.page-about {
  --pa-rail-gap: clamp(24px, 3vw, 44px);
}

/* ---------- 面包屑 ---------- */
.page-about .breadcrumb {
  padding-top: clamp(18px, 3.2vw, 36px);
  padding-bottom: clamp(10px, 2vw, 18px);
}
.page-about .breadcrumb a {
  color: var(--c-mid);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}
.page-about .breadcrumb a:hover,
.page-about .breadcrumb a:focus-visible {
  color: var(--c-red);
  border-bottom-color: var(--c-red);
}

/* ---------- 首屏 ---------- */
.page-about .pa-hero {
  padding-bottom: clamp(28px, 5vw, 52px);
}
.page-about .pa-hero__grid {
  align-items: end;
  row-gap: clamp(26px, 4vw, 44px);
}
.page-about .pa-hero__title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(34px, 5.4vw, 66px);
  line-height: 1.08;
  letter-spacing: -0.015em;
  color: var(--c-ink);
  margin: 14px 0 0;
  max-width: 14em;
}
.page-about .pa-hero__lede {
  margin-top: 22px;
  max-width: 36em;
  font-size: 16px;
  line-height: 1.85;
}
.page-about .pa-hero__note {
  margin-top: 18px;
  max-width: 30em;
}
.page-about .pa-hero__figure {
  margin: 0;
}
.page-about .pa-hero__figure .figure-frame {
  margin: 0;
}
.page-about .pa-hero__figure img {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 5 / 3;
  object-fit: cover;
}

/* ---------- 数据条 ---------- */
.page-about .pa-facts {
  list-style: none;
  margin: clamp(34px, 5vw, 58px) 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  background: var(--c-line);
  border-top: 2px solid var(--c-gold);
  border-bottom: 1px solid var(--c-line);
}
.page-about .pa-facts__item {
  background: var(--c-paper);
  padding: 18px 20px 20px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  min-width: 0;
}
.page-about .pa-facts__num {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(24px, 3vw, 34px);
  line-height: 1;
  color: var(--c-red);
  letter-spacing: -0.01em;
}
.page-about .pa-facts__label {
  font-size: 13px;
  line-height: 1.5;
  color: var(--c-mid);
  letter-spacing: 0.02em;
}

/* ---------- 主体两栏 ---------- */
.page-about .pa-body {
  padding-top: clamp(38px, 6vw, 76px);
  padding-bottom: clamp(48px, 7vw, 96px);
}
.page-about .pa-rail {
  position: relative;
}
.page-about .pa-rail__inner {
  position: sticky;
  top: calc(var(--header-h) + 26px);
}
.page-about .pa-rail__title {
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  color: var(--c-gold);
}
.page-about .pa-rail__inner .index-rail__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 1px;
  border-top: 1px solid var(--c-line);
}
.page-about .pa-rail__inner .index-rail__item {
  margin: 0;
}
.page-about .index-rail__link {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 11px 12px 11px 14px;
  border-left: 2px solid transparent;
  color: var(--c-mid);
  text-decoration: none;
  font-size: 14px;
  line-height: 1.45;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease), background-color var(--dur) var(--ease);
}
.page-about .index-rail__link .mono {
  font-size: 11.5px;
  color: var(--c-gold);
  letter-spacing: 0.06em;
}
.page-about .index-rail__link:hover,
.page-about .index-rail__link:focus-visible {
  color: var(--c-ink);
  background: var(--c-paper);
  border-left-color: var(--c-gold);
}
.page-about .index-rail__link.is-active {
  color: var(--c-red);
  background: var(--c-paper);
  border-left-color: var(--c-red);
}
.page-about .index-rail__link.is-active .mono {
  color: var(--c-red);
}
.page-about .pa-rail__foot {
  margin: 20px 0 0;
  padding-top: 16px;
  border-top: 1px solid var(--c-line);
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.85;
  color: var(--c-mid);
}

/* ---------- 章节 ---------- */
.page-about .pa-sec {
  scroll-margin-top: calc(var(--header-h) + 24px);
}
.page-about .pa-sec__head {
  margin-bottom: clamp(18px, 3vw, 28px);
}
.page-about .eyebrow {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 12.5px;
  letter-spacing: 0.12em;
  color: var(--c-red);
  margin: 0;
}
.page-about .eyebrow .mono {
  color: var(--c-gold);
  margin-right: 6px;
  font-size: 12.5px;
}
.page-about .section-title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(26px, 3.4vw, 42px);
  line-height: 1.22;
  letter-spacing: -0.01em;
  color: var(--c-ink);
  margin: 10px 0 0;
}
.page-about .pa-sec__sum {
  margin: 12px 0 0;
  padding-left: 14px;
  border-left: 2px solid var(--c-gold);
  color: var(--c-mid);
  font-size: 15px;
  line-height: 1.7;
  max-width: 34em;
}
.page-about .pa-article .prose {
  max-width: 42em;
}
.page-about .pa-article .prose p {
  margin: 0 0 1.15em;
}
.page-about .pa-article .prose p:last-child {
  margin-bottom: 0;
}
.page-about .pa-article .prose a {
  color: var(--c-red);
  text-decoration: none;
  border-bottom: 1px solid var(--c-line);
  transition: border-color var(--dur) var(--ease), color var(--dur) var(--ease);
}
.page-about .pa-article .prose a:hover,
.page-about .pa-article .prose a:focus-visible {
  border-bottom-color: var(--c-red);
}
.page-about .pa-article .prose .mono {
  font-size: 13.5px;
  color: var(--c-ink);
  background: var(--c-paper);
  border: 1px solid var(--c-line);
  padding: 1px 6px;
  white-space: nowrap;
}

/* ---------- 结构图 ---------- */
.page-about .pa-tree {
  list-style: none;
  margin: clamp(26px, 4vw, 40px) 0;
  padding: 0 0 0 24px;
  position: relative;
  display: grid;
  gap: 12px;
}
.page-about .pa-tree::before {
  content: "";
  position: absolute;
  left: 6px;
  top: 10px;
  bottom: 10px;
  width: 1px;
  background: linear-gradient(180deg, var(--c-red) 0%, var(--c-gold) 55%, var(--c-line) 100%);
}
.page-about .pa-tree__group {
  position: relative;
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 16px;
  align-items: start;
  padding: 16px 18px 18px;
  background: var(--c-paper);
  border: 1px solid var(--c-line);
  transition: border-color var(--dur) var(--ease), background-color var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}
.page-about .pa-tree__group::before {
  content: "";
  position: absolute;
  left: -18px;
  top: 28px;
  width: 18px;
  height: 1px;
  background: var(--c-line);
}
.page-about .pa-tree__group::after {
  content: "";
  position: absolute;
  left: -22px;
  top: 25px;
  width: 7px;
  height: 7px;
  background: var(--c-bg);
  border: 1px solid var(--c-red);
  transform: rotate(45deg);
}
.page-about .pa-tree__group:hover,
.page-about .pa-tree__group:focus-within {
  border-color: var(--c-gold);
  box-shadow: inset 3px 0 0 var(--c-gold);
}
.page-about .pa-tree__group:hover::after,
.page-about .pa-tree__group:focus-within::after {
  background: var(--c-gold);
  border-color: var(--c-gold);
}
.page-about .pa-tree__range {
  align-self: start;
  font-size: 11.5px;
  line-height: 1.6;
  color: var(--c-red);
  border: 1px solid currentColor;
  padding: 2px 7px;
  white-space: nowrap;
}
.page-about .pa-tree__body {
  min-width: 0;
}
.page-about .pa-tree__name {
  margin: 0;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 16px;
  color: var(--c-ink);
}
.page-about .pa-tree__items {
  margin: 6px 0 0;
  font-size: 14px;
  line-height: 1.7;
  color: var(--c-mid);
}
.page-about .pa-tree__desc {
  margin: 8px 0 0;
  font-size: 13.5px;
  line-height: 1.7;
  color: var(--c-mid);
  padding-top: 8px;
  border-top: 1px dashed var(--c-line);
}

/* ---------- 引文块 ---------- */
.page-about .pa-quote {
  margin: clamp(28px, 4vw, 44px) 0;
  background: var(--c-paper);
  border: 1px solid var(--c-line);
  border-left: 3px solid var(--c-gold);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - var(--cut-sm)), calc(100% - var(--cut-sm)) 100%, 0 100%);
  max-width: 42em;
}
.page-about .pa-quote__summary {
  list-style: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 18px 24px;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 15px;
  color: var(--c-ink);
}
.page-about .pa-quote__summary::-webkit-details-marker {
  display: none;
}
.page-about .pa-quote__summary::before {
  content: "+";
  font-family: var(--font-mono);
  font-size: 17px;
  line-height: 1;
  color: var(--c-gold);
}
.page-about .pa-quote[open] .pa-quote__summary::before {
  content: "–";
}
.page-about .pa-quote__summary:focus-visible {
  outline: 2px solid var(--c-teal);
  outline-offset: -4px;
}
.page-about .pa-quote p {
  margin: 0;
  padding: 0 24px 22px;
  font-size: 15px;
  line-height: 1.85;
  color: var(--c-mid);
}

/* ---------- 表格 ---------- */
.page-about .pa-table {
  margin: clamp(24px, 4vw, 36px) 0;
  max-width: 42em;
}
.page-about .pa-table__caption {
  caption-side: top;
  text-align: left;
  padding: 0 0 12px;
  font-size: 13px;
  color: var(--c-mid);
  letter-spacing: 0.02em;
}
.page-about .pa-table th,
.page-about .pa-table td {
  font-size: 13.5px;
}
.page-about .pa-table .mono {
  font-size: 13px;
}

/* ---------- 图片 ---------- */
.page-about .pa-fig {
  margin: clamp(26px, 4vw, 44px) 0 0;
  max-width: 42em;
}
.page-about .pa-fig .figure-frame {
  margin: 0;
}
.page-about .pa-fig img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}

/* ---------- 更新节奏 ---------- */
.page-about .pa-cadence {
  display: grid;
  gap: 14px;
  margin: clamp(24px, 4vw, 36px) 0;
  max-width: 42em;
}
.page-about .pa-cadence__card {
  padding: 22px 22px 24px;
}
.page-about .pa-cadence__card h3 {
  margin: 12px 0 8px;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 17px;
  color: var(--c-ink);
}
.page-about .pa-cadence__card p {
  margin: 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--c-mid);
}

/* ---------- 时间轴 ---------- */
.page-about .timeline {
  list-style: none;
  margin: clamp(24px, 4vw, 40px) 0;
  padding: 0 0 0 28px;
  position: relative;
  max-width: 42em;
}
.page-about .timeline::before {
  content: "";
  position: absolute;
  left: 5px;
  top: 12px;
  bottom: 12px;
  width: 1px;
  background: var(--c-line);
}
.page-about .timeline__item {
  position: relative;
  padding: 0 0 26px;
}
.page-about .timeline__item:last-child {
  padding-bottom: 0;
}
.page-about .timeline__item::before {
  content: "";
  position: absolute;
  left: -27px;
  top: 7px;
  width: 9px;
  height: 9px;
  background: var(--c-bg);
  border: 1px solid var(--c-red);
  transform: rotate(45deg);
}
.page-about .timeline__item:last-child::before {
  background: var(--c-red);
  border-color: var(--c-red);
}
.page-about .timeline__time {
  margin: 0 0 4px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--c-gold);
}
.page-about .pa-timeline__title {
  margin: 0;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 17px;
  color: var(--c-ink);
}
.page-about .pa-timeline__desc {
  margin: 6px 0 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--c-mid);
  max-width: 36em;
}

/* ---------- 继续查阅 ---------- */
.page-about .pa-next {
  margin-top: clamp(40px, 6vw, 74px);
  padding-top: clamp(26px, 4vw, 42px);
  border-top: 2px solid var(--c-red);
}
.page-about .pa-next .section-title {
  font-size: clamp(24px, 3vw, 34px);
}
.page-about .pa-next__grid {
  display: grid;
  gap: 14px;
  margin-top: clamp(20px, 3vw, 30px);
}
.page-about .pa-next__card {
  display: block;
  padding: 20px 20px 24px;
  background: var(--c-paper);
  border: 1px solid var(--c-line);
  border-left: 3px solid var(--c-line);
  text-decoration: none;
  color: var(--c-ink);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - var(--cut-sm)), calc(100% - var(--cut-sm)) 100%, 0 100%);
  transition: border-color var(--dur) var(--ease), border-left-color var(--dur) var(--ease), transform var(--dur) var(--ease);
}
.page-about .pa-next__card:hover,
.page-about .pa-next__card:focus-visible {
  border-color: var(--c-line);
  border-left-color: var(--c-red);
  transform: translateY(-2px);
}
.page-about .pa-next__card .mono {
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--c-gold);
}
.page-about .pa-next__card h3 {
  margin: 10px 0 8px;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 16px;
  color: var(--c-ink);
}
.page-about .pa-next__card p {
  margin: 0;
  font-size: 13.5px;
  line-height: 1.7;
  color: var(--c-mid);
}

/* ---------- 响应式 ---------- */
@media (max-width: 1024px) {
  .page-about .pa-rail__inner {
    position: static;
  }
  .page-about .pa-rail__inner .index-rail__list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0;
  }
  .page-about .index-rail__link {
    border-left: 1px solid transparent;
  }
  .page-about .pa-rail {
    margin-bottom: clamp(28px, 5vw, 44px);
  }
}

@media (min-width: 768px) {
  .page-about .pa-facts {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
  .page-about .pa-cadence {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
  .page-about .pa-next__grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (max-width: 640px) {
  .page-about .pa-rail__inner .index-rail__list {
    grid-template-columns: minmax(0, 1fr);
  }
  .page-about .pa-hero__title {
    font-size: clamp(30px, 8vw, 42px);
  }
  .page-about .pa-tree {
    padding-left: 18px;
  }
  .page-about .pa-tree__group {
    grid-template-columns: minmax(0, 1fr);
    gap: 10px;
    padding: 16px;
  }
  .page-about .pa-tree__group::before {
    left: -14px;
    width: 14px;
  }
  .page-about .pa-tree__group::after {
    left: -18px;
  }
  .page-about .pa-quote__summary,
  .page-about .pa-quote p {
    padding-left: 18px;
    padding-right: 18px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .pa-next__card:hover,
  .page-about .pa-next__card:focus-visible {
    transform: none;
  }
}