.page-about {
  background: var(--paper);
  color: var(--ink);
  --ab-hero-pad: calc(var(--header-h) + 72px);
}

/* ---------- 首屏 ---------- */
.page-about .ab-hero {
  position: relative;
  overflow: hidden;
  background: var(--ink);
  color: var(--paper);
  padding: var(--ab-hero-pad) 0 56px;
}

.page-about .ab-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(220, 232, 244, .07) 1px, transparent 1px),
    linear-gradient(90deg, rgba(220, 232, 244, .07) 1px, transparent 1px);
  background-size: 68px 68px;
  -webkit-mask-image: radial-gradient(circle at 72% 26%, #000 0%, transparent 70%);
  mask-image: radial-gradient(circle at 72% 26%, #000 0%, transparent 70%);
  pointer-events: none;
}

.page-about .ab-hero__ghost {
  position: absolute;
  right: -0.06em;
  bottom: -0.3em;
  font-size: clamp(9rem, 32vw, 24rem);
  font-weight: 200;
  line-height: .78;
  letter-spacing: -.05em;
  color: rgba(247, 244, 238, .055);
  pointer-events: none;
  user-select: none;
}

.page-about .ab-hero__inner {
  position: relative;
  z-index: 1;
}

.page-about .ab-hero__crumb {
  margin: 0 0 26px;
  font-size: 13px;
  letter-spacing: .06em;
  color: var(--on-dark-soft);
}
.page-about .ab-hero__crumb a {
  color: var(--on-dark);
  text-decoration: none;
  border-bottom: 1px solid rgba(247, 244, 238, .35);
  transition: color .18s var(--ease), border-color .18s var(--ease);
}
.page-about .ab-hero__crumb a:hover,
.page-about .ab-hero__crumb a:focus-visible {
  color: var(--orange);
  border-bottom-color: var(--orange);
}
.page-about .ab-hero__crumb span[aria-hidden] {
  margin: 0 8px;
  color: var(--on-dark-soft);
}

.page-about .ab-hero__eyebrow {
  margin: 0;
  color: var(--orange);
  letter-spacing: .22em;
}

.page-about .ab-hero__title {
  margin: 18px 0 0;
  max-width: 22ch;
  font-size: clamp(1.85rem, 6vw, 4.2rem);
  font-weight: 200;
  line-height: 1.06;
  letter-spacing: -.02em;
  color: var(--paper);
}

.page-about .ab-hero__lede {
  margin: 26px 0 0;
  max-width: 40rem;
  font-size: 17px;
  line-height: 1.85;
  color: var(--on-dark);
}

.page-about .ab-hero__stats {
  list-style: none;
  margin: 44px 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  border-top: 1px solid rgba(247, 244, 238, .2);
  border-left: 1px solid rgba(247, 244, 238, .2);
}
.page-about .ab-hero__stats li {
  padding: 18px 16px 20px;
  border-right: 1px solid rgba(247, 244, 238, .2);
  border-bottom: 1px solid rgba(247, 244, 238, .2);
}
.page-about .ab-stat__num {
  display: block;
  font-size: clamp(1.5rem, 4.4vw, 2.2rem);
  font-weight: 300;
  line-height: 1.1;
  letter-spacing: -.01em;
  color: var(--orange);
  font-variant-numeric: tabular-nums;
}
.page-about .ab-stat__plus {
  font-size: .62em;
  vertical-align: super;
  margin-left: 1px;
}
.page-about .ab-stat__label {
  display: block;
  margin-top: 8px;
  font-size: 13px;
  line-height: 1.6;
  letter-spacing: .06em;
  color: var(--on-dark-soft);
}

/* ---------- 主体两栏 ---------- */
.page-about .ab-body {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 0;
  padding-top: 40px;
  padding-bottom: 72px;
}

.page-about .ab-rail {
  border-bottom: 1px solid var(--line-strong);
  padding-bottom: 24px;
  margin-bottom: 8px;
}
.page-about .ab-rail__nav {
  margin: 0;
}
.page-about .ab-rail__title {
  margin: 0 0 14px;
  font-size: 12px;
  letter-spacing: .2em;
  text-transform: uppercase;
  color: var(--slate);
}
.page-about .ab-rail__list {
  list-style: none;
  margin: 0;
  padding: 0;
}
.page-about .ab-rail__item {
  border-top: 1px solid var(--line);
}
.page-about .ab-rail__link {
  display: flex;
  align-items: baseline;
  gap: 12px;
  padding: 11px 6px 11px 2px;
  color: var(--ink);
  font-size: 14px;
  text-decoration: none;
  transition: color .18s var(--ease), background-color .18s var(--ease), padding-left .18s var(--ease);
}
.page-about .ab-rail__num {
  flex: none;
  font-size: 11px;
  letter-spacing: .16em;
  color: var(--slate);
  font-variant-numeric: tabular-nums;
  transition: color .18s var(--ease);
}
.page-about .ab-rail__link:hover,
.page-about .ab-rail__link:focus-visible {
  background: var(--ink);
  color: var(--paper);
  padding-left: 10px;
}
.page-about .ab-rail__link:hover .ab-rail__num,
.page-about .ab-rail__link:focus-visible .ab-rail__num {
  color: var(--orange);
}
.page-about .ab-rail__link[aria-current="true"] {
  color: var(--brand);
  font-weight: 700;
}
.page-about .ab-rail__link[aria-current="true"] .ab-rail__num {
  color: var(--orange);
  font-weight: 700;
}
.page-about .ab-rail__note {
  margin: 20px 0 0;
  font-size: 13px;
  line-height: 1.7;
  color: var(--slate);
}
.page-about .ab-rail__note a {
  color: var(--brand);
  text-decoration: none;
  border-bottom: 1px solid var(--line-strong);
}
.page-about .ab-rail__note a:hover {
  color: var(--orange);
  border-bottom-color: var(--orange);
}

/* ---------- 章节 ---------- */
.page-about .ab-sec {
  position: relative;
  padding: 48px 0 10px;
  scroll-margin-top: calc(var(--header-h) + 20px);
}
.page-about .ab-sec::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 5px;
  border-top: 1px solid var(--line-strong);
  border-bottom: 1px solid var(--line);
}
.page-about .ab-sec:first-child {
  padding-top: 40px;
}
.page-about .ab-sec:first-child::before {
  display: none;
}

.page-about .ab-sec__title {
  display: flex;
  align-items: baseline;
  gap: 16px;
  margin: 0 0 24px;
  font-size: clamp(1.3rem, 3.6vw, 1.9rem);
  font-weight: 700;
  line-height: 1.32;
  letter-spacing: -.01em;
  color: var(--ink);
}
.page-about .ab-sec__no {
  flex: none;
  font-size: 12px;
  letter-spacing: .2em;
  color: var(--orange);
  font-variant-numeric: tabular-nums;
}

.page-about .ab-prose {
  max-width: 34em;
  font-size: 17px;
  line-height: 1.85;
  color: var(--ink);
}
.page-about .ab-prose p {
  margin: 0 0 20px;
}
.page-about .ab-prose p:last-child {
  margin-bottom: 0;
}
.page-about .ab-prose a {
  color: var(--brand);
  text-decoration: none;
  border-bottom: 1px solid var(--line-strong);
  transition: color .18s var(--ease), border-color .18s var(--ease);
}
.page-about .ab-prose a:hover,
.page-about .ab-prose a:focus-visible {
  color: var(--orange);
  border-bottom-color: var(--orange);
}

.page-about .ab-quote {
  margin: 32px 0 0;
  max-width: 36em;
  padding: 22px 24px;
  background: var(--sky);
  border-left: 3px solid var(--orange);
  font-size: 16px;
  line-height: 1.8;
  color: var(--ink);
}

.page-about .ab-sec__note {
  margin: 22px 0 0;
  max-width: 40em;
}
.page-about .ab-sec__note a {
  color: var(--brand);
  text-decoration: none;
  border-bottom: 1px solid var(--line-strong);
}
.page-about .ab-sec__note a:hover,
.page-about .ab-sec__note a:focus-visible {
  color: var(--orange);
  border-bottom-color: var(--orange);
}
.page-about .ab-sec__note--end {
  margin-top: 32px;
}

/* ---------- 图文分栏 ---------- */
.page-about .ab-split {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 30px;
  align-items: start;
}

.page-about .ab-split__media {
  margin: 0;
}
.page-about .ab-split__media img {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--line-strong);
  background: var(--panel);
  object-fit: cover;
}
.page-about .ab-split__media .annotation {
  display: block;
  margin-top: 12px;
}

.page-about .ab-figure {
  margin: 0 0 34px;
}
.page-about .ab-figure img {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--line-strong);
  background: var(--panel);
}
.page-about .ab-figure .annotation {
  display: block;
  margin-top: 12px;
}

/* ---------- 小组分工 ---------- */
.page-about .ab-role {
  list-style: none;
  margin: 26px 0 26px;
  padding: 0;
}
.page-about .ab-role__item {
  padding: 16px 0 16px 18px;
  margin-bottom: 12px;
  border-left: 2px solid var(--sky);
  transition: border-color .18s var(--ease);
}
.page-about .ab-role__item:hover {
  border-left-color: var(--orange);
}
.page-about .ab-role__name {
  margin: 0 0 6px;
  font-size: 16px;
  font-weight: 700;
  line-height: 1.4;
  color: var(--ink);
}
.page-about .ab-role__desc {
  margin: 0;
  max-width: 34em;
  font-size: 15px;
  line-height: 1.8;
  color: var(--slate);
}

/* ---------- 更新节奏 ---------- */
.page-about .ab-cadence {
  list-style: none;
  margin: 30px 0 0;
  padding: 0;
  border-top: 1px solid var(--line-strong);
  max-width: 44em;
}
.page-about .ab-cadence li {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 6px;
  padding: 16px 0;
  border-bottom: 1px solid var(--line);
}
.page-about .ab-cadence__k {
  font-size: 12px;
  letter-spacing: .18em;
  font-weight: 700;
  color: var(--orange);
}
.page-about .ab-cadence__v {
  font-size: 15px;
  line-height: 1.8;
  color: var(--ink);
}

/* ---------- 条目三段结构 ---------- */
.page-about .ab-struct {
  list-style: none;
  margin: 26px 0 26px;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 12px;
}
.page-about .ab-struct__item {
  padding: 18px 20px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-top: 2px solid var(--brand);
  transition: border-top-color .18s var(--ease);
}
.page-about .ab-struct__item:hover {
  border-top-color: var(--orange);
}
.page-about .ab-struct__k {
  display: block;
  margin-bottom: 8px;
  font-size: 12px;
  letter-spacing: .18em;
  font-weight: 700;
  color: var(--brand);
}
.page-about .ab-struct__v {
  margin: 0;
  font-size: 15px;
  line-height: 1.8;
  color: var(--ink);
}

/* ---------- 年份节点 ---------- */
.page-about .ab-timeline {
  list-style: none;
  margin: 0;
  padding: 0 0 0 24px;
  border-left: 1px solid var(--line-strong);
}
.page-about .ab-timeline__item {
  position: relative;
  padding-bottom: 30px;
}
.page-about .ab-timeline__item::before {
  content: "";
  position: absolute;
  left: -29px;
  top: 7px;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--press);
  box-shadow: 0 0 0 3px var(--paper), 0 0 0 4px var(--line-strong);
}
.page-about .ab-timeline__item:last-child {
  padding-bottom: 8px;
}
.page-about .ab-timeline__year {
  display: inline-block;
  font-size: 12px;
  letter-spacing: .2em;
  font-weight: 700;
  color: var(--slate);
  font-variant-numeric: tabular-nums;
}
.page-about .ab-timeline__title {
  margin: 8px 0 12px;
  font-size: 18px;
  font-weight: 700;
  line-height: 1.4;
  color: var(--ink);
}

/* ---------- 折叠面板 ---------- */
.page-about .ab-fold__trigger {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 12px 14px;
  background: var(--sky);
  border: 1px solid var(--line);
  border-left: 3px solid var(--brand);
  color: var(--ink);
  font-family: inherit;
  font-size: 14px;
  cursor: pointer;
  text-align: left;
  transition: background-color .18s var(--ease), border-left-color .18s var(--ease);
}
.page-about .ab-fold__trigger:hover,
.page-about .ab-fold__trigger:focus-visible {
  background: var(--panel);
  border-left-color: var(--orange);
}
.page-about .ab-fold__label {
  flex: 1 1 auto;
}
.page-about .ab-fold__sign {
  position: relative;
  flex: none;
  width: 12px;
  height: 12px;
}
.page-about .ab-fold__sign::before,
.page-about .ab-fold__sign::after {
  content: "";
  position: absolute;
  background: var(--brand);
  transition: transform .2s var(--ease);
}
.page-about .ab-fold__sign::before {
  left: 0;
  top: 5px;
  width: 12px;
  height: 2px;
}
.page-about .ab-fold__sign::after {
  top: 0;
  left: 5px;
  width: 2px;
  height: 12px;
}
.page-about .fold.is-open .ab-fold__sign::after,
.page-about .fold[data-open] .ab-fold__sign::after {
  transform: scaleY(0);
}

.page-about .ab-fold__text {
  margin: 0;
  max-width: 36em;
  font-size: 15px;
  line-height: 1.85;
  color: var(--slate);
}
.page-about .ab-fold__text a {
  color: var(--brand);
  text-decoration: none;
  border-bottom: 1px solid var(--line-strong);
}
.page-about .ab-fold__text a:hover {
  color: var(--orange);
  border-bottom-color: var(--orange);
}
.page-about .fold__body-inner {
  padding-top: 14px;
}

/* ---------- 响应式 ---------- */
@media (min-width: 640px) {
  .page-about .ab-hero__stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
  .page-about .ab-cadence li {
    grid-template-columns: 150px minmax(0, 1fr);
    gap: 24px;
    align-items: baseline;
  }
  .page-about .ab-struct {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (min-width: 900px) {
  .page-about {
    --ab-hero-pad: calc(var(--header-h) + 104px);
  }
  .page-about .ab-hero {
    padding-bottom: 76px;
  }
  .page-about .ab-body {
    grid-template-columns: 216px minmax(0, 1fr);
    column-gap: 56px;
    padding-top: 72px;
    padding-bottom: 104px;
  }
  .page-about .ab-rail {
    position: sticky;
    top: calc(var(--header-h) + 32px);
    align-self: start;
    border-bottom: 0;
    padding-bottom: 0;
    margin-bottom: 0;
    max-height: calc(100vh - var(--header-h) - 56px);
    overflow-y: auto;
  }
  .page-about .ab-sec {
    padding: 64px 0 16px;
  }
  .page-about .ab-sec:first-child {
    padding-top: 0;
  }
  .page-about .ab-sec:first-child::before {
    display: block;
  }
  .page-about .ab-split {
    grid-template-columns: minmax(0, 1.15fr) minmax(0, .85fr);
    gap: 48px;
  }
  .page-about .ab-split--flip {
    grid-template-columns: minmax(0, 1.05fr) minmax(0, .95fr);
  }
  .page-about .ab-figure {
    margin-bottom: 40px;
  }
}

@media (min-width: 1180px) {
  .page-about .ab-body {
    grid-template-columns: 240px minmax(0, 1fr);
    column-gap: 72px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .ab-rail__link,
  .page-about .ab-role__item,
  .page-about .ab-struct__item,
  .page-about .ab-fold__trigger,
  .page-about .ab-fold__sign::after {
    transition: none;
  }
  .page-about .ab-rail__link:hover,
  .page-about .ab-rail__link:focus-visible {
    padding-left: 6px;
  }
}
</main>