.page-about {
  display: block;
  color: var(--white);
  background: var(--ink);
  overflow-x: clip;
}

/* ---------- 面包屑 ---------- */
.page-about .breadcrumb {
  padding-top: calc(var(--unit) * 11);
  font-family: var(--font-mono);
  font-size: var(--fs-6);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--grey);
}

.page-about .breadcrumb a {
  color: var(--grey);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 0.2s var(--ease), border-color 0.2s var(--ease);
}

.page-about .breadcrumb a:hover,
.page-about .breadcrumb a:focus-visible {
  color: var(--cyan);
  border-bottom-color: var(--cyan);
}

.page-about .breadcrumb span[aria-hidden="true"] {
  margin: 0 0.6em;
  color: var(--line);
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  isolation: isolate;
  overflow: hidden;
  padding: calc(var(--unit) * 7) 0 calc(var(--unit) * 12);
}

.page-about .about-hero::before {
  content: "";
  position: absolute;
  z-index: 0;
  top: -22%;
  right: -8%;
  width: 60%;
  height: 152%;
  background: var(--grad);
  opacity: 0.12;
  transform: rotate(-6deg);
  pointer-events: none;
}

.page-about .about-hero__inner {
  position: relative;
  z-index: 1;
  display: grid;
  gap: calc(var(--unit) * 7);
}

.page-about .about-hero__title {
  margin: calc(var(--unit) * 3) 0 0;
  font-family: var(--font-cn);
  font-weight: 900;
  font-size: var(--fs-1);
  line-height: 1.08;
  letter-spacing: -0.02em;
  color: var(--white);
}

.page-about .about-hero__en {
  display: block;
  margin-top: calc(var(--unit) * 2);
  font-family: var(--font-en);
  font-weight: 400;
  font-size: 0.3em;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--cyan);
}

.page-about .about-hero__lede {
  margin: calc(var(--unit) * 4) 0 0;
  max-width: 46ch;
  font-size: var(--fs-body);
  line-height: 1.85;
  color: var(--grey);
}

.page-about .about-index {
  border-top: 1px solid var(--line);
  padding-top: calc(var(--unit) * 3);
}

.page-about .about-index__title {
  margin: 0 0 calc(var(--unit) * 2.5);
  font-family: var(--font-mono);
  font-size: var(--fs-6);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--grey);
}

.page-about .about-index__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 2px;
}

.page-about .about-index__link {
  display: flex;
  align-items: baseline;
  gap: calc(var(--unit) * 2);
  padding: calc(var(--unit) * 1.1) 0;
  color: var(--grey);
  text-decoration: none;
  font-size: var(--fs-5);
  border-bottom: 1px solid var(--line);
  transition: color 0.2s var(--ease), padding-left 0.2s var(--ease);
}

.page-about .about-index__link:hover,
.page-about .about-index__link:focus-visible {
  color: var(--white);
  padding-left: calc(var(--unit) * 1);
}

.page-about .about-index__n {
  font-family: var(--font-mono);
  font-size: var(--fs-6);
  letter-spacing: 0.12em;
  color: var(--violet);
}

/* ---------- 通用章节头 ---------- */
.page-about .ab-head {
  display: grid;
  grid-template-columns: auto 1fr;
  column-gap: calc(var(--unit) * 2);
  align-items: baseline;
  padding-bottom: calc(var(--unit) * 2.5);
  margin-bottom: calc(var(--unit) * 6);
  border-bottom: 1px solid var(--line);
}

.page-about .ab-head__num {
  font-family: var(--font-mono);
  font-size: var(--fs-5);
  letter-spacing: 0.14em;
  color: var(--violet);
}

.page-about .ab-head__zh {
  margin: 0;
  font-family: var(--font-cn);
  font-weight: 900;
  font-size: var(--fs-2);
  line-height: 1.2;
  letter-spacing: -0.02em;
  color: var(--white);
}

.page-about .ab-head__en {
  grid-column: 2;
  margin: calc(var(--unit) * 0.8) 0 0;
  color: var(--cyan);
  opacity: 0.9;
}

/* ---------- 01 非对称主张区 ---------- */
.page-about .ab-split {
  display: grid;
  gap: calc(var(--unit) * 4);
}

.page-about .ab-split__num {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--fs-5);
  letter-spacing: 0.14em;
  color: var(--violet);
}

.page-about .ab-split__en {
  margin: calc(var(--unit) * 1.2) 0 0;
  color: var(--cyan);
  opacity: 0.85;
}

.page-about .ab-split__title {
  margin: 0 0 calc(var(--unit) * 4);
  font-family: var(--font-cn);
  font-weight: 900;
  font-size: var(--fs-3);
  line-height: 1.25;
  letter-spacing: -0.015em;
  color: var(--white);
}

.page-about .ab-prose {
  max-width: 62ch;
}

.page-about .ab-prose p {
  margin: 0 0 calc(var(--unit) * 2.5);
  font-size: var(--fs-body);
  line-height: 1.85;
  color: var(--grey);
}

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

.page-about .ab-pull {
  margin: calc(var(--unit) * 6) 0 0;
  max-width: 22ch;
  padding-left: calc(var(--unit) * 3);
  border-left: 2px solid var(--violet);
  font-family: var(--font-serif);
  font-size: var(--fs-3);
  line-height: 1.55;
  color: var(--white);
}

/* ---------- 02 中英双栏 ---------- */
.page-about .ab-dual {
  display: grid;
  gap: calc(var(--unit) * 5);
}

.page-about .ab-dual__col p {
  margin: 0 0 calc(var(--unit) * 2.5);
  font-size: var(--fs-body);
  line-height: 1.85;
  color: var(--grey);
}

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

.page-about .ab-dual__col--en p {
  font-size: var(--fs-5);
  line-height: 1.95;
  letter-spacing: 0.012em;
  color: rgba(174, 184, 204, 0.88);
}

/* ---------- 03 栏目体系 ---------- */
.page-about .ab-columns {
  display: grid;
  gap: calc(var(--unit) * 6);
}

.page-about .ab-columns__list {
  list-style: none;
  margin: 0;
  padding: 0;
  counter-reset: none;
}

.page-about .ab-col-item {
  display: grid;
  grid-template-columns: 40px 1fr;
  gap: calc(var(--unit) * 2.5);
  padding: calc(var(--unit) * 3.5) 0;
  border-top: 1px solid var(--line);
}

.page-about .ab-col-item__code {
  font-family: var(--font-mono);
  font-size: var(--fs-4);
  font-weight: 700;
  letter-spacing: 0.08em;
  line-height: 1.2;
  color: var(--violet);
}

.page-about .ab-col-item--b .ab-col-item__code {
  color: var(--cyan);
}

.page-about .ab-col-item--c .ab-col-item__code {
  color: var(--amber);
}

.page-about .ab-col-item--d .ab-col-item__code {
  color: var(--red);
}

.page-about .ab-col-item__name {
  margin: 0 0 calc(var(--unit) * 1);
  font-family: var(--font-cn);
  font-weight: 900;
  font-size: var(--fs-4);
  letter-spacing: -0.01em;
  color: var(--white);
}

.page-about .ab-col-item__desc {
  margin: 0;
  font-size: var(--fs-5);
  line-height: 1.85;
  color: var(--grey);
}

.page-about .ab-note {
  margin: calc(var(--unit) * 6) 0 0;
  padding-top: calc(var(--unit) * 3);
  border-top: 1px solid var(--line);
  max-width: 60ch;
  font-family: var(--font-serif);
  font-size: var(--fs-5);
  line-height: 1.8;
  color: var(--grey);
}

.page-about .ab-note--end {
  border-top-color: var(--line);
}

/* ---------- 图片框 ---------- */
.page-about .ab-figure {
  margin: 0;
}

.page-about .ab-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.page-about .ab-figure figcaption {
  margin-top: calc(var(--unit) * 1.5);
  font-family: var(--font-mono);
  font-size: var(--fs-6);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--grey);
}

.page-about .ab-figure--banner {
  margin-bottom: calc(var(--unit) * 7);
}

/* ---------- 04 浅色审校区 ---------- */
.page-about .ab-paper {
  position: relative;
  background: var(--paper);
  color: var(--ink-text);
  padding: calc(var(--unit) * 14) 0 calc(var(--unit) * 14);
}

.page-about .ab-paper::before {
  content: "";
  position: absolute;
  top: -28px;
  left: 0;
  width: 100%;
  height: 28px;
  background: var(--paper);
  clip-path: polygon(0 100%, 100% 0, 100% 100%);
  pointer-events: none;
}

.page-about .ab-paper .ab-figure img {
  border-color: rgba(20, 24, 33, 0.14);
}

.page-about .ab-paper .ab-figure figcaption {
  color: #5B6478;
}

.page-about .ab-head--paper {
  border-bottom-color: rgba(20, 24, 33, 0.16);
}

.page-about .ab-head--paper .ab-head__zh {
  color: var(--ink-text);
}

.page-about .ab-head--paper .ab-head__en {
  color: #5B47C9;
  opacity: 1;
}

.page-about .ab-steps {
  display: grid;
  gap: calc(var(--unit) * 1.5);
}

.page-about .ab-fold {
  background: #FFFFFF;
  border: 1px solid rgba(20, 24, 33, 0.14);
  border-radius: var(--radius);
  overflow: hidden;
}

.page-about .ab-fold__head {
  display: flex;
  align-items: center;
  gap: calc(var(--unit) * 1.5);
  padding: calc(var(--unit) * 2.5) calc(var(--unit) * 3);
  cursor: pointer;
  list-style: none;
  user-select: none;
}

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

.page-about .ab-fold__head:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: -3px;
}

.page-about .ab-fold__idx {
  font-family: var(--font-mono);
  font-size: var(--fs-6);
  letter-spacing: 0.14em;
  color: var(--violet);
  flex: none;
}

.page-about .ab-fold__name {
  font-family: var(--font-cn);
  font-weight: 700;
  font-size: var(--fs-4);
  color: var(--ink-text);
}

.page-about .ab-fold__hint {
  font-family: var(--font-mono);
  font-size: var(--fs-6);
  letter-spacing: 0.1em;
  color: #6A7286;
  flex: none;
}

.page-about .ab-fold__sign {
  position: relative;
  margin-left: auto;
  width: 18px;
  height: 18px;
  flex: none;
}

.page-about .ab-fold__sign::before,
.page-about .ab-fold__sign::after {
  content: "";
  position: absolute;
  background: var(--violet);
  transition: transform 0.22s var(--ease);
}

.page-about .ab-fold__sign::before {
  left: 0;
  top: 8px;
  width: 18px;
  height: 2px;
}

.page-about .ab-fold__sign::after {
  left: 8px;
  top: 0;
  width: 2px;
  height: 18px;
}

.page-about .ab-fold[open] .ab-fold__sign::after {
  transform: scaleY(0);
}

.page-about .ab-fold__body {
  padding: 0 calc(var(--unit) * 3) calc(var(--unit) * 3);
}

.page-about .ab-fold__body p {
  margin: 0;
  font-size: var(--fs-5);
  line-height: 1.85;
  color: #3D4454;
}

.page-about .ab-team {
  display: grid;
  gap: calc(var(--unit) * 5);
  margin-top: calc(var(--unit) * 8);
  padding-top: calc(var(--unit) * 6);
  border-top: 1px solid rgba(20, 24, 33, 0.16);
}

.page-about .ab-team__num {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--fs-2);
  font-weight: 700;
  line-height: 1;
  color: var(--violet);
  font-variant-numeric: tabular-nums;
}

.page-about .ab-team__unit {
  display: block;
  margin-top: calc(var(--unit) * 1.2);
  font-family: var(--font-mono);
  font-size: var(--fs-6);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: #6A7286;
}

.page-about .ab-team__list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .ab-team__list li {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: calc(var(--unit) * 2);
  padding: calc(var(--unit) * 1.6) 0;
  border-bottom: 1px solid rgba(20, 24, 33, 0.12);
  font-size: var(--fs-5);
  color: #3D4454;
}

.page-about .ab-team__list li:first-child {
  border-top: 1px solid rgba(20, 24, 33, 0.12);
}

.page-about .ab-team__count {
  font-family: var(--font-mono);
  font-size: var(--fs-4);
  font-weight: 700;
  color: var(--ink-text);
  font-variant-numeric: tabular-nums;
}

/* ---------- 05 时间线 ---------- */
.page-about .ab-timeline {
  display: grid;
  gap: calc(var(--unit) * 6);
}

.page-about .ab-track {
  list-style: none;
  margin: 0;
  padding: 0;
  position: relative;
}

.page-about .ab-track::before {
  content: "";
  position: absolute;
  left: 3px;
  top: 10px;
  bottom: 10px;
  width: 1px;
  background: linear-gradient(180deg, var(--violet) 0%, var(--cyan) 100%);
}

.page-about .ab-track__item {
  position: relative;
  padding-left: calc(var(--unit) * 4.5);
  padding-bottom: calc(var(--unit) * 4);
}

.page-about .ab-track__item::before {
  content: "";
  position: absolute;
  left: 0;
  top: 7px;
  width: 6px;
  height: 6px;
  background: var(--violet);
  border: 1px solid var(--cyan);
  z-index: 1;
}

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

.page-about .ab-node__head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: calc(var(--unit) * 1.5);
  cursor: pointer;
  list-style: none;
  padding-bottom: calc(var(--unit) * 0.5);
}

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

.page-about .ab-node__head:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 3px;
}

.page-about .ab-node__year {
  font-family: var(--font-mono);
  font-size: var(--fs-5);
  letter-spacing: 0.12em;
  color: var(--amber);
  font-variant-numeric: tabular-nums;
}

.page-about .ab-node__title {
  font-family: var(--font-cn);
  font-weight: 900;
  font-size: var(--fs-4);
  letter-spacing: -0.01em;
  color: var(--white);
}

.page-about .ab-node__sign {
  position: relative;
  align-self: center;
  width: 14px;
  height: 14px;
  flex: none;
}

.page-about .ab-node__sign::before,
.page-about .ab-node__sign::after {
  content: "";
  position: absolute;
  background: var(--grey);
  transition: transform 0.22s var(--ease);
}

.page-about .ab-node__sign::before {
  left: 0;
  top: 6px;
  width: 14px;
  height: 1px;
}

.page-about .ab-node__sign::after {
  left: 6px;
  top: 0;
  width: 1px;
  height: 14px;
}

.page-about .ab-node[open] .ab-node__sign::after {
  transform: scaleY(0);
}

.page-about .ab-node[open] .ab-node__sign::before {
  background: var(--cyan);
}

.page-about .ab-node__body {
  padding-top: calc(var(--unit) * 1.5);
  max-width: 54ch;
}

.page-about .ab-node__body p {
  margin: 0;
  font-family: var(--font-serif);
  font-size: var(--fs-5);
  line-height: 1.9;
  color: var(--grey);
}

/* ---------- 06 收束双栏 ---------- */
.page-about .ab-paths {
  display: grid;
  gap: calc(var(--unit) * 4);
}

.page-about .ab-path {
  position: relative;
  padding: calc(var(--unit) * 4) 0 0;
  border-top: 1px solid var(--line);
}

.page-about .ab-path--first {
  border-top-color: var(--violet);
}

.page-about .ab-path--return {
  border-top-color: var(--cyan);
}

.page-about .ab-path__tag {
  margin: 0 0 calc(var(--unit) * 2);
  font-family: var(--font-mono);
  font-size: var(--fs-6);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--grey);
}

.page-about .ab-path__title {
  margin: 0 0 calc(var(--unit) * 2);
  font-family: var(--font-cn);
  font-weight: 900;
  font-size: var(--fs-4);
  line-height: 1.3;
  color: var(--white);
}

.page-about .ab-path__body {
  margin: 0 0 calc(var(--unit) * 3);
  max-width: 42ch;
  font-size: var(--fs-5);
  line-height: 1.85;
  color: var(--grey);
}

.page-about .ab-path__links {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: calc(var(--unit) * 2.5);
  margin: 0;
}

.page-about .ab-path__more {
  font-family: var(--font-mono);
  font-size: var(--fs-6);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--cyan);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.2s var(--ease);
}

.page-about .ab-path__more:hover,
.page-about .ab-path__more:focus-visible {
  border-bottom-color: var(--cyan);
}

/* ---------- 响应式 ---------- */
@media (min-width: 760px) {
  .page-about .ab-team {
    grid-template-columns: 4fr 8fr;
    gap: calc(var(--unit) * 8);
    align-items: start;
  }

  .page-about .ab-paths {
    grid-template-columns: 1fr 1fr;
    gap: calc(var(--unit) * 8);
  }

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

@media (min-width: 960px) {
  .page-about .about-hero__inner {
    grid-template-columns: 7fr 4fr;
    gap: calc(var(--unit) * 10);
    align-items: end;
  }

  .page-about .ab-split {
    grid-template-columns: 4fr 8fr;
    gap: calc(var(--unit) * 8);
  }

  .page-about .ab-dual {
    grid-template-columns: 1fr 1fr;
    gap: 0;
  }

  .page-about .ab-dual__col {
    padding-right: calc(var(--unit) * 6);
  }

  .page-about .ab-dual__col + .ab-dual__col {
    border-left: 1px solid var(--line);
    padding-left: calc(var(--unit) * 6);
    padding-right: 0;
  }

  .page-about .ab-columns {
    grid-template-columns: 7fr 5fr;
    gap: calc(var(--unit) * 8);
    align-items: start;
  }

  .page-about .ab-timeline {
    grid-template-columns: 4fr 8fr;
    gap: calc(var(--unit) * 10);
    align-items: start;
  }

  .page-about .ab-timeline__media {
    position: sticky;
    top: calc(var(--unit) * 14);
  }

  .page-about .ab-columns__media {
    margin-top: calc(var(--unit) * 3);
  }
}

@media (min-width: 1200px) {
  .page-about .ab-col-item {
    grid-template-columns: 56px 1fr;
    gap: calc(var(--unit) * 3);
  }
}

/* ---------- 动效降级 ---------- */
@media (prefers-reduced-motion: reduce) {
  .page-about .breadcrumb a,
  .page-about .about-index__link,
  .page-about .ab-fold__sign::before,
  .page-about .ab-fold__sign::after,
  .page-about .ab-node__sign::before,
  .page-about .ab-node__sign::after,
  .page-about .ab-path__more {
    transition: none;
  }
}
</main>