.page-about {
  background: var(--color-surface);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: var(--leading-body);
}

/* ---------- 首屏文字区 ---------- */
.page-about .about-head {
  padding: var(--space-6) 0 var(--space-6);
}

.page-about .about-head .breadcrumbs {
  margin-bottom: var(--space-3);
}

.page-about .about-head .eyebrow {
  color: var(--color-primary);
  margin: 0;
}

.page-about .about-title {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: clamp(var(--text-xl), 5.4vw, var(--text-4xl));
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
  max-width: 22ch;
  margin: var(--space-3) 0 var(--space-4);
}

.page-about .about-lede {
  max-width: var(--measure);
  color: var(--color-ink-soft);
  font-size: var(--text-lg);
  line-height: 1.5;
  margin: 0;
}

.page-about .about-lede strong {
  color: var(--color-ink);
  font-weight: var(--weight-heading);
}

.page-about .about-facts {
  margin: var(--space-6) 0 0;
  max-width: var(--measure);
}

.page-about .about-facts__row {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-1) var(--space-3);
  padding: var(--space-2) 0;
  border-bottom: 1px dotted var(--color-line);
}

.page-about .about-facts__row dt {
  flex: 0 0 auto;
  min-width: 7em;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-ink-muted);
}

.page-about .about-facts__row dd {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-ink);
}

/* ---------- 主体骨架 ---------- */
.page-about .about-shell {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-6);
  padding-bottom: var(--space-6);
}

@media (min-width: 900px) {
  .page-about .about-shell {
    grid-template-columns: minmax(0, 186px) minmax(0, 1fr);
    column-gap: var(--space-8);
    align-items: start;
  }
}

/* ---------- 左侧目录 ---------- */
.page-about .about-rail {
  min-width: 0;
}

@media (min-width: 900px) {
  .page-about .about-rail {
    position: sticky;
    top: 96px;
  }
}

.page-about .about-rail__title {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  margin: 0 0 var(--space-2);
}

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

.page-about .about-rail__list a {
  display: flex;
  align-items: center;
  min-height: 44px;
  padding: 0 var(--space-3);
  border-radius: var(--radius-pill);
  background: var(--color-surface-alt);
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  text-decoration: none;
  transition: background-color 160ms ease, color 160ms ease;
}

.page-about .about-rail__list a:hover,
.page-about .about-rail__list a:focus-visible {
  background: var(--color-primary);
  color: var(--color-primary-ink);
  outline: none;
}

.page-about .about-rail__list a:focus-visible {
  box-shadow: var(--shadow-1);
}

/* ---------- 叙事流 ---------- */
.page-about .about-story {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
  min-width: 0;
}

.page-about .about-block {
  position: relative;
  padding-left: var(--space-4);
  scroll-margin-top: 104px;
}

.page-about .about-block::before {
  content: "";
  position: absolute;
  left: 0;
  top: var(--space-1);
  bottom: var(--space-1);
  width: var(--border-thick);
  background: var(--color-primary);
  transition: width 160ms ease, background-color 160ms ease;
}

.page-about .about-block:has(.about-tag:hover)::before,
.page-about .about-block:has(.about-tag:focus-visible)::before {
  width: calc(var(--border-thick) * 2);
}

.page-about .about-tag {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  margin: 0 0 var(--space-2);
}

.page-about .about-h2 {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: clamp(var(--text-lg), 3.4vw, var(--text-2xl));
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
  margin: 0 0 var(--space-3);
  max-width: 24ch;
}

.page-about .about-prose p {
  max-width: var(--measure);
  margin: 0 0 var(--space-3);
  font-size: var(--text-base);
  color: var(--color-ink-soft);
}

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

.page-about .about-prose strong {
  color: var(--color-ink);
  font-weight: var(--weight-heading);
}

.page-about .about-prose a {
  color: var(--color-primary);
  text-decoration: underline;
  text-underline-offset: 4px;
  text-decoration-thickness: 1px;
  transition: color 160ms ease, text-decoration-color 160ms ease;
}

.page-about .about-prose a:hover,
.page-about .about-prose a:focus-visible {
  color: var(--color-accent);
  text-decoration-color: var(--color-accent);
}

.page-about .about-mark {
  background: var(--color-highlight);
  color: var(--color-ink);
  font-weight: var(--weight-heading);
  padding: 0 0.2em;
  -webkit-box-decoration-break: clone;
  box-decoration-break: clone;
}

.page-about .about-tip {
  font-family: var(--font-mono);
  color: var(--color-ink);
  border-bottom: 1px dotted var(--color-ink-muted);
  cursor: help;
}

/* ---------- 首段两栏错位 ---------- */
.page-about .about-split {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-4);
}

@media (min-width: 760px) {
  .page-about .about-split {
    grid-template-columns: minmax(0, 1.55fr) minmax(0, 1fr);
    column-gap: var(--space-6);
    align-items: start;
  }
}

/* ---------- 图片协议 ---------- */
.page-about .about-figure {
  margin: 0;
  min-width: 0;
}

.page-about .about-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  background: var(--color-surface-deep);
}

.page-about .about-figure figcaption {
  margin-top: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  line-height: 1.7;
  color: var(--color-ink-muted);
  max-width: 48ch;
}

.page-about .about-figure--tall img {
  aspect-ratio: 4 / 5;
}

.page-about .about-figure--wide {
  margin: var(--space-2) 0 0;
}

.page-about .about-figure--wide img {
  aspect-ratio: 16 / 7;
}

.page-about .about-figure--square img {
  aspect-ratio: 4 / 3;
}

/* ---------- 阶段条目 ---------- */
.page-about .about-stages {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.page-about .about-stage {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-1);
  padding-top: var(--space-3);
  border-top: 1px dotted var(--color-line);
  transition: border-color 160ms ease;
}

.page-about .about-stage:hover {
  border-top-color: var(--color-primary);
}

.page-about .about-stage__num {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  color: var(--color-ink-muted);
  margin: 0;
  transition: color 160ms ease;
}

.page-about .about-stage:hover .about-stage__num {
  color: var(--color-accent);
}

.page-about .about-stage__title {
  font-family: var(--font-heading);
  font-size: var(--text-base);
  font-weight: var(--weight-heading);
  color: var(--color-ink);
  margin: 0 0 var(--space-1);
  line-height: var(--leading-heading);
}

.page-about .about-stage__body {
  margin: 0;
  font-size: var(--text-sm);
  line-height: 1.75;
  color: var(--color-ink-soft);
  max-width: 62ch;
}

@media (min-width: 760px) {
  .page-about .about-stage {
    grid-template-columns: minmax(0, 118px) minmax(0, 1fr);
    column-gap: var(--space-4);
    align-items: start;
  }
}

/* ---------- 反色停顿带 ---------- */
.page-about .about-band {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  padding: var(--space-4);
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: var(--space-3);
}

@media (min-width: 760px) {
  .page-about .about-band {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-6);
    padding: var(--space-6);
  }
}

.page-about .about-band__label {
  margin: 0;
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-contrast-accent);
}

.page-about .about-band__text {
  margin: 0;
  flex: 1 1 auto;
  max-width: 52ch;
  font-size: var(--text-base);
  line-height: 1.7;
  color: var(--color-contrast-ink);
}

.page-about .about-band .pill--contrast {
  flex: 0 0 auto;
  min-height: 44px;
  display: inline-flex;
  align-items: center;
}

/* ---------- 能力与边界 ---------- */
.page-about .about-limits {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-6);
}

@media (min-width: 760px) {
  .page-about .about-limits {
    grid-template-columns: minmax(0, 1.3fr) minmax(0, 1fr);
    column-gap: var(--space-6);
    align-items: start;
  }
}

.page-about .about-limits__head {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  margin: 0 0 var(--space-3);
  padding-bottom: var(--space-2);
  border-bottom: 1px dotted var(--color-line);
}

.page-about .about-limits__col--in .about-limits__head {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.page-about .about-limits__col--out .about-limits__head {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
}

.page-about .about-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .about-list li {
  position: relative;
  padding: var(--space-2) 0 var(--space-2) var(--space-3);
  border-bottom: 1px dotted var(--color-line);
  font-size: var(--text-sm);
  line-height: 1.7;
  color: var(--color-ink);
}

.page-about .about-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: calc(var(--space-2) + 0.62em);
  width: 6px;
  height: 6px;
  border-radius: var(--radius-pill);
  background: var(--color-primary);
}

.page-about .about-list--mute li {
  color: var(--color-ink-muted);
}

.page-about .about-list--mute li::before {
  background: var(--color-accent);
}

/* ---------- 归档步骤 ---------- */
.page-about .about-steps {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .about-step {
  display: grid;
  grid-template-columns: minmax(0, 52px) minmax(0, 1fr);
  column-gap: var(--space-3);
  align-items: start;
  padding: var(--space-3) 0;
  border-bottom: 1px dotted var(--color-line);
  transition: border-color 160ms ease;
}

.page-about .about-step:first-child {
  border-top: 1px dotted var(--color-line);
}

.page-about .about-step:hover {
  border-bottom-color: var(--color-primary);
}

.page-about .about-step__num {
  font-family: var(--font-mono);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  line-height: 1.05;
  color: var(--color-primary);
  transition: color 160ms ease;
}

.page-about .about-step:hover .about-step__num {
  color: var(--color-accent);
}

.page-about .about-step__title {
  font-family: var(--font-heading);
  font-size: var(--text-base);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  color: var(--color-ink);
  margin: 0 0 var(--space-1);
}

.page-about .about-step__body {
  margin: 0;
  max-width: 58ch;
  font-size: var(--text-sm);
  line-height: 1.75;
  color: var(--color-ink-soft);
}

.page-about .about-step__body a {
  color: var(--color-primary);
  text-decoration: underline;
  text-underline-offset: 4px;
}

.page-about .about-step__body a:hover,
.page-about .about-step__body a:focus-visible {
  color: var(--color-accent);
}

/* ---------- 运营立场 ---------- */
.page-about .about-principles {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-4);
}

@media (min-width: 760px) {
  .page-about .about-principles {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1.45fr);
    column-gap: var(--space-6);
    align-items: start;
  }
}

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

/* ---------- 结尾 ---------- */
.page-about .about-tail {
  padding-bottom: var(--space-8);
}

.page-about .about-tail .rule {
  margin-bottom: var(--space-4);
}

.page-about .about-tail__lead {
  max-width: var(--measure);
  margin: 0 0 var(--space-4);
  font-size: var(--text-base);
  color: var(--color-ink-soft);
}

.page-about .about-tail .pill-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.page-about .about-tail .pill {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
}

@media (max-width: 640px) {
  .page-about .about-block {
    padding-left: var(--space-3);
  }

  .page-about .about-tag,
  .page-about .about-stage__num,
  .page-about .about-facts__row dt {
    letter-spacing: 0.1em;
  }

  .page-about .about-figure--tall img {
    aspect-ratio: 1 / 1;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-block::before,
  .page-about .about-rail__list a,
  .page-about .about-stage,
  .page-about .about-stage__num,
  .page-about .about-step,
  .page-about .about-step__num {
    transition: none;
  }
}