:root {
  --color-surface: #f7f8f7;
  --color-surface-alt: #eeefee;
  --color-surface-deep: #e1e3e2;
  --color-ink: #404944;
  --color-ink-soft: #636f68;
  --color-ink-muted: #79867f;
  --color-line: #d6d8d7;
  --color-primary: #6c7972;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #e4e6e4;
  --color-accent: #198547;
  --color-accent-ink: #ffffff;
  --color-highlight: #cfe3d7;
  --color-focus: #0f803f;
  --color-contrast-surface: #1c1f1d;
  --color-contrast-ink: #e4e7e5;
  --color-contrast-line: #484b49;
  --color-contrast-accent: #28d773;
  --overlay-scrim: linear-gradient(180deg, rgba(28, 31, 29, 0.35) 0%, rgba(28, 31, 29, 0.72) 55%, rgba(28, 31, 29, 0.92) 100%);
  --font-heading: STZhongsong, "Source Han Serif SC", "Songti SC", SimSun, serif;
  --font-body: "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 9.8px;
  --text-sm: 14.7px;
  --text-base: 18px;
  --text-lg: 27.0px;
  --text-xl: 40.5px;
  --text-2xl: 60.8px;
  --text-3xl: 91.1px;
  --text-4xl: 136.7px;
  --text-display: clamp(47px, 9.7vw, 124px);
  --text-figure: clamp(39px, 7.0vw, 89px);
  --weight-heading: 426;
  --weight-body: 400;
  --leading-body: 1.85;
  --leading-heading: 1.24;
  --tracking-heading: -0.007em;
  --radius-sm: 0px;
  --radius-md: 0px;
  --radius-lg: 0px;
  --radius-pill: 0px;
  --border-thin: 1px;
  --border-thick: 1px;
  --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: 960px;
  --measure: 66ch;
  --gutter: 24px;
  --section-y: 103px;
  --section-y-lg: 144px;
}

/* 运行期派生变量：非同名，仅供轨道宽度与动效节奏使用 */
:root {
  --rail: 200px;
  --dur-quick: 180ms;
  --dur-base: 240ms;
  --ease-out: cubic-bezier(0.2, 0, 0, 1);
}

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 92px;
  background: var(--color-surface);
}

body,
h1, h2, h3, h4, h5, h6,
p, figure, figcaption, blockquote,
dl, dd, ul, ol {
  margin: 0;
}

ul, ol { padding: 0; list-style: none; }

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

button {
  font: inherit;
  color: inherit;
  background: none;
  border: 0;
  padding: 0;
  cursor: pointer;
}

a { color: var(--color-accent); text-decoration: none; }

:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 3px;
}

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

/* ==========================================================================
   2. 基准排版
   ========================================================================== */
body {
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  color: var(--color-ink);
  background: var(--color-surface);
  letter-spacing: 0.012em;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
  text-wrap: balance;
}

h1 { font-size: var(--text-display); }
h2 { font-size: var(--text-xl); }
h3 { font-size: var(--text-lg); }
h4 { font-size: var(--text-base); font-weight: 600; }

p { text-wrap: pretty; }

.mono,
.num,
time {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-feature-settings: "tnum" 1;
}

.lede {
  font-family: var(--font-body);
  font-size: var(--text-lg);
  line-height: 1.6;
  color: var(--color-ink-soft);
  max-width: var(--measure);
}

.note {
  font-size: var(--text-sm);
  line-height: 1.7;
  color: var(--color-ink-muted);
}

.eyebrow {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

/* ==========================================================================
   3. 布局
   ========================================================================== */
.container {
  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--tight { padding-block: var(--space-8); }
.section--alt { background: var(--color-surface-alt); }
.section--deep { background: var(--color-surface-deep); }

.grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--gutter);
  align-items: start;
}

.col-3 { grid-column: span 3; }
.col-4 { grid-column: span 4; }
.col-5 { grid-column: span 5; }
.col-6 { grid-column: span 6; }
.col-7 { grid-column: span 7; }
.col-8 { grid-column: span 8; }
.col-9 { grid-column: span 9; }
.col-12 { grid-column: span 12; }

@media (max-width: 899px) {
  .col-3, .col-4, .col-5, .col-6,
  .col-7, .col-8, .col-9 { grid-column: span 12; }
}

.stack > * + * { margin-top: var(--space-3); }
.stack--lg > * + * { margin-top: var(--space-6); }

/* ==========================================================================
   4. 章节标题与刻度分隔
   ========================================================================== */
.sec-head {
  display: flex;
  align-items: baseline;
  gap: var(--space-3);
  flex-wrap: wrap;
  margin-bottom: var(--space-6);
}

.sec-head__num {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.12em;
  color: var(--color-primary);
  font-variant-numeric: tabular-nums;
}

.sec-head__title {
  font-family: var(--font-heading);
  font-size: var(--text-xl);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  font-weight: var(--weight-heading);
}

.sec-head__aside {
  margin-left: auto;
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}

.rule-scale {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  align-items: center;
  padding-block: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  color: var(--color-ink-muted);
  background-image: repeating-linear-gradient(
    to right,
    var(--color-line) 0 1px,
    transparent 1px 16px
  );
  background-repeat: no-repeat;
  background-position: left top;
  background-size: 100% 1px;
  padding-top: var(--space-3);
}

/* ==========================================================================
   5. 深色数据带
   ========================================================================== */
.band {
  background-color: var(--color-contrast-surface);
  background-image:
    linear-gradient(to right, color-mix(in srgb, var(--color-contrast-ink) 7%, transparent) 1px, transparent 1px),
    linear-gradient(to bottom, color-mix(in srgb, var(--color-contrast-ink) 7%, transparent) 1px, transparent 1px);
  background-size: 56px 56px;
  color: var(--color-contrast-ink);
  padding-block: var(--section-y);
}

.band h1, .band h2, .band h3, .band h4 { color: var(--color-contrast-ink); }
.band .lede { color: color-mix(in srgb, var(--color-contrast-ink) 78%, transparent); }
.band .eyebrow,
.band .note { color: color-mix(in srgb, var(--color-contrast-ink) 60%, transparent); }
.band .sec-head__num { color: color-mix(in srgb, var(--color-contrast-ink) 55%, transparent); }
.band a { color: var(--color-contrast-accent); }
.band a:hover { color: var(--color-contrast-accent); text-decoration: underline; text-underline-offset: 0.24em; }

.band .rule-scale {
  color: color-mix(in srgb, var(--color-contrast-ink) 55%, transparent);
  background-image: repeating-linear-gradient(
    to right,
    var(--color-contrast-line) 0 1px,
    transparent 1px 16px
  );
}

/* ==========================================================================
   6. 数据点
   ========================================================================== */
.stat { display: flex; flex-direction: column; gap: var(--space-1); }

.stat__value {
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  line-height: 0.94;
  letter-spacing: -0.03em;
  font-variant-numeric: tabular-nums;
  color: var(--color-ink);
}

.stat__label {
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  letter-spacing: 0.04em;
}

.band .stat__value { color: var(--color-contrast-accent); }
.band .stat__label { color: color-mix(in srgb, var(--color-contrast-ink) 62%, transparent); }

/* ==========================================================================
   7. 正文长文档
   ========================================================================== */
.prose {
  max-width: var(--measure);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink);
}

.prose > * + * { margin-top: var(--space-3); }
.prose > h2 { margin-top: var(--space-8); }
.prose > h3 { margin-top: var(--space-6); }

.prose h2 {
  font-family: var(--font-heading);
  font-size: var(--text-xl);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  font-weight: var(--weight-heading);
}

.prose h3 {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  line-height: var(--leading-heading);
  font-weight: var(--weight-heading);
}

.prose a {
  color: var(--color-accent);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.26em;
}

.prose a:hover { color: var(--color-focus); }

.prose ul,
.prose ol {
  max-width: var(--measure);
}

.prose li {
  position: relative;
  padding-left: 2.2em;
}

.prose li + li { margin-top: var(--space-1); }

.prose ul > li::before {
  content: "—";
  position: absolute;
  left: 0;
  color: var(--color-primary);
  font-family: var(--font-mono);
}

.prose ol { counter-reset: prose-ol; }

.prose ol > li::before {
  counter-increment: prose-ol;
  content: counter(prose-ol, decimal-leading-zero);
  position: absolute;
  left: 0;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-primary);
}

.prose strong { font-weight: 600; color: var(--color-ink); }

.callout {
  background: var(--color-highlight);
  padding: var(--space-3) var(--space-4);
  max-width: var(--measure);
}

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

/* ==========================================================================
   8. 编号列表与对照
   ========================================================================== */
.numlist { display: flex; flex-direction: column; }

.numlist__item {
  display: grid;
  grid-template-columns: 3.6em minmax(0, 1fr);
  gap: var(--space-2);
  padding-block: var(--space-3);
  align-items: baseline;
}

.numlist__item + .numlist__item {
  background-image: linear-gradient(to right, var(--color-line) 0 100%);
  background-repeat: no-repeat;
  background-position: left top;
  background-size: 100% 1px;
}

.numlist__num {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-primary);
  letter-spacing: 0.08em;
}

.numlist__body > * + * { margin-top: var(--space-1); }

.compare {
  width: 100%;
  border-collapse: collapse;
  font-size: var(--text-base);
}

.compare th,
.compare td {
  text-align: left;
  padding: var(--space-3) var(--space-3) var(--space-3) 0;
  vertical-align: top;
}

.compare thead th {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 400;
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
  background: var(--color-surface-deep);
  padding-inline: var(--space-2);
}

.compare tbody tr + tr {
  background-image: linear-gradient(to right, var(--color-line) 0 100%);
  background-repeat: no-repeat;
  background-position: left top;
  background-size: 100% 1px;
}

.compare tbody th {
  font-family: var(--font-body);
  font-weight: 600;
  white-space: nowrap;
}

/* ==========================================================================
   9. 图片容器
   ========================================================================== */
.frame {
  position: relative;
  display: block;
  overflow: hidden;
  background: var(--color-surface-deep);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-1);
}

.frame > img,
.frame > picture > img,
.frame > svg,
.frame > video {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.frame--cinema { aspect-ratio: 2.39 / 1; }
.frame--wide { aspect-ratio: 21 / 9; }
.frame--square { aspect-ratio: 1 / 1; }
.frame--portrait { aspect-ratio: 4 / 5; }
.frame--tall { aspect-ratio: 3 / 5; }
.frame--auto { aspect-ratio: auto; }

.frame__caption {
  position: absolute;
  inset-inline: 0;
  bottom: 0;
  padding: var(--space-3);
  background: var(--overlay-scrim);
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  line-height: 1.6;
  letter-spacing: 0.08em;
}

.frame--grid::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(to right, color-mix(in srgb, var(--color-contrast-ink) 12%, transparent) 1px, transparent 1px),
    linear-gradient(to bottom, color-mix(in srgb, var(--color-contrast-ink) 12%, transparent) 1px, transparent 1px);
  background-size: 48px 48px;
}

/* ==========================================================================
   10. 面包屑与按钮
   ========================================================================== */
.crumbs {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.crumbs ol {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1) var(--space-2);
  align-items: center;
}

.crumbs li { display: inline-flex; align-items: center; gap: var(--space-2); }

.crumbs li + li::before {
  content: "/";
  color: var(--color-line);
}

.crumbs a { color: var(--color-ink-muted); }
.crumbs a:hover { color: var(--color-accent); }
.crumbs [aria-current="page"] { color: var(--color-ink); }

.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  border-radius: var(--radius-sm);
  transition: color var(--dur-quick) var(--ease-out),
              background-color var(--dur-quick) var(--ease-out);
}

.btn--solid {
  background: var(--color-accent);
  color: var(--color-accent-ink);
  padding: var(--space-2) var(--space-4);
}

.btn--solid:hover { background: var(--color-focus); }

.btn--ghost {
  color: var(--color-accent);
  padding-block: var(--space-1);
  border-bottom: var(--border-thin) solid currentColor;
}

.btn--ghost:hover { color: var(--color-focus); }

.btn--quiet {
  color: var(--color-ink);
  padding-block: var(--space-1);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.btn--quiet:hover { color: var(--color-accent); border-bottom-color: var(--color-accent); }

/* ==========================================================================
   11. 标签页与目录
   ========================================================================== */
.tabs { display: block; }

.tabs__list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
  margin-bottom: var(--space-6);
}

.tabs__tab {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
  padding-block: var(--space-2);
  border-bottom: var(--border-thin) solid transparent;
  transition: color var(--dur-quick) var(--ease-out),
              border-color var(--dur-quick) var(--ease-out);
}

.tabs__tab:hover { color: var(--color-ink); }

.tabs__tab[aria-selected="true"] {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
}

.tabs__panel[hidden] { display: none; }
.tabs__panel > * + * { margin-top: var(--space-4); }

.toc {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
}

.toc ol { display: flex; flex-direction: column; gap: var(--space-2); }

.toc a {
  display: grid;
  grid-template-columns: 2.6em minmax(0, 1fr);
  gap: var(--space-1);
  color: var(--color-ink-muted);
  padding-block: var(--space-1);
  transition: color var(--dur-quick) var(--ease-out);
}

.toc a:hover { color: var(--color-accent); }

.toc a[aria-current="true"] {
  color: var(--color-accent);
  font-weight: 600;
}

/* ==========================================================================
   12. 显示与显现
   ========================================================================== */
.reveal {
  transition: opacity var(--dur-base) var(--ease-out),
              transform var(--dur-base) var(--ease-out);
}

html.js .reveal {
  opacity: 0;
  transform: translateY(8px);
}

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

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* ==========================================================================
   13. 头部
   ========================================================================== */
.skip-link {
  position: fixed;
  top: var(--space-2);
  left: var(--space-2);
  z-index: 300;
  padding: var(--space-2) var(--space-3);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.1em;
  transform: translateY(-260%);
  transition: transform var(--dur-quick) var(--ease-out);
}

.skip-link:focus {
  transform: translateY(0);
  color: var(--color-contrast-ink);
}

.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 2px;
  transform: scaleX(0);
  transform-origin: left center;
  background: var(--color-accent);
  z-index: 120;
  pointer-events: none;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 60;
  background: var(--color-surface);
}

.site-header::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 1px;
  background: var(--color-line);
}

.site-header__inner {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  width: 100%;
  padding: var(--space-3) var(--gutter);
}

.site-brand { display: flex; flex-direction: column; gap: 2px; }

.site-brand__link {
  display: inline-flex;
  align-items: baseline;
  color: var(--color-ink);
}

.site-brand__mark,
.site-brand__name {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  letter-spacing: 0.02em;
  line-height: 1.1;
}

.site-brand__mark { text-transform: uppercase; letter-spacing: 0.04em; }
.site-brand__name { margin-left: 0.2em; }

.site-brand__note {
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-ink-muted);
  font-family: var(--font-mono);
}

.nav-toggle {
  margin-left: auto;
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-1) 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  color: var(--color-ink);
  position: relative;
  z-index: 90;
}

.nav-toggle__label { text-transform: uppercase; }

.nav-toggle__bars {
  position: relative;
  display: block;
  width: 22px;
  height: 1px;
  background: currentColor;
}

.nav-toggle__bars::before,
.nav-toggle__bars::after {
  content: "";
  position: absolute;
  left: 0;
  width: 22px;
  height: 1px;
  background: currentColor;
  transition: transform var(--dur-quick) var(--ease-out);
}

.nav-toggle__bars::before { top: -6px; }
.nav-toggle__bars::after { top: 6px; }

.site-header[data-open] .nav-toggle__bars { background: transparent; }
.site-header[data-open] .nav-toggle__bars::before { transform: translateY(6px) rotate(45deg); }
.site-header[data-open] .nav-toggle__bars::after { transform: translateY(-6px) rotate(-45deg); }

.site-nav__head {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  padding-bottom: var(--space-3);
}

.site-nav__list {
  padding-left: var(--space-3);
  background-image: repeating-linear-gradient(
    to bottom,
    var(--color-line) 0 1px,
    transparent 1px 12px
  );
  background-repeat: no-repeat;
  background-position: left top;
  background-size: 1px 100%;
}

.site-nav__link {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  padding: var(--space-2) 0;
  font-size: var(--text-sm);
  line-height: 1.45;
  color: var(--color-ink);
  transition: color var(--dur-quick) var(--ease-out),
              padding-left var(--dur-quick) var(--ease-out);
}

.site-nav__idx {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
  min-width: 2.2em;
  transition: color var(--dur-quick) var(--ease-out);
}

.site-nav__link:hover {
  color: var(--color-accent);
  padding-left: var(--space-1);
}

.site-nav__link[aria-current="page"] {
  color: var(--color-accent);
  font-weight: 600;
}

.site-nav__link[aria-current="page"] .site-nav__idx { color: var(--color-accent); }

.site-header__cta {
  display: none;
  align-self: flex-start;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.16em;
  color: var(--color-accent);
  padding-bottom: 2px;
  border-bottom: var(--border-thin) solid currentColor;
}

.site-header__cta:hover { color: var(--color-focus); }

/* —— 移动端抽屉 —— */
@media (max-width: 1023.98px) {
  .site-nav {
    display: none;
    position: fixed;
    inset: 0;
    z-index: 70;
    background: var(--color-surface);
    padding: var(--space-8) var(--gutter) var(--space-6);
    overflow-y: auto;
    flex-direction: column;
  }

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

  .site-nav__list { padding-left: var(--space-3); }

  .site-nav__link { font-size: var(--text-lg); padding: var(--space-2) 0; }

  .site-nav__idx { font-size: var(--text-sm); }

  .site-header[data-open] .site-brand { opacity: 0.25; }
}

/* —— 桌面端固定轨道 —— */
@media (min-width: 1024px) {
  body { padding-left: var(--rail); }

  .site-header {
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    width: var(--rail);
    display: flex;
    flex-direction: column;
    overflow-y: auto;
    padding: var(--space-8) var(--space-3) var(--space-4);
    background: var(--color-surface);
  }

  .site-header::after {
    left: auto;
    right: 0;
    top: 0;
    bottom: 0;
    width: 1px;
    height: auto;
  }

  .site-header__inner {
    flex-direction: column;
    align-items: stretch;
    justify-content: space-between;
    gap: var(--space-6);
    height: 100%;
    padding: 0;
  }

  .nav-toggle { display: none; }

  .site-nav { display: block; }

  .site-nav__link { font-size: var(--text-sm); }

  .site-header__cta { display: inline-block; }

  .skip-link { left: calc(var(--rail) + var(--space-2)); }
}

/* ==========================================================================
   14. 页脚
   ========================================================================== */
.site-footer {
  padding-block: var(--space-6) var(--space-8);
  background: var(--color-surface);
  background-image: repeating-linear-gradient(
    to right,
    var(--color-line) 0 1px,
    transparent 1px 16px
  );
  background-repeat: no-repeat;
  background-position: left top;
  background-size: 100% 1px;
}

.site-footer__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-1) var(--space-2);
  font-size: var(--text-sm);
  line-height: 1.8;
}

.site-footer__brand {
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
  color: var(--color-ink);
}

.site-footer__sep {
  color: var(--color-line);
  font-family: var(--font-mono);
}

.site-footer__link {
  color: var(--color-accent);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.24em;
}

.site-footer__link:hover { color: var(--color-focus); }

.site-footer__icp,
.site-footer__year {
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  font-family: var(--font-mono);
  letter-spacing: 0.04em;
}

/* ==========================================================================
   15. 响应式与动效降级
   ========================================================================== */
@media (max-width: 767.98px) {
  .section { padding-block: var(--space-8); }
  .section--lg { padding-block: var(--section-y); }
  .lede { font-size: var(--text-base); }
  .sec-head { margin-bottom: var(--space-4); }
  .sec-head__aside { margin-left: 0; }
  .tabs__list { gap: var(--space-3); }
  .numlist__item { grid-template-columns: 2.8em minmax(0, 1fr); }
  .compare { font-size: var(--text-sm); }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  html.js .reveal,
  html.js .reveal.is-visible {
    opacity: 1;
    transform: none;
  }

  .scroll-progress { transition: none; }
}