.page-about {
  --ab-rule: rgba(27, 79, 134, 0.22);
  --ab-rule-ink: rgba(18, 23, 31, 0.14);
  --ab-year: clamp(26px, 4.2vw, 40px);
  background: var(--paper);
  color: var(--ink);
}

/* ==================== 首屏 ==================== */
.page-about .ab-hero {
  position: relative;
  overflow: hidden;
  padding: clamp(22px, 4vw, 40px) 0 clamp(46px, 7vw, 92px);
}

.page-about .ab-hero::before {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: min(56%, 680px);
  height: 80%;
  background: linear-gradient(156deg, var(--ice) 0%, rgba(207, 224, 239, 0.16) 84%);
  clip-path: polygon(38% 0, 100% 0, 100% 100%, 0 100%);
  pointer-events: none;
  z-index: 0;
}

.page-about .ab-hero::after {
  content: "";
  position: absolute;
  right: 0;
  bottom: 0;
  width: min(56%, 680px);
  height: 5px;
  background: var(--orange);
  z-index: 0;
}

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

.page-about .ab-hero .breadcrumb {
  margin: 0 0 clamp(26px, 5vw, 54px);
}

.page-about .ab-hero__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(18px, 3vw, 40px);
}

.page-about .ab-hero__lead .page-title {
  margin: 10px 0 0;
  color: var(--blue);
  line-height: 1.02;
}

.page-about .ab-hero__copy .page-lede {
  margin: 0;
  max-width: 46ch;
}

.page-about .ab-facts {
  list-style: none;
  margin: clamp(22px, 4vw, 34px) 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  border-top: 1px solid var(--ab-rule);
  border-left: 1px solid var(--ab-rule);
}

.page-about .ab-facts li {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 14px 16px;
  border-right: 1px solid var(--ab-rule);
  border-bottom: 1px solid var(--ab-rule);
}

.page-about .ab-facts__num {
  font-family: var(--font-mono);
  font-size: var(--fs-28);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.03em;
  color: var(--blue);
}

.page-about .ab-facts__txt {
  font-size: var(--fs-14);
  line-height: 1.5;
  color: rgba(18, 23, 31, 0.76);
}

/* ==================== 章节骨架 ==================== */
.page-about .ab-section {
  position: relative;
  padding: clamp(50px, 8vw, 104px) 0;
}

.page-about .ab-section + .ab-section {
  border-top: 1px solid var(--ab-rule-ink);
}

.page-about .ab-section--seam {
  background: var(--paper-2);
}

.page-about .ab-section--ice {
  background: var(--ice);
}

.page-about .ab-head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px 14px;
  margin-bottom: clamp(12px, 2vw, 20px);
}

.page-about .ab-num {
  font-family: var(--font-mono);
  font-size: clamp(28px, 4.6vw, 44px);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.05em;
  color: var(--blue);
}

.page-about .ab-label {
  font-family: var(--font-mono);
  font-size: var(--fs-14);
  font-weight: 700;
  letter-spacing: 0.18em;
  color: var(--green);
}

.page-about .ab-h2 {
  margin: 0 0 clamp(18px, 3vw, 32px);
  font-size: var(--fs-40);
  font-weight: 900;
  line-height: 1.16;
  letter-spacing: -0.02em;
  color: var(--ink);
}

.page-about .ab-lede {
  margin: 0 0 clamp(26px, 4vw, 44px);
  max-width: 62ch;
  font-size: var(--fs-20);
  line-height: 1.7;
  color: rgba(18, 23, 31, 0.86);
}

/* ==================== 非对称分栏 ==================== */
.page-about .ab-split {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(24px, 4vw, 48px);
}

.page-about .ab-aside {
  border-left: 3px solid var(--orange);
  padding-left: clamp(14px, 2vw, 22px);
}

.page-about .ab-yearmark {
  margin: 0;
  font-family: var(--font-mono);
  font-size: clamp(54px, 10vw, 92px);
  font-weight: 700;
  line-height: 0.9;
  letter-spacing: -0.06em;
  color: var(--blue);
}

.page-about .ab-yearmark__txt {
  margin: 12px 0 0;
  font-family: var(--font-mono);
  font-size: var(--fs-14);
  letter-spacing: 0.14em;
  color: var(--green);
}

.page-about .ab-prose {
  max-width: 68ch;
}

.page-about .ab-prose p {
  margin: 0 0 1.1em;
  font-size: var(--fs-17);
  line-height: 1.78;
}

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

/* ==================== 图片与图注 ==================== */
.page-about .ab-banner {
  margin: 0 0 clamp(32px, 5vw, 56px);
}

.page-about .ab-banner img,
.page-about .ab-media img,
.page-about .ab-compare__media img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  border: 1px solid var(--ab-rule);
}

.page-about .ab-media {
  margin: 0;
}

.page-about .ab-media img {
  aspect-ratio: 4 / 3;
}

/* ==================== 时间轴 ==================== */
.page-about .ab-timeline {
  position: relative;
  list-style: none;
  margin: 0 0 clamp(36px, 5vw, 64px);
  padding: 0;
}

.page-about .ab-timeline::before {
  content: "";
  position: absolute;
  left: 5px;
  top: 34px;
  bottom: 34px;
  width: 1px;
  background: var(--ab-rule);
}

.page-about .ab-node {
  position: relative;
  padding-left: 34px;
}

.page-about .ab-node + .ab-node {
  margin-top: clamp(10px, 1.6vw, 18px);
}

.page-about .ab-node::before {
  content: "";
  position: absolute;
  left: 0;
  top: 31px;
  width: 11px;
  height: 11px;
  background: var(--blue);
  transition: background 160ms var(--ease);
}

.page-about .ab-node__box {
  position: relative;
  display: block;
}

.page-about .ab-node__sum {
  position: relative;
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px 16px;
  list-style: none;
  cursor: pointer;
  padding: 18px 38px 0 0;
}

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

.page-about .ab-node__sum::marker {
  content: "";
}

.page-about .ab-node__sum::after {
  content: "+";
  position: absolute;
  right: 0;
  top: 18px;
  width: 24px;
  height: 24px;
  display: grid;
  place-items: center;
  border: 1px solid var(--ab-rule);
  font-family: var(--font-mono);
  font-size: 15px;
  line-height: 1;
  color: var(--blue);
  transition: background 160ms var(--ease), border-color 160ms var(--ease), color 160ms var(--ease);
}

.page-about .ab-node__box[open] .ab-node__sum::after {
  content: "−";
  color: var(--paper);
  background: var(--orange);
  border-color: var(--orange);
}

.page-about .ab-year {
  font-family: var(--font-mono);
  font-size: var(--ab-year);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.04em;
  color: var(--blue);
  transition: color 160ms var(--ease);
}

.page-about .ab-node__title {
  font-size: var(--fs-20);
  font-weight: 700;
  line-height: 1.35;
  color: var(--ink);
}

.page-about .ab-node__sum:hover .ab-year,
.page-about .ab-node__box[open] .ab-year {
  color: var(--orange);
}

.page-about .ab-node__body {
  max-width: 62ch;
  padding: 12px 0 8px;
  border-top: 1px solid var(--ab-rule-ink);
  margin-top: 16px;
}

.page-about .ab-node__body p {
  margin: 0;
  font-size: var(--fs-17);
  line-height: 1.78;
  color: rgba(18, 23, 31, 0.88);
}

/* ==================== 前后对照 ==================== */
.page-about .ab-compare {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(20px, 3vw, 36px);
}

.page-about .ab-compare__media {
  margin: 0;
}

.page-about .ab-compare__panel {
  display: grid;
  grid-template-columns: 1fr;
  border: 1px solid var(--ab-rule);
}

.page-about .ab-cmp-col {
  padding: clamp(18px, 2.6vw, 30px);
}

.page-about .ab-cmp-col--old {
  background: var(--paper-2);
}

.page-about .ab-cmp-col--new {
  background: var(--paper);
}

.page-about .ab-cmp-num {
  margin: 12px 0 6px;
  font-family: var(--font-mono);
  font-size: clamp(40px, 6vw, 64px);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.05em;
}

.page-about .ab-cmp-col--old .ab-cmp-num {
  color: rgba(18, 23, 31, 0.5);
  text-decoration: line-through;
  text-decoration-thickness: 2px;
}

.page-about .ab-cmp-col--new .ab-cmp-num {
  color: var(--orange);
}

.page-about .ab-cmp-cap {
  margin: 0 0 16px;
  font-size: var(--fs-14);
  line-height: 1.55;
  color: rgba(18, 23, 31, 0.78);
}

.page-about .ab-cmp-col ul {
  list-style: none;
  margin: 0;
  padding: 0;
  border-top: 1px solid var(--ab-rule);
}

.page-about .ab-cmp-col li {
  padding: 10px 0;
  border-bottom: 1px solid var(--ab-rule);
  font-size: var(--fs-14);
  line-height: 1.6;
  color: rgba(18, 23, 31, 0.82);
}

/* ==================== 地域示意 ==================== */
.page-about .ab-geo {
  margin: 0;
}

.page-about .ab-geo svg {
  display: block;
  width: 100%;
  height: auto;
}

.page-about .ab-geo .ab-geo__val {
  font-family: var(--font-mono);
  font-size: 22px;
  font-weight: 700;
  fill: var(--ink);
}

.page-about .ab-geo .ab-geo-lbl {
  font-family: var(--font-body);
  font-size: 15px;
  fill: rgba(18, 23, 31, 0.8);
}

.page-about .ab-geo figcaption {
  margin-top: 14px;
}

/* ==================== 路线图色带 ==================== */
.page-about .ab-band {
  background: var(--orange-soft);
  border-left: 6px solid var(--orange);
  padding: clamp(26px, 4vw, 54px);
}

.page-about .ab-band .ab-h2 {
  margin-bottom: clamp(16px, 2.6vw, 28px);
}

.page-about .ab-band__cols {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(16px, 2.6vw, 34px);
}

.page-about .ab-band__cols p {
  margin: 0;
  font-size: var(--fs-17);
  line-height: 1.78;
  color: rgba(18, 23, 31, 0.94);
}

/* ==================== 下一步 ==================== */
.page-about .ab-next {
  list-style: none;
  margin: 0 0 clamp(24px, 3.4vw, 40px);
  padding: 0;
  display: grid;
  grid-template-columns: 1fr;
  border-top: 1px solid var(--ab-rule);
}

.page-about .ab-next li {
  border-bottom: 1px solid var(--ab-rule);
}

.page-about .ab-next a {
  display: grid;
  gap: 6px;
  padding: clamp(16px, 2.4vw, 24px) 0;
  text-decoration: none;
  color: var(--ink);
  transition: color 160ms var(--ease);
}

.page-about .ab-next a:hover,
.page-about .ab-next a:focus-visible {
  color: var(--orange);
}

.page-about .ab-next__t {
  font-size: var(--fs-20);
  font-weight: 700;
  letter-spacing: -0.01em;
}

.page-about .ab-next__d {
  font-size: var(--fs-14);
  line-height: 1.65;
  color: rgba(18, 23, 31, 0.74);
}

.page-about .ab-next a:hover .ab-next__d {
  color: rgba(18, 23, 31, 0.9);
}

/* ==================== 响应式 ==================== */
@media (min-width: 640px) {
  .page-about .ab-facts {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .ab-compare__panel {
    grid-template-columns: 1fr 1fr;
  }
}

@media (min-width: 760px) {
  .page-about .ab-band__cols {
    grid-template-columns: 1fr 1fr;
  }

  .page-about .ab-next {
    grid-template-columns: 1fr 1fr;
  }

  .page-about .ab-next li:nth-child(odd) {
    padding-right: clamp(20px, 3vw, 42px);
    border-right: 1px solid var(--ab-rule);
  }

  .page-about .ab-next li:nth-child(even) {
    padding-left: clamp(20px, 3vw, 42px);
  }
}

@media (min-width: 820px) {
  .page-about .ab-split--aside {
    grid-template-columns: minmax(0, 0.32fr) minmax(0, 0.68fr);
    gap: clamp(32px, 5vw, 76px);
  }

  .page-about .ab-split--media {
    grid-template-columns: minmax(0, 0.58fr) minmax(0, 0.42fr);
    gap: clamp(32px, 4vw, 56px);
    align-items: start;
  }

  .page-about .ab-split--geo {
    grid-template-columns: minmax(0, 0.52fr) minmax(0, 0.48fr);
    gap: clamp(32px, 4vw, 60px);
    align-items: center;
  }

  .page-about .ab-node {
    padding-left: 42px;
  }

  .page-about .ab-timeline::before {
    left: 5px;
  }
}

@media (min-width: 900px) {
  .page-about .ab-hero__grid {
    grid-template-columns: minmax(0, 0.88fr) minmax(0, 1.12fr);
    align-items: end;
    gap: clamp(32px, 5vw, 76px);
  }

  .page-about .ab-compare {
    grid-template-columns: minmax(0, 0.42fr) minmax(0, 0.58fr);
    align-items: stretch;
  }

  .page-about .ab-compare__media img {
    height: 100%;
    aspect-ratio: 8 / 5;
  }
}

@media (max-width: 859px) {
  .page-about .ab-hero::before {
    width: 100%;
    height: 46%;
    clip-path: polygon(0 0, 100% 0, 100% 38%, 0 100%);
    opacity: 0.7;
  }

  .page-about .ab-hero::after {
    width: 34%;
    height: 4px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .ab-node,
  .page-about .ab-node::before,
  .page-about .ab-year,
  .page-about .ab-node__sum::after,
  .page-about .ab-next a {
    transition: none;
  }
}
<<<END>>>