.page-about {
  --ab-read: 38rem;
  --ab-cut: 16px;
  --ab-cover-cut: 22px;
  background: var(--mist);
  color: var(--ink);
}

/* ---------- 封面 ---------- */

.page-about .ab-cover {
  position: relative;
  overflow: hidden;
  background: var(--violet-deep);
  color: var(--mist);
  padding: clamp(48px, 8vw, 96px) 0 clamp(44px, 6vw, 76px);
  isolation: isolate;
}

.page-about .ab-cover__bg {
  position: absolute;
  inset: -6% -5%;
  z-index: 0;
  background:
    radial-gradient(115% 88% at 84% 6%, rgba(18, 92, 140, .82) 0%, rgba(42, 30, 82, 0) 58%),
    radial-gradient(80% 76% at 6% 94%, rgba(224, 166, 60, .18) 0%, rgba(21, 15, 46, 0) 62%),
    linear-gradient(155deg, var(--violet-deep) 0%, var(--violet) 46%, var(--lake-deep) 100%);
  animation: ab-drift 12s ease-in-out infinite alternate;
  will-change: transform;
}

@keyframes ab-drift {
  from { transform: translate3d(0, 0, 0) scale(1.02); }
  to   { transform: translate3d(-1.4%, 1.1%, 0) scale(1.05); }
}

.page-about .ab-cover__grid {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(245, 248, 251, .07) 1px, transparent 1px),
    linear-gradient(90deg, rgba(245, 248, 251, .07) 1px, transparent 1px);
  background-size: 64px 64px;
  -webkit-mask-image: linear-gradient(180deg, rgba(0, 0, 0, .9), rgba(0, 0, 0, .12));
  mask-image: linear-gradient(180deg, rgba(0, 0, 0, .9), rgba(0, 0, 0, .12));
}

.page-about .ab-cover__grid::after {
  content: "";
  position: absolute;
  left: -8%;
  right: -8%;
  top: 64%;
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(224, 166, 60, .6), transparent);
  transform: rotate(-6.5deg);
}

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

.page-about .ab-cover__kicker {
  color: var(--gold-light);
}

.page-about .ab-cover h1 {
  margin: 18px 0 0;
  font-size: clamp(30px, 6vw, 62px);
  font-weight: 900;
  letter-spacing: .06em;
  line-height: 1.18;
  color: var(--mist);
  max-width: 20em;
}

.page-about .ab-cover__lede {
  margin: clamp(18px, 3vw, 28px) 0 0;
  max-width: 40rem;
  font-size: clamp(15px, 1.7vw, 17px);
  line-height: 1.92;
  color: var(--mist-90);
}

.page-about .ab-facts {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: clamp(14px, 2.4vw, 26px);
  margin: clamp(32px, 5vw, 56px) 0 0;
  padding: clamp(20px, 3vw, 30px) 0 0;
  border-top: 1px solid var(--line-inv);
}

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

.page-about .ab-fact dt {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .14em;
  color: var(--mist-50);
  margin-bottom: 10px;
}

.page-about .ab-fact__v {
  margin: 0;
  display: flex;
  align-items: baseline;
  gap: 8px;
  flex-wrap: wrap;
}

.page-about .ab-fact__n {
  font-family: var(--font-mono);
  font-size: clamp(46px, 8vw, 88px);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -.01em;
  color: var(--gold);
  font-variant-numeric: tabular-nums;
}

.page-about .ab-fact__u {
  font-size: 13px;
  letter-spacing: .06em;
  color: var(--mist-70);
}

/* ---------- 主体布局 ---------- */

.page-about .ab-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(28px, 5vw, 48px);
  padding-top: clamp(40px, 6vw, 72px);
  padding-bottom: clamp(64px, 9vw, 120px);
  align-items: start;
}

@media (min-width: 960px) {
  .page-about .ab-layout {
    grid-template-columns: 186px minmax(0, 1fr);
    gap: clamp(40px, 7vw, 104px);
  }
}

/* ---------- 左侧索引 ---------- */

.page-about .ab-index {
  position: static;
  background: none;
  border: 0;
  padding: 0;
}

@media (min-width: 960px) {
  .page-about .ab-index {
    position: sticky;
    top: 128px;
  }
}

.page-about .ab-index__title {
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 400;
  letter-spacing: .2em;
  text-transform: uppercase;
  color: var(--slate);
}

.page-about .ab-index .eb-index__list {
  list-style: none;
  margin: 0;
  padding: 0;
}

@media (max-width: 959px) {
  .page-about .ab-index .eb-index__list {
    display: flex;
    gap: 6px;
    overflow-x: auto;
    padding-bottom: 6px;
    scrollbar-width: none;
  }
  .page-about .ab-index .eb-index__list::-webkit-scrollbar { display: none; }
  .page-about .ab-index .eb-index__list li { flex: 0 0 auto; }
}

@media (min-width: 960px) {
  .page-about .ab-index .eb-index__list {
    position: relative;
    display: flex;
    flex-direction: column;
    gap: 2px;
  }
  .page-about .ab-index .eb-index__list::before {
    content: "";
    position: absolute;
    left: 15px;
    top: 24px;
    bottom: 24px;
    width: 1px;
    background: var(--line-strong);
  }
}

.page-about .ab-index .eb-index__link {
  display: grid;
  grid-template-columns: 30px minmax(0, 1fr);
  align-items: center;
  gap: 12px;
  padding: 7px 0;
  font-size: 13px;
  letter-spacing: .04em;
  color: var(--slate);
  text-decoration: none;
  border-radius: 2px;
  transition: color .2s ease;
}

.page-about .ab-index .eb-index__no {
  position: relative;
  z-index: 1;
  width: 30px;
  height: 30px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  background: var(--mist);
  border: 1px solid var(--line-strong);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .06em;
  color: var(--slate);
  transition: background .2s ease, border-color .2s ease, color .2s ease;
}

.page-about .ab-index .eb-index__link:hover {
  color: var(--lake);
}

.page-about .ab-index .eb-index__link:hover .eb-index__no {
  border-color: var(--lake-light);
  color: var(--lake);
}

.page-about .ab-index .eb-index__link.is-active {
  color: var(--ink);
  font-weight: 700;
}

.page-about .ab-index .eb-index__link.is-active .eb-index__no {
  background: var(--gold);
  border-color: var(--gold);
  color: var(--ink);
}

@media (max-width: 959px) {
  .page-about .ab-index .eb-index__link {
    grid-template-columns: 24px auto;
    gap: 8px;
    padding: 5px 12px 5px 5px;
    border: 1px solid var(--line);
    white-space: nowrap;
  }
  .page-about .ab-index .eb-index__no {
    width: 24px;
    height: 24px;
    font-size: 10px;
  }
}

/* ---------- 章节 ---------- */

.page-about .ab-stream {
  min-width: 0;
}

.page-about .ab-chapter {
  position: relative;
  padding-bottom: clamp(44px, 7vw, 84px);
}

.page-about .ab-chapter + .ab-chapter {
  padding-top: clamp(40px, 6vw, 76px);
}

.page-about .ab-chapter__no {
  display: block;
  font-family: var(--font-mono);
  font-size: 14px;
  font-weight: 700;
  letter-spacing: .2em;
  color: var(--lake);
  margin-bottom: 10px;
}

.page-about .ab-chapter h2 {
  margin: 0 0 14px;
  font-size: clamp(23px, 3.2vw, 33px);
  font-weight: 900;
  letter-spacing: .055em;
  line-height: 1.34;
  color: var(--ink);
  max-width: 22em;
}

.page-about .ab-chapter__rule {
  display: block;
  width: 48px;
  height: 3px;
  background: var(--gold);
  margin-bottom: clamp(20px, 3vw, 32px);
}

.page-about .ab-chapter p {
  margin: 0 0 1.25em;
  font-size: 16px;
  line-height: 1.92;
  color: var(--ink);
}

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

.page-about .eb-prose--narrow {
  max-width: var(--ab-read);
}

.page-about .ab-inline-link {
  color: var(--lake);
  text-decoration: underline;
  text-decoration-color: rgba(18, 92, 140, .34);
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
  transition: color .18s ease, text-decoration-color .18s ease;
}

.page-about .ab-inline-link:hover {
  color: var(--lake-deep);
  text-decoration-color: var(--gold);
}

/* ---------- 图 ---------- */

.page-about .ab-figure {
  margin: clamp(24px, 4vw, 40px) 0;
}

.page-about .ab-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  background: var(--lake-deep);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - var(--ab-cut)), calc(100% - var(--ab-cut)) 100%, 0 100%);
}

.page-about .ab-figure figcaption {
  margin-top: 12px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .04em;
  line-height: 1.7;
  color: var(--slate);
}

.page-about .ab-figure--wide {
  max-width: 44rem;
}

.page-about .ab-figure--inset-left {
  max-width: 100%;
}

.page-about .ab-figure--inset-right {
  max-width: 100%;
}

@media (min-width: 760px) {
  .page-about .ab-figure--inset-left {
    max-width: 360px;
    margin-left: 0;
    margin-right: auto;
  }
  .page-about .ab-figure--inset-right {
    max-width: 320px;
    margin-left: auto;
    margin-right: 0;
  }
}

/* ---------- 三个步骤 ---------- */

.page-about .ab-steps {
  list-style: none;
  margin: clamp(26px, 4vw, 40px) 0 0;
  padding: 0;
  max-width: var(--ab-read);
}

.page-about .ab-step {
  padding: clamp(18px, 3vw, 26px) 0;
  border-top: 1px solid var(--line);
}

.page-about .ab-step:last-child {
  border-bottom: 1px solid var(--line);
}

.page-about .ab-step__no {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .18em;
  color: var(--lake);
  padding: 2px 8px;
  border: 1px solid var(--lake-light);
  border-radius: 2px;
  margin-bottom: 10px;
}

.page-about .ab-step__title {
  margin: 0 0 8px;
  font-size: 19px;
  font-weight: 800;
  letter-spacing: .05em;
  color: var(--ink);
}

.page-about .ab-step__text {
  margin: 0;
  font-size: 15.5px;
  line-height: 1.9;
  color: var(--ink);
}

/* ---------- 季度色带 ---------- */

.page-about .ab-quarters {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 6px;
  margin: clamp(26px, 4vw, 42px) 0 0;
}

@media (min-width: 720px) {
  .page-about .ab-quarters {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

.page-about .ab-quarter {
  position: relative;
  padding: 20px 14px 18px;
  border-top: 3px solid var(--lake);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 14px), calc(100% - 14px) 100%, 0 100%);
}

.page-about .ab-quarter:nth-child(1) {
  background: linear-gradient(180deg, rgba(127, 182, 214, .26), rgba(127, 182, 214, .05));
  border-top-color: var(--lake-light);
}
.page-about .ab-quarter:nth-child(2) {
  background: linear-gradient(180deg, rgba(18, 92, 140, .2), rgba(18, 92, 140, .04));
  border-top-color: var(--lake);
}
.page-about .ab-quarter:nth-child(3) {
  background: linear-gradient(180deg, rgba(10, 58, 92, .17), rgba(10, 58, 92, .04));
  border-top-color: var(--lake-deep);
}
.page-about .ab-quarter:nth-child(4) {
  background: linear-gradient(180deg, rgba(42, 30, 82, .17), rgba(42, 30, 82, .04));
  border-top-color: var(--violet);
}

.page-about .ab-quarter__n {
  display: block;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .18em;
  color: var(--slate);
  margin-bottom: 10px;
}

.page-about .ab-quarter__t {
  display: block;
  font-size: 15px;
  font-weight: 700;
  letter-spacing: .03em;
  line-height: 1.5;
  color: var(--ink);
}

.page-about .ab-quarter__s {
  display: block;
  margin-top: 6px;
  font-size: 12.5px;
  line-height: 1.65;
  color: var(--slate);
}

.page-about .ab-quarters__note {
  margin: 14px 0 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .04em;
  color: var(--slate);
  max-width: var(--ab-read);
}

/* ---------- 收尾 ---------- */

.page-about .ab-outcome {
  position: relative;
  margin-top: clamp(36px, 6vw, 72px);
  padding-top: clamp(30px, 5vw, 52px);
  border-top: 1px solid var(--line);
}

.page-about .ab-outcome::before {
  content: "";
  position: absolute;
  top: -2px;
  left: 0;
  width: 64px;
  height: 3px;
  background: var(--gold);
}

.page-about .ab-outcome h2 {
  margin: 10px 0 clamp(22px, 3.4vw, 34px);
  font-size: clamp(23px, 3.2vw, 33px);
  font-weight: 900;
  letter-spacing: .055em;
  line-height: 1.34;
  color: var(--ink);
}

.page-about .ab-fold {
  max-width: var(--ab-read);
}

.page-about .ab-fold .eb-fold__item {
  border-top: 1px solid var(--line);
}

.page-about .ab-fold .eb-fold__item:last-child {
  border-bottom: 1px solid var(--line);
}

.page-about .ab-fold .eb-fold__sum {
  cursor: pointer;
  padding: 18px 0;
  font-size: 16.5px;
  font-weight: 700;
  letter-spacing: .03em;
  line-height: 1.6;
  color: var(--ink);
  list-style: none;
}

.page-about .ab-fold .eb-fold__sum::-webkit-details-marker {
  display: none;
}

.page-about .ab-fold .eb-fold__sum::marker,
.page-about .ab-fold .eb-fold__sum::before {
  content: none;
}

.page-about .ab-fold .eb-fold__item[open] .eb-fold__sum {
  color: var(--lake-deep);
}

.page-about .ab-fold .eb-fold__body {
  padding: 0 0 20px;
}

.page-about .ab-fold .eb-fold__body p {
  margin: 0;
  max-width: var(--ab-read);
  font-size: 15.5px;
  line-height: 1.92;
  color: var(--slate);
}

/* ---------- 动效降级 ---------- */

@media (prefers-reduced-motion: reduce) {
  .page-about .ab-cover__bg {
    animation: none;
  }
  .page-about .ab-index .eb-index__link,
  .page-about .ab-index .eb-index__no,
  .page-about .ab-inline-link {
    transition: none;
  }
}
<<<END>>>