.page-about {
  --about-rail: 220px;
  --about-gap: clamp(24px, 4vw, 56px);
  --about-ink-soft: var(--ink-2);
  padding-bottom: clamp(56px, 8vw, 112px);
  color: var(--paper);
  background: var(--ink);
}

.page-about .breadcrumbs {
  padding-top: clamp(24px, 4vw, 48px);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .08em;
  color: var(--mist);
}

.page-about .breadcrumbs a {
  color: var(--mist);
  text-decoration: none;
}

.page-about .breadcrumbs a:hover {
  color: var(--orange-soft);
}

.page-about .breadcrumbs__sep {
  margin: 0 .5em;
  color: var(--line);
}

/* ---------- 首屏：窄栏目录 + 宽声明 ---------- */

.page-about .about-intro {
  padding: clamp(28px, 5vw, 64px) 0 clamp(36px, 6vw, 80px);
}

.page-about .about-intro__grid {
  display: grid;
  gap: var(--about-gap);
}

.page-about .about-intro__aside {
  border-top: 1px solid var(--line);
  padding-top: 18px;
}

.page-about .eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .12em;
  color: var(--jade);
  margin: 0 0 18px;
}

.page-about .about-toc {
  list-style: none;
  margin: 0 0 24px;
  padding: 0;
}

.page-about .about-toc li + li {
  border-top: 1px solid rgba(23, 56, 79, .7);
}

.page-about .about-toc a {
  display: flex;
  align-items: baseline;
  gap: 12px;
  padding: 11px 0;
  color: var(--paper);
  font-size: 15px;
  line-height: 1.4;
  text-decoration: none;
  transition: color var(--dur) var(--ease);
}

.page-about .about-toc a:hover {
  color: var(--orange-soft);
}

.page-about .about-toc__num {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .08em;
  color: var(--orange);
}

.page-about .about-intro__note {
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.7;
  letter-spacing: .04em;
  color: var(--mist);
  margin: 0;
}

.page-about .about-intro__main h1 {
  margin: 0 0 24px;
  font-size: clamp(34px, 6.4vw, 76px);
  font-weight: 900;
  line-height: 1.02;
  letter-spacing: -.03em;
  color: var(--paper);
}

.page-about .about-hl {
  display: block;
  color: var(--orange);
  margin-top: .12em;
}

.page-about .about-intro__lead {
  margin: 0 0 28px;
  max-width: 46ch;
  font-size: clamp(16px, 1.4vw, 19px);
  line-height: 1.78;
  color: var(--mist);
}

.page-about .about-intro__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

/* ---------- 章节折叠 ---------- */

.page-about .chapter {
  border-top: 1px solid var(--line);
  scroll-margin-top: 96px;
}

.page-about .chapter:last-of-type {
  border-bottom: 1px solid var(--line);
}

.page-about .chapter__head {
  display: flex;
  align-items: flex-start;
  gap: 14px;
  padding: clamp(20px, 3vw, 34px) 0;
  cursor: pointer;
  list-style: none;
}

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

.page-about .chapter__head:hover .chapter__title {
  color: var(--orange-soft);
}

.page-about .chapter__num {
  flex: none;
  font-family: var(--font-mono);
  font-size: clamp(14px, 2vw, 18px);
  letter-spacing: .06em;
  color: var(--orange);
  padding-top: .35em;
}

.page-about .chapter__text {
  flex: 1 1 auto;
  min-width: 0;
  display: block;
}

.page-about .chapter__title {
  display: block;
  font-size: clamp(21px, 2.8vw, 34px);
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -.02em;
  color: var(--paper);
  transition: color var(--dur) var(--ease);
}

.page-about .chapter__sub {
  display: block;
  margin-top: 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.6;
  letter-spacing: .04em;
  color: var(--mist);
}

.page-about .chapter__mark {
  flex: none;
  position: relative;
  width: 22px;
  height: 22px;
  margin-top: .4em;
  border: 1px solid var(--line);
  border-radius: 2px;
}

.page-about .chapter__mark::before,
.page-about .chapter__mark::after {
  content: "";
  position: absolute;
  background: var(--jade);
  transition: transform var(--dur) var(--ease), opacity var(--dur) var(--ease);
}

.page-about .chapter__mark::before {
  left: 5px;
  right: 5px;
  top: 50%;
  height: 1px;
  margin-top: -.5px;
}

.page-about .chapter__mark::after {
  top: 5px;
  bottom: 5px;
  left: 50%;
  width: 1px;
  margin-left: -.5px;
}

.page-about .chapter[open] .chapter__mark::after {
  transform: scaleY(0);
  opacity: 0;
}

.page-about .chapter__body {
  display: grid;
  gap: clamp(24px, 3.5vw, 44px);
  padding-bottom: clamp(32px, 5vw, 64px);
}

.page-about .chapter__prose {
  min-width: 0;
}

.page-about .chapter__prose p {
  margin: 0 0 18px;
  font-size: clamp(16px, 1.3vw, 18px);
  line-height: 1.82;
  color: var(--paper);
  max-width: 62ch;
}

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

.page-about .chapter__prose h3 {
  margin: 0 0 6px;
  font-size: 17px;
  font-weight: 800;
  letter-spacing: -.01em;
  color: var(--paper);
}

/* ---------- 引言 ---------- */

.page-about .about-quote {
  margin: 28px 0;
  padding: 22px 24px;
  background: var(--ink-2);
  border-left: 3px solid var(--orange);
  max-width: 60ch;
}

.page-about .about-quote p {
  margin: 0 0 12px;
  font-size: clamp(18px, 2vw, 24px);
  font-weight: 700;
  line-height: 1.5;
  letter-spacing: -.01em;
  color: var(--white);
}

.page-about .about-quote cite {
  font-family: var(--font-mono);
  font-style: normal;
  font-size: 12px;
  letter-spacing: .08em;
  color: var(--mist);
}

/* ---------- 四步流程 ---------- */

.page-about .steps {
  list-style: none;
  margin: 26px 0 0;
  padding: 0;
  counter-reset: none;
}

.page-about .steps__item {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 16px;
  padding: 20px 0 20px 0;
  border-top: 1px solid rgba(23, 56, 79, .8);
}

.page-about .steps__item:first-child {
  border-top: none;
  padding-top: 4px;
}

.page-about .steps__num {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .08em;
  color: var(--jade);
  padding-top: .3em;
}

.page-about .steps__item p {
  margin: 0;
  font-size: 16px;
  line-height: 1.78;
  color: var(--mist);
  max-width: 58ch;
}

/* ---------- 清单 ---------- */

.page-about .about-list {
  list-style: none;
  margin: 26px 0 0;
  padding: 0;
  border-top: 1px solid var(--line);
}

.page-about .about-list li {
  display: grid;
  grid-template-columns: minmax(72px, 96px) minmax(0, 1fr);
  gap: 14px;
  padding: 14px 0;
  border-bottom: 1px solid rgba(23, 56, 79, .8);
  align-items: baseline;
}

.page-about .about-list__k {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .06em;
  color: var(--orange-soft);
}

.page-about .about-list__v {
  font-size: 15px;
  line-height: 1.7;
  color: var(--mist);
}

/* ---------- 图片 ---------- */

.page-about .about-media {
  margin: 0;
  min-width: 0;
}

.page-about .about-media .media__frame {
  border: 1px solid var(--line);
  background: var(--ink-3);
  overflow: hidden;
}

.page-about .about-media img {
  display: block;
  width: 100%;
  height: auto;
  max-width: 100%;
  object-fit: cover;
}

.page-about .about-media .media__caption {
  margin-top: 10px;
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.6;
  letter-spacing: .04em;
  color: var(--mist);
}

/* ---------- 时间线 ---------- */

.page-about .timeline {
  list-style: none;
  margin: 26px 0 0;
  padding: 0 0 0 20px;
  position: relative;
}

.page-about .timeline::before {
  content: "";
  position: absolute;
  left: 3px;
  top: 8px;
  bottom: 8px;
  width: 1px;
  background: var(--line);
}

.page-about .timeline__item {
  position: relative;
  padding: 0 0 26px 22px;
}

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

.page-about .timeline__item::before {
  content: "";
  position: absolute;
  left: -20px;
  top: 8px;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--ink);
  border: 1px solid var(--jade);
}

.page-about .timeline__item--start::before,
.page-about .timeline__item--now::before {
  background: var(--orange);
  border-color: var(--orange);
  box-shadow: 0 0 0 4px rgba(255, 107, 53, .16);
}

.page-about .timeline__year {
  display: block;
  font-family: var(--font-mono);
  font-size: 15px;
  font-weight: 700;
  letter-spacing: .08em;
  color: var(--orange-soft);
  margin-bottom: 6px;
}

.page-about .timeline__item--now .timeline__year {
  color: var(--orange);
}

.page-about .timeline__text h3 {
  margin: 0 0 6px;
  font-size: 17px;
  font-weight: 800;
  color: var(--paper);
  letter-spacing: -.01em;
}

.page-about .timeline__text p {
  margin: 0;
  font-size: 15px;
  line-height: 1.78;
  color: var(--mist);
  max-width: 54ch;
}

/* ---------- 数据 ---------- */

.page-about .stats {
  display: grid;
  gap: 1px;
  margin: 26px 0 0;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .stats__cell {
  background: var(--ink-3);
  padding: 22px 20px 24px;
}

.page-about .stats__cell dt {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--mist);
  margin-bottom: 12px;
}

.page-about .stats__cell dd {
  margin: 0 0 10px;
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px;
}

.page-about .stats__num {
  font-size: clamp(34px, 5vw, 52px);
  font-weight: 900;
  line-height: 1;
  letter-spacing: -.03em;
  color: var(--paper);
}

.page-about .stats__unit {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .06em;
  color: var(--jade);
}

.page-about .stats__desc {
  margin: 0;
  font-size: 14px;
  line-height: 1.7;
  color: var(--mist);
}

.page-about .stats__cell--wide {
  background: var(--ink-2);
}

/* ---------- 下一步 ---------- */

.page-about .about-next {
  margin-top: clamp(48px, 7vw, 96px);
  padding: clamp(32px, 5vw, 64px) 0 clamp(8px, 2vw, 24px);
  border-top: 1px solid var(--line);
  background: var(--ink-deep);
}

.page-about .about-next h2 {
  margin: 0 0 28px;
  font-size: clamp(24px, 3.2vw, 40px);
  font-weight: 900;
  line-height: 1.15;
  letter-spacing: -.03em;
  color: var(--paper);
}

.page-about .about-next__grid {
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .about-next__item {
  display: block;
  padding: 22px 20px 24px;
  background: var(--ink-3);
  text-decoration: none;
  transition: background var(--dur) var(--ease), transform var(--dur) var(--ease);
}

.page-about .about-next__item:hover {
  background: var(--ink-2);
  transform: translateY(-2px);
}

.page-about .about-next__num {
  display: block;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--orange);
  margin-bottom: 12px;
}

.page-about .about-next__item h3 {
  margin: 0 0 8px;
  font-size: 18px;
  font-weight: 800;
  color: var(--paper);
  letter-spacing: -.01em;
}

.page-about .about-next__item p {
  margin: 0 0 16px;
  font-size: 14px;
  line-height: 1.7;
  color: var(--mist);
}

.page-about .about-next__go {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .08em;
  color: var(--jade);
  border-bottom: 1px solid rgba(134, 205, 184, .45);
  padding-bottom: 2px;
}

.page-about .about-next__item:hover .about-next__go {
  color: var(--orange-soft);
  border-bottom-color: rgba(255, 179, 138, .6);
}

/* ---------- 平板 ---------- */

@media (min-width: 720px) {
  .page-about .steps__item {
    grid-template-columns: 56px minmax(0, 1fr);
    gap: 20px;
  }

  .page-about .about-list li {
    grid-template-columns: 120px minmax(0, 1fr);
    gap: 24px;
  }

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

  .page-about .stats__cell--wide {
    grid-column: 1 / -1;
  }

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

  .page-about .timeline {
    padding-left: 0;
    display: grid;
    grid-template-columns: 120px minmax(0, 1fr);
    column-gap: 24px;
    row-gap: 0;
  }

  .page-about .timeline::before {
    left: 118px;
    top: 10px;
  }

  .page-about .timeline__item {
    display: contents;
  }

  .page-about .timeline__item::before {
    display: none;
  }

  .page-about .timeline__year {
    grid-column: 1;
    text-align: right;
    padding: 0;
    margin: 0 0 24px;
    align-self: start;
    position: relative;
  }

  .page-about .timeline__year::after {
    content: "";
    position: absolute;
    right: -14px;
    top: 6px;
    width: 9px;
    height: 9px;
    border-radius: 50%;
    background: var(--ink);
    border: 1px solid var(--jade);
  }

  .page-about .timeline__item--start .timeline__year::after,
  .page-about .timeline__item--now .timeline__year::after {
    background: var(--orange);
    border-color: var(--orange);
    box-shadow: 0 0 0 4px rgba(255, 107, 53, .16);
  }

  .page-about .timeline__text {
    grid-column: 2;
    padding: 0 0 28px 24px;
    border-left: 1px solid transparent;
  }
}

/* ---------- 桌面 ---------- */

@media (min-width: 1000px) {
  .page-about .about-intro__grid {
    grid-template-columns: var(--about-rail) minmax(0, 1fr);
    column-gap: clamp(32px, 5vw, 72px);
  }

  .page-about .about-intro__main {
    padding-right: clamp(0px, 4vw, 64px);
  }

  .page-about .chapter__head {
    display: grid;
    grid-template-columns: 56px minmax(0, 1fr) 32px;
    align-items: center;
    gap: 24px;
  }

  .page-about .chapter__num {
    font-size: clamp(22px, 2.4vw, 34px);
    font-weight: 700;
    padding-top: 0;
  }

  .page-about .chapter__mark {
    margin-top: 0;
  }

  .page-about .chapter__body {
    display: grid;
    grid-template-columns: minmax(0, 1.15fr) minmax(0, .85fr);
    column-gap: clamp(32px, 5vw, 72px);
    padding-left: 80px;
    align-items: start;
  }

  .page-about .chapter__body--reverse {
    grid-template-columns: minmax(0, .85fr) minmax(0, 1.15fr);
  }

  .page-about .chapter__body--reverse .chapter__prose {
    order: 2;
  }

  .page-about .chapter__body--reverse .about-media {
    order: 1;
  }

  .page-about .chapter__body > .chapter__prose:only-child,
  .page-about .chapter__body > .timeline,
  .page-about .chapter__body > .stats {
    grid-column: 1 / -1;
    max-width: 78ch;
  }

  .page-about .chapter__body--reverse {
    align-items: center;
  }

  .page-about .about-media--offset {
    transform: translateY(24px);
  }

  .page-about .stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
    max-width: none;
  }

  .page-about .stats__cell--wide {
    grid-column: span 4;
  }

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

@media (prefers-reduced-motion: reduce) {
  .page-about .about-next__item,
  .page-about .chapter__mark::before,
  .page-about .chapter__mark::after,
  .page-about .chapter__title {
    transition: none;
  }

  .page-about .about-next__item:hover {
    transform: none;
  }
}
<<<END>>>