.page-about {
  --about-rail: 168px;
  --about-edge: color-mix(in srgb, var(--color-primary) 42%, transparent);
  --about-edge-soft: color-mix(in srgb, var(--color-primary) 16%, transparent);
}

.page-about .about-crumbs {
  padding-top: var(--space-3);
}

/* ---------- 首屏 ---------- */
.page-about .about-lead {
  position: relative;
  padding-block: var(--space-6) var(--space-6);
  background:
    radial-gradient(120% 85% at 8% -20%, color-mix(in srgb, var(--color-primary) 16%, transparent) 0%, transparent 62%),
    radial-gradient(90% 70% at 100% 0%, color-mix(in srgb, var(--color-accent) 7%, transparent) 0%, transparent 58%);
}

.page-about .about-lead__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-6);
}

.page-about .about-lead__title {
  margin: var(--space-2) 0 var(--space-4);
  font-family: var(--font-heading);
  font-size: var(--text-xl);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
  max-width: 26ch;
}

.page-about .about-lead__text {
  margin: 0 0 var(--space-3);
  max-width: var(--measure);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

.page-about .about-lead__text:last-child {
  margin-bottom: 0;
}

/* 状态面板 */
.page-about .about-status {
  align-self: start;
}

.page-about .about-status__title {
  margin: 0 0 var(--space-2);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-primary);
  text-transform: uppercase;
}

.page-about .about-status__list {
  margin: 0;
  display: grid;
  gap: 0;
}

.page-about .about-status__row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: var(--space-3);
  padding-block: var(--space-2);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.page-about .about-status__row:last-child {
  border-bottom: 0;
  padding-bottom: 0;
}

.page-about .about-status__key {
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}

.page-about .about-status__val {
  margin: 0;
  font-size: var(--text-sm);
  color: var(--color-accent);
  text-align: right;
}

/* ---------- 页内章节导航 ---------- */
.page-about .about-toc {
  border-top: var(--border-thin) solid var(--color-line);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.page-about .about-toc__list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-4);
  margin: 0;
  padding: var(--space-3) 0;
  list-style: none;
}

.page-about .about-toc__link {
  display: inline-flex;
  align-items: baseline;
  gap: var(--space-1);
  padding-bottom: 2px;
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  text-decoration: none;
  border-bottom: var(--border-thin) solid transparent;
  transition: color 160ms ease, border-color 160ms ease;
}

.page-about .about-toc__link:hover,
.page-about .about-toc__link:focus-visible {
  color: var(--color-ink);
  border-bottom-color: var(--color-primary);
}

.page-about .about-toc__link[aria-current="true"] {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.page-about .about-toc__num {
  font-size: var(--text-xs);
  color: var(--color-primary);
}

/* ---------- 章节通用骨架 ---------- */
.page-about .about-chapter__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-3);
}

.page-about .about-chapter__aside {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
}

.page-about .about-chapter__num {
  font-size: var(--text-xl);
  line-height: 1;
  color: var(--color-primary);
}

.page-about .about-chapter__label {
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  color: var(--color-ink-muted);
}

.page-about .about-chapter__title {
  margin: 0 0 var(--space-3);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
  max-width: 30ch;
}

.page-about .about-chapter__text {
  margin: 0 0 var(--space-3);
  max-width: var(--measure);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

.page-about .about-chapter__text:last-child {
  margin-bottom: 0;
}

.page-about .about-chapter__link {
  color: var(--color-ink);
  text-decoration: none;
  border-bottom: var(--border-thin) solid var(--about-edge);
  transition: color 160ms ease, border-color 160ms ease;
}

.page-about .about-chapter__link:hover,
.page-about .about-chapter__link:focus-visible {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.page-about .about-chapter__figure {
  margin: var(--space-4) 0 0;
}

/* ---------- 规模数字 ---------- */
.page-about .about-scale {
  margin-block: var(--space-4) var(--space-4);
}

.page-about .about-scale__headline {
  padding-bottom: var(--space-3);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.page-about .about-scale__num {
  display: block;
  font-size: var(--text-figure);
  line-height: 1;
  color: var(--color-accent);
  letter-spacing: -0.02em;
}

.page-about .about-scale__caption {
  display: block;
  margin-top: var(--space-2);
  max-width: var(--measure);
  font-size: var(--text-sm);
  line-height: 1.6;
  color: var(--color-ink-soft);
}

.page-about .about-scale__list {
  margin: var(--space-4) 0 0;
  display: grid;
  border-top: var(--border-thin) solid var(--color-line);
}

.page-about .about-scale__item {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-1);
  padding-block: var(--space-2);
  border-bottom: var(--border-thin) solid var(--color-line);
}

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

.page-about .about-scale__desc {
  margin: 0;
  font-size: var(--text-base);
  line-height: 1.55;
  color: var(--color-ink);
}

.page-about .about-scale__val {
  font-size: var(--text-lg);
  line-height: 1;
  color: var(--color-accent);
  padding-inline: 2px;
}

/* ---------- 能力边界（全页唯一反相区块） ---------- */
.page-about .about-limits__panel {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-radius: var(--radius-lg);
  padding: var(--space-6) var(--space-3);
}

.page-about .about-limits__eyebrow {
  color: var(--color-contrast-accent);
}

.page-about .about-limits__title {
  margin: var(--space-2) 0 var(--space-3);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-contrast-ink);
  max-width: 22ch;
}

.page-about .about-limits__lead {
  margin: 0 0 var(--space-4);
  max-width: 62ch;
  font-size: var(--text-base);
  line-height: 1.7;
  color: color-mix(in srgb, var(--color-contrast-ink) 76%, var(--color-contrast-surface));
}

.page-about .about-limits__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
}

.page-about .about-limits__item {
  border-top: var(--border-thin) solid var(--color-contrast-line);
}

.page-about .about-limits__summary {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  padding-block: var(--space-2);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  color: var(--color-contrast-ink);
  cursor: pointer;
  list-style: none;
}

.page-about .about-limits__summary::-webkit-details-marker {
  display: none;
}

.page-about .about-limits__summary::after {
  content: "+";
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: var(--text-base);
  color: var(--color-contrast-accent);
}

.page-about .about-limits__item[open] .about-limits__summary::after {
  content: "–";
}

.page-about .about-limits__num {
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-contrast-accent);
}

.page-about .about-limits__body {
  margin: 0;
  padding-bottom: var(--space-3);
  max-width: 58ch;
  font-size: var(--text-base);
  line-height: 1.7;
  color: color-mix(in srgb, var(--color-contrast-ink) 82%, var(--color-contrast-surface));
}

/* ---------- 内容口径 ---------- */
.page-about .about-principles {
  margin: var(--space-4) 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 0;
  border-top: var(--border-thin) solid var(--color-line);
}

.page-about .about-principles__item {
  padding-block: var(--space-3);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.page-about .about-principles__tag {
  display: inline-block;
  margin-bottom: var(--space-2);
  padding: 2px var(--space-1);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  color: var(--color-primary);
  background: var(--color-primary-soft);
  border-radius: var(--radius-sm);
}

.page-about .about-principles__name {
  margin: 0 0 var(--space-2);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  color: var(--color-ink);
}

.page-about .about-principles__text {
  margin: 0;
  max-width: var(--measure);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

.page-about .about-chapter__back {
  margin-top: var(--space-4);
  padding-top: var(--space-3);
  border-top: var(--border-thin) solid var(--color-line);
}

/* ---------- 备案信息 ---------- */
.page-about .about-registry__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
}

.page-about .about-registry__title {
  margin: 0 0 var(--space-3);
}

.page-about .about-registry__list {
  margin: 0;
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
  border-top: var(--border-thin) solid var(--color-line);
}

.page-about .about-registry__row {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-1);
  padding-block: var(--space-2);
  border-bottom: var(--border-thin) solid var(--color-line);
}

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

.page-about .about-registry__val {
  margin: 0;
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--color-ink);
  word-break: break-word;
}

/* ---------- 延伸入口 ---------- */
.page-about .about-next__head {
  margin-bottom: var(--space-4);
}

.page-about .about-next__list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-2);
}

.page-about .about-next__link {
  display: grid;
  grid-template-columns: auto 1fr;
  column-gap: var(--space-2);
  row-gap: var(--space-1);
  padding: var(--space-3);
  text-decoration: none;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
  background: color-mix(in srgb, var(--color-surface-deep) 55%, transparent);
  transition: border-color 160ms ease, box-shadow 160ms ease, background 160ms ease;
}

.page-about .about-next__link:hover,
.page-about .about-next__link:focus-visible {
  border-color: var(--about-edge);
  box-shadow: 0 0 22px color-mix(in srgb, var(--color-primary) 24%, transparent);
  background: color-mix(in srgb, var(--color-surface-deep) 80%, transparent);
}

.page-about .about-next__num {
  grid-row: 1 / span 2;
  font-size: var(--text-lg);
  line-height: 1.1;
  color: var(--color-primary);
}

.page-about .about-next__name {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  color: var(--color-ink);
}

.page-about .about-next__desc {
  font-size: var(--text-sm);
  line-height: 1.6;
  color: var(--color-ink-soft);
}

/* ---------- 响应式 ---------- */
@media (min-width: 720px) {
  .page-about .about-scale__item {
    grid-template-columns: minmax(0, 0.75fr) minmax(0, 1.9fr);
    align-items: baseline;
    gap: var(--space-4);
  }

  .page-about .about-registry__row {
    grid-template-columns: minmax(0, 0.8fr) minmax(0, 2fr);
    align-items: baseline;
    gap: var(--space-4);
  }

  .page-about .about-limits__grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    column-gap: var(--space-6);
  }

  .page-about .about-next__list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .page-about .about-limits__panel {
    padding: var(--space-6) var(--space-6);
  }

  .page-about .about-limits__title {
    font-size: var(--text-xl);
  }
}

@media (min-width: 900px) {
  .page-about .about-lead__grid {
    grid-template-columns: minmax(0, 1.5fr) minmax(0, 0.85fr);
    gap: var(--space-8);
    align-items: start;
  }

  .page-about .about-lead__title {
    font-size: var(--text-2xl);
  }

  .page-about .about-chapter__grid {
    grid-template-columns: var(--about-rail) minmax(0, 1fr);
    gap: var(--space-6);
  }

  .page-about .about-chapter__aside {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-1);
    position: sticky;
    top: var(--space-6);
  }

  .page-about .about-chapter__title {
    font-size: var(--text-xl);
  }

  .page-about .about-registry__grid {
    grid-template-columns: minmax(0, 0.85fr) minmax(0, 1.6fr);
    gap: var(--space-6);
    align-items: start;
  }

  .page-about .about-next__list {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-toc__link,
  .page-about .about-chapter__link,
  .page-about .about-next__link {
    transition: none;
  }
}