text-lg); }
  .bleed-right { margin-right: 0; }
}

/* ============================================================
   7. 动效降级
   ============================================================ */
@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;
  }
  .status-dot { animation: none; box-shadow: none; }
  .scroll-progress__bar { transition: none; }
}