/* ============================================================
   雅虎中心 · 共享样式表 /assets/site.css
   珠宝深色骨架：深紫连续画布 + 细金属边界 + 浅色托块
   ============================================================ */

:root {
  --color-surface: #2c282c;
  --color-surface-alt: #3b363b;
  --color-surface-deep: #4c474d;
  --color-ink: #cec3d0;
  --color-ink-soft: #a491a6;
  --color-ink-muted: #89748b;
  --color-line: #49444a;
  --color-primary: #ba53c6;
  --color-primary-ink: #171118;
  --color-primary-soft: #402e42;
  --color-accent: #1de28d;
  --color-accent-ink: #171118;
  --color-highlight: #29493d;
  --color-focus: #10ef8e;
  --color-contrast-surface: #eeecef;
  --color-contrast-ink: #322e33;
  --color-contrast-line: #c5c2c6;
  --color-contrast-accent: #107a4c;
  --overlay-scrim: linear-gradient(180deg, rgba(238, 236, 239, 0.35) 0%, rgba(238, 236, 239, 0.72) 55%, rgba(238, 236, 239, 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: 11.0px;
  --text-sm: 14.7px;
  --text-base: 17px;
  --text-lg: 22.7px;
  --text-xl: 30.2px;
  --text-2xl: 40.3px;
  --text-3xl: 53.7px;
  --text-4xl: 71.5px;
  --text-display: clamp(41px, 8.5vw, 109px);
  --text-figure: clamp(34px, 6.1vw, 78px);
  --weight-heading: 570;
  --weight-body: 400;
  --leading-body: 1.74;
  --leading-heading: 1.25;
  --tracking-heading: 0.025em;
  --radius-sm: 7px;
  --radius-md: 7px;
  --radius-lg: 7px;
  --radius-pill: 7px;
  --border-thin: 1px;
  --border-thick: 2px;
  --shadow-1: 0 6px 18px rgba(206, 195, 208, 0.08);
  --shadow-2: 0 18px 44px rgba(206, 195, 208, 0.14);
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1180px;
  --measure: 65ch;
  --gutter: 16px;
  --section-y: 85px;
  --section-y-lg: 119px;
}

/* ---------- 派生层：一切颜色由定稿变量计算，不引入新色值 ---------- */
:root {
  --edge-metal: color-mix(in srgb, var(--color-primary) 42%, var(--color-line));
  --edge-soft: color-mix(in srgb, var(--color-line) 74%, var(--color-surface));
  --silk-rose: color-mix(in srgb, var(--color-primary) 74%, var(--color-accent) 26%);
  --silk-lake: color-mix(in srgb, var(--color-accent) 46%, var(--color-primary) 54%);
  --silk-sand: color-mix(in srgb, var(--color-primary) 22%, var(--color-contrast-surface));
  --veil-surface: color-mix(in srgb, var(--color-surface) 86%, transparent);
  --title-ink: color-mix(in srgb, var(--color-ink) 88%, var(--color-contrast-surface));
}

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

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

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);
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

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

ul,
ol { padding: 0; }

button { font: inherit; color: inherit; }

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color 200ms ease, border-color 200ms ease;
}

a:hover { color: color-mix(in srgb, var(--color-accent) 78%, var(--color-contrast-surface)); }

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

/* ---------- 中文排版 ---------- */
h1,
h2,
h3,
h4 {
  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);
  color: var(--title-ink);
  text-wrap: balance;
}

h1 { font-size: var(--text-3xl); }
h2 { font-size: var(--text-2xl); }
h3 { font-size: var(--text-xl); }
h4 { font-size: var(--text-lg); }

p { margin: 0 0 var(--space-2); }

.prose { max-width: var(--measure); }
.prose p { margin: 0 0 var(--space-3); }
.prose > :last-child { margin-bottom: 0; }

.lead {
  font-size: var(--text-lg);
  line-height: 1.55;
  color: var(--color-ink);
}

.eyebrow {
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.22em;
  color: var(--color-ink-muted);
}

.mono {
  font-family: var(--font-mono);
  font-size: 0.94em;
  letter-spacing: 0.02em;
}

.rule {
  height: var(--border-thin);
  border: 0;
  margin: var(--space-6) 0;
  background-color: var(--color-line);
}

/* ---------- 布局 ---------- */
.container {
  width: min(var(--container), calc(100% - var(--gutter) * 2));
  margin-inline: auto;
}

.section { padding-block: var(--section-y); }
.section--lg { padding-block: var(--section-y-lg); }

.grid {
  display: grid;
  gap: var(--gutter);
}

.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-4 { grid-column: span 4; }
.span-6 { grid-column: span 6; }
.span-8 { grid-column: span 8; }
.span-12 { grid-column: span 12; }

/* ---------- 面包屑 ---------- */
.crumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1);
  margin: 0 0 var(--space-3);
  padding: 0;
  list-style: none;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  color: var(--color-ink-muted);
}

.crumbs a { color: var(--color-ink-soft); }
.crumbs a:hover { color: var(--color-accent); }

.crumbs li + li::before {
  content: "/";
  margin-right: var(--space-1);
  color: var(--color-line);
}

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  padding: 11px 18px;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-sm);
  background-color: transparent;
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-sm);
  letter-spacing: 0.03em;
  cursor: pointer;
  transition: background-color 200ms ease, border-color 200ms ease, color 200ms ease, transform 200ms ease;
}

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

.btn--primary:hover {
  background-color: color-mix(in srgb, var(--color-primary) 78%, var(--color-accent));
  color: var(--color-primary-ink);
  transform: translateY(-1px);
}

.btn--ghost {
  border-color: var(--edge-metal);
  color: var(--color-ink);
}

.btn--ghost:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
  transform: translateY(-1px);
}

.btn--contrast {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.btn--contrast:hover {
  background-color: var(--silk-sand);
  color: var(--color-contrast-ink);
}

.link-arrow {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  font-size: var(--text-sm);
  color: var(--color-accent);
  border-bottom: var(--border-thin) solid transparent;
  padding-bottom: 2px;
}

.link-arrow::after {
  content: "→";
  transition: transform 200ms ease;
}

.link-arrow:hover {
  border-bottom-color: currentColor;
  color: color-mix(in srgb, var(--color-accent) 80%, var(--color-contrast-surface));
}

.link-arrow:hover::after { transform: translateX(3px); }

/* ---------- 徽标 ---------- */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 10px;
  border: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 38%, var(--color-line));
  border-radius: var(--radius-sm);
  background-color: color-mix(in srgb, var(--color-highlight) 72%, transparent);
  color: color-mix(in srgb, var(--color-accent) 76%, var(--color-ink));
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  white-space: nowrap;
}

.badge::before {
  content: "";
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--color-accent);
}

/* ---------- 托起色块 ---------- */
.slab {
  padding: var(--space-4);
  border: var(--border-thin) solid var(--edge-soft);
  border-radius: var(--radius-md);
  background-color: color-mix(in srgb, var(--color-surface-alt) 68%, transparent);
}

.slab--contrast {
  background-color: var(--color-contrast-surface);
  border-color: var(--color-contrast-line);
  color: var(--color-contrast-ink);
}

.slab--contrast h1,
.slab--contrast h2,
.slab--contrast h3,
.slab--contrast h4 { color: var(--color-contrast-ink); }

.slab--contrast p,
.slab--contrast li { color: var(--color-contrast-ink); }

.slab--contrast .slab__num,
.slab--contrast .eyebrow { color: var(--color-contrast-accent); }

.slab--highlight {
  background-color: var(--color-highlight);
  border-color: color-mix(in srgb, var(--color-accent) 30%, var(--color-line));
}

.slab--primary {
  background-color: var(--color-primary-soft);
  border-color: var(--edge-metal);
}

.slab__num {
  display: block;
  margin: 0 0 var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--color-accent);
}

/* ---------- 图片容器（供页面阶段放置占位与图录式图片） ---------- */
.media {
  position: relative;
  overflow: hidden;
  border: var(--border-thin) solid var(--edge-soft);
  border-radius: var(--radius-md);
  background-color: color-mix(in srgb, var(--color-surface-deep) 78%, transparent);
}

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

.media--16x9 { aspect-ratio: 16 / 9; }
.media--4x3 { aspect-ratio: 4 / 3; }
.media--1x1 { aspect-ratio: 1 / 1; }

.media--geo {
  background-image:
    repeating-linear-gradient(135deg, color-mix(in srgb, var(--color-primary) 26%, transparent) 0 12px, transparent 12px 26px),
    radial-gradient(circle at 28% 18%, color-mix(in srgb, var(--silk-lake) 24%, transparent), transparent 62%),
    radial-gradient(circle at 78% 82%, color-mix(in srgb, var(--silk-rose) 20%, transparent), transparent 58%);
}

.media__scrim {
  position: absolute;
  inset: 0;
  background-image: var(--overlay-scrim);
  pointer-events: none;
}

.media__cap {
  position: absolute;
  inset-inline: var(--space-3);
  bottom: var(--space-2);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  line-height: 1.45;
}

/* ---------- 跳转链接 ---------- */
.skip-link {
  position: fixed;
  top: var(--space-1);
  left: var(--space-1);
  z-index: 200;
  padding: 10px 16px;
  border: var(--border-thin) solid var(--color-contrast-line);
  border-radius: var(--radius-sm);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  transform: translateY(-220%);
  transition: transform 200ms ease;
}

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

/* ---------- 头部 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 90;
  padding: 12px 0 10px;
  background-color: var(--veil-surface);
  border-bottom: var(--border-thin) solid transparent;
  backdrop-filter: blur(10px);
  transition: border-color 240ms ease, background-color 240ms ease;
}

.site-header[data-scrolled] {
  border-bottom-color: var(--edge-soft);
  background-color: color-mix(in srgb, var(--color-surface) 95%, transparent);
}

.edge-rail {
  position: fixed;
  left: 20px;
  top: 50%;
  z-index: 95;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  padding: 14px 10px;
  border: var(--border-thin) solid var(--edge-soft);
  border-radius: var(--radius-md);
  background-color: color-mix(in srgb, var(--color-surface-deep) 88%, transparent);
  box-shadow: var(--shadow-1);
  transition: border-color 220ms ease, box-shadow 220ms ease;
}

.edge-rail:hover {
  border-color: var(--edge-metal);
  box-shadow: var(--shadow-2);
}

.edge-rail__mark {
  margin: 0;
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  line-height: 1;
  color: var(--color-primary);
}

.edge-rail__stack {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.edge-rail__btn {
  writing-mode: vertical-rl;
  padding: 12px 8px;
  border: var(--border-thin) solid var(--edge-soft);
  border-radius: var(--radius-sm);
  background-color: transparent;
  color: var(--color-ink-soft);
  font-family: var(--font-body);
  font-size: var(--text-xs);
  letter-spacing: 0.24em;
  cursor: pointer;
  transition: color 200ms ease, border-color 200ms ease, background-color 200ms ease;
}

.edge-rail__btn:hover {
  color: var(--color-ink);
  border-color: var(--edge-metal);
}

.edge-rail__btn[aria-expanded="true"] {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}

.edge-rail__panel {
  position: absolute;
  left: calc(100% + 12px);
  top: 0;
  width: 272px;
  padding: var(--space-3);
  border: var(--border-thin) solid var(--edge-metal);
  border-radius: var(--radius-md);
  background-color: var(--color-surface-alt);
  box-shadow: var(--shadow-2);
}

.edge-rail__panel[hidden] { display: none; }

.rail-note__title {
  margin: 0 0 var(--space-1);
  font-size: var(--text-lg);
}

.rail-note__text {
  margin: 0 0 var(--space-2);
  font-size: var(--text-sm);
  line-height: 1.6;
  color: var(--color-ink-soft);
}

.bar {
  display: flex;
  justify-content: center;
  padding-inline: var(--gutter);
}

.bar__inner {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  width: min(var(--container), 100%);
  padding: 10px 12px 10px 20px;
  border: var(--border-thin) solid var(--edge-soft);
  border-radius: var(--radius-pill);
  background-color: color-mix(in srgb, var(--color-surface-alt) 88%, transparent);
  box-shadow: var(--shadow-1);
  transition: border-color 240ms ease, box-shadow 240ms ease, background-color 240ms ease;
}

.site-header[data-scrolled] .bar__inner {
  border-color: var(--edge-metal);
  background-color: color-mix(in srgb, var(--color-surface-alt) 96%, transparent);
  box-shadow: var(--shadow-2);
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  flex: 0 0 auto;
  color: var(--color-ink);
}

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

.brand__mark {
  font-family: var(--font-heading);
  font-size: var(--text-xl);
  font-weight: var(--weight-heading);
  letter-spacing: 0.1em;
  line-height: 1.1;
}

.brand__rule {
  width: 44px;
  height: var(--border-thin);
  background-color: var(--edge-metal);
  transition: width 220ms ease, background-color 220ms ease;
}

.brand:hover .brand__rule {
  width: 62px;
  background-color: var(--color-primary);
}

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

.nav {
  margin-inline: auto;
}

.nav__list {
  display: flex;
  align-items: center;
  gap: 2px;
  margin: 0;
  list-style: none;
}

.nav__link {
  display: block;
  padding: 9px 14px;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-sm);
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  letter-spacing: 0.03em;
  white-space: nowrap;
  transition: color 200ms ease, background-color 200ms ease, border-color 200ms ease;
}

.nav__link:hover {
  color: var(--color-ink);
  border-color: var(--edge-soft);
  background-color: color-mix(in srgb, var(--color-surface-deep) 62%, transparent);
}

.nav__link[aria-current="page"] {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}

.bar__aside {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex: 0 0 auto;
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-1);
  padding: 9px 12px;
  border: var(--border-thin) solid var(--edge-soft);
  border-radius: var(--radius-sm);
  background-color: transparent;
  color: var(--color-ink);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  cursor: pointer;
  transition: border-color 200ms ease, color 200ms ease;
}

.nav-toggle__icon {
  display: flex;
  flex-direction: column;
  gap: 4px;
  width: 14px;
}

.nav-toggle__bar {
  display: block;
  width: 100%;
  height: var(--border-thin);
  background-color: currentColor;
  transition: transform 220ms ease;
}

.nav-toggle:hover { border-color: var(--edge-metal); }

.nav-toggle[aria-expanded="true"] {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__bar:first-child {
  transform: translateY(2.5px) rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__bar:last-child {
  transform: translateY(-2.5px) rotate(-45deg);
}

/* ---------- 页脚 ---------- */
.site-footer {
  margin-top: var(--section-y-lg);
  padding: var(--space-8) 0 var(--space-4);
  border-top: var(--border-thin) solid var(--edge-metal);
  background-image: linear-gradient(180deg, color-mix(in srgb, var(--color-surface-deep) 94%, transparent) 0%, var(--color-surface-deep) 42%);
}

.footer__grid {
  display: grid;
  grid-template-columns: 1.5fr 0.85fr 0.85fr 0.62fr;
  gap: var(--space-6);
  align-items: start;
}

.footer__mark {
  margin: 0 0 var(--space-2);
  font-family: var(--font-heading);
  font-size: var(--text-2xl);
  letter-spacing: 0.08em;
  color: var(--title-ink);
}

.footer__lead {
  max-width: 32ch;
  margin: 0 0 var(--space-3);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

.footer__line {
  margin: 0 0 6px;
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  word-break: break-word;
}

.footer__title {
  margin: 0 0 var(--space-2);
  padding-bottom: 10px;
  border-bottom: var(--border-thin) solid var(--color-line);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: var(--weight-body);
  letter-spacing: 0.2em;
  color: var(--color-ink-muted);
}

.footer__list {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  margin: 0;
  list-style: none;
}

.footer__list a,
.footer__plain {
  font-size: var(--text-sm);
  color: var(--color-ink);
  border-bottom: var(--border-thin) solid transparent;
}

.footer__plain { color: var(--color-ink-soft); }

.footer__list a:hover {
  color: var(--color-accent);
  border-bottom-color: color-mix(in srgb, var(--color-accent) 55%, transparent);
}

.footer__panel {
  margin-top: var(--space-8);
  border-top: var(--border-thin) solid var(--color-line);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.panel-toggle {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
  width: 100%;
  padding: var(--space-3) 0;
  border: 0;
  background-color: transparent;
  color: var(--color-ink);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  letter-spacing: var(--tracking-heading);
  text-align: left;
  cursor: pointer;
  transition: color 200ms ease;
}

.panel-toggle:hover { color: var(--color-accent); }

.panel-toggle[aria-expanded="true"] { color: var(--color-primary); }

.panel-toggle__hint {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  color: var(--color-ink-muted);
}

.panel-body {
  max-width: var(--measure);
  padding: 0 0 var(--space-4);
  font-size: var(--text-sm);
  line-height: 1.7;
  color: var(--color-ink-soft);
}

.panel-body[hidden] { display: none; }

.panel-body.is-flash {
  animation: panel-flash 480ms ease-out 1;
}

@keyframes panel-flash {
  0% { opacity: 0; transform: translateY(-6px); }
  100% { opacity: 1; transform: translateY(0); }
}

.footer__legal {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
  margin-top: var(--space-4);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  color: var(--color-ink-muted);
}

.footer__copy { margin: 0; }

.footer__legal-links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin: 0;
}

.footer__legal-links a { color: var(--color-ink-muted); }
.footer__legal-links a:hover { color: var(--color-accent); }

/* ---------- 滚动显现 ---------- */
.js-reveal [data-reveal] {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 260ms ease, transform 260ms ease;
}

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

/* ---------- 响应式 ---------- */
@media (max-width: 1400px) {
  .edge-rail {
    left: var(--space-2);
    top: auto;
    bottom: var(--space-3);
    transform: none;
    flex-direction: row;
    padding: 8px 12px;
  }

  .edge-rail__stack { flex-direction: row; }

  .edge-rail__btn {
    writing-mode: horizontal-tb;
    padding: 8px 12px;
    letter-spacing: 0.1em;
  }

  .edge-rail__panel {
    left: 0;
    top: auto;
    bottom: calc(100% + 10px);
    width: min(288px, calc(100vw - 32px));
  }
}

@media (max-width: 1080px) {
  .brand__note { display: none; }
  .nav__link { padding: 9px 11px; }
}

@media (max-width: 900px) {
  .bar__inner {
    flex-wrap: wrap;
    padding: 10px 12px;
    gap: var(--space-2);
    border-radius: var(--radius-md);
  }

  .brand__mark { font-size: var(--text-lg); }
  .brand__rule { width: 26px; }

  .nav-toggle { display: inline-flex; margin-left: auto; }

  .bar__aside {
    order: 2;
    margin-left: auto;
  }

  .bar__aside .badge { display: none; }

  .nav {
    order: 3;
    flex: 1 0 100%;
    display: none;
    margin: 0;
    padding-top: var(--space-1);
    border-top: var(--border-thin) solid var(--edge-soft);
  }

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

  .nav__list {
    flex-direction: column;
    align-items: stretch;
  }

  .nav__link { padding: 12px; }

  .footer__grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: var(--space-4);
  }

  .footer__brand { grid-column: 1 / -1; }

  .grid--3,
  .grid--4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }

  .span-4,
  .span-6,
  .span-8 { grid-column: span 12; }
}

@media (max-width: 640px) {
  .grid--2,
  .grid--3,
  .grid--4 { grid-template-columns: minmax(0, 1fr); }

  .footer__grid { grid-template-columns: minmax(0, 1fr); }

  h1 { font-size: var(--text-2xl); }
  h2 { font-size: var(--text-xl); }

  .slab { padding: var(--space-3); }

  .footer__legal { flex-direction: column; align-items: flex-start; }
}

/* ---------- 动效与可访问性降级 ---------- */
@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;
  }

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

  .link-arrow:hover::after { transform: none; }
  .btn:hover { transform: none; }
}