.page-about {
  --ab-body: rgba(244, 247, 246, .74);
  --ab-tl-gap: clamp(18px, 2.5vw, 28px);
  --ab-sticky-top: calc(var(--mk-header-h) + 84px);

  position: relative;
  isolation: isolate;
  overflow-x: clip;
  background-color: var(--mk-ink);
  background-image:
    radial-gradient(880px 520px at 10% -6%, rgba(70, 227, 208, .10), transparent 70%),
    radial-gradient(760px 560px at 98% 6%, rgba(224, 160, 41, .07), transparent 72%);
  background-repeat: no-repeat;
  color: var(--mk-cold);
}

.page-about::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 540px;
  z-index: -1;
  pointer-events: none;
  background-image:
    linear-gradient(to right, var(--mk-line-soft) 1px, transparent 1px),
    linear-gradient(to bottom, var(--mk-line-soft) 1px, transparent 1px);
  background-size: 96px 96px;
  -webkit-mask-image: linear-gradient(to bottom, #000, transparent);
  mask-image: linear-gradient(to bottom, #000, transparent);
  opacity: .6;
}

/* 面包屑区留白 */
.page-about .ab-crumbwrap {
  padding-top: clamp(72px, 9vw, 100px);
}

/* 题头 */
.page-about .ab-intro {
  padding-block: clamp(26px, 4vw, 52px) clamp(34px, 5.5vw, 68px);
}

.page-about .ab-intro__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(28px, 4vw, 52px);
  align-items: end;
}

.page-about .ab-intro__title {
  margin: clamp(12px, 1.6vw, 20px) 0 0;
  font-size: clamp(30px, 5.4vw, 56px);
  line-height: 1.1;
  letter-spacing: -.012em;
  max-width: 20em;
}

.page-about .ab-intro__lede {
  margin-top: clamp(16px, 2vw, 24px);
  max-width: 34em;
  color: var(--ab-body);
  font-size: clamp(15px, 1.5vw, 17px);
  line-height: 1.75;
}

.page-about .ab-facts {
  margin: 0;
  border-top: 1px solid var(--mk-line);
}

.page-about .ab-facts__row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  padding: 12px 0;
  border-bottom: 1px solid var(--mk-line-soft);
}

.page-about .ab-facts dt {
  color: var(--mk-sage);
  font-size: 13px;
  letter-spacing: .05em;
}

.page-about .ab-facts dd {
  margin: 0;
  color: var(--mk-cold);
  font-size: clamp(20px, 2.4vw, 26px);
  line-height: 1.1;
}

.page-about .ab-facts__unit {
  margin-left: 3px;
  font-size: 12px;
  color: var(--mk-sage);
  letter-spacing: .04em;
}

/* 章节索引条 */
.page-about .ab-toc {
  position: sticky;
  top: var(--mk-header-h);
  z-index: 20;
  background: rgba(11, 42, 34, .9);
  border-top: 1px solid var(--mk-line-soft);
  border-bottom: 1px solid var(--mk-line-soft);
}

.page-about .ab-toc__list {
  display: flex;
  gap: 2px;
  margin: 0;
  padding: 0;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: none;
}

.page-about .ab-toc__list::-webkit-scrollbar {
  display: none;
}

.page-about .ab-toc__link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 15px 14px;
  white-space: nowrap;
  color: var(--mk-sage);
  font-size: 13px;
  letter-spacing: .03em;
  text-decoration: none;
  border-bottom: 2px solid transparent;
  transition: color .18s var(--mk-ease), border-color .18s var(--mk-ease);
}

.page-about .ab-toc__link .mk-num {
  font-size: 11px;
  color: var(--mk-sage);
  opacity: .8;
}

.page-about .ab-toc__link:hover {
  color: var(--mk-cold);
}

.page-about .ab-toc__link[aria-current="location"] {
  color: var(--mk-cyan);
  border-bottom-color: var(--mk-cyan);
}

.page-about .ab-toc__link[aria-current="location"] .mk-num {
  color: var(--mk-cyan);
  opacity: 1;
}

/* 章节骨架 */
.page-about .ab-sec {
  padding-block: clamp(42px, 6vw, 82px);
}

.page-about .ab-sec + .ab-sec,
.page-about .ab-closing {
  border-top: 1px solid var(--mk-line-soft);
}

.page-about .ab-sec__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(20px, 3vw, 36px);
}

.page-about .ab-sec__aside {
  display: flex;
  align-items: baseline;
  gap: 12px;
  flex-wrap: wrap;
}

.page-about .ab-sec__title {
  margin: 0;
  font-size: clamp(22px, 3vw, 32px);
  line-height: 1.2;
}

.page-about .ab-sec__kicker {
  margin: 0;
  color: var(--mk-sage);
  font-size: 12px;
  letter-spacing: .06em;
}

.page-about .ab-para {
  margin: 0 0 18px;
  max-width: 38em;
  color: var(--ab-body);
  font-size: clamp(15px, 1.4vw, 16px);
  line-height: 1.8;
}

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

.page-about .ab-inline-link {
  color: var(--mk-cyan);
  text-decoration: none;
  border-bottom: 1px solid rgba(70, 227, 208, .38);
  transition: border-color .18s var(--mk-ease);
}

.page-about .ab-inline-link:hover {
  border-bottom-color: var(--mk-cyan);
}

/* 时间轴 */
.page-about .ab-timeline {
  margin: 26px 0 0;
  padding-left: var(--ab-tl-gap);
  border-left: 1px solid var(--mk-line);
}

.page-about .ab-node {
  position: relative;
  border-bottom: 1px solid var(--mk-line-soft);
}

.page-about .ab-node:first-child {
  border-top: 1px solid var(--mk-line-soft);
}

.page-about .ab-node::before {
  content: "";
  position: absolute;
  top: 21px;
  left: calc(-1 * var(--ab-tl-gap) - 5px);
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--mk-amber);
  box-shadow: 0 0 0 4px rgba(224, 160, 41, .13);
  transition: box-shadow .2s var(--mk-ease);
}

.page-about .ab-node[open]::before {
  box-shadow: 0 0 0 6px rgba(70, 227, 208, .16);
}

.page-about .ab-node__head {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: 12px;
  padding: 13px 14px;
  cursor: pointer;
  list-style: none;
  border-left: 2px solid transparent;
  transition: background-color .18s var(--mk-ease), border-color .18s var(--mk-ease);
}

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

.page-about .ab-node__head:hover {
  background: rgba(70, 227, 208, .05);
}

.page-about .ab-node[open] .ab-node__head {
  border-left-color: var(--mk-cyan);
}

.page-about .ab-node__ver {
  padding: 3px 8px;
  border: 1px solid rgba(224, 160, 41, .42);
  border-radius: 2px;
  color: var(--mk-amber);
  font-size: 12px;
  letter-spacing: .05em;
  white-space: nowrap;
}

.page-about .ab-node__name {
  color: var(--mk-cold);
  font-size: clamp(14px, 1.5vw, 16px);
  line-height: 1.4;
}

.page-about .ab-node__toggle {
  width: 9px;
  height: 9px;
  margin-right: 4px;
  border-right: 1px solid var(--mk-sage);
  border-bottom: 1px solid var(--mk-sage);
  transform: rotate(45deg) translate(-2px, -2px);
  transition: transform .2s var(--mk-ease), border-color .2s var(--mk-ease);
}

.page-about .ab-node[open] .ab-node__toggle {
  border-color: var(--mk-cyan);
  transform: rotate(-135deg) translate(-2px, -2px);
}

.page-about .ab-node__body {
  padding: 2px 14px 18px;
  max-width: 36em;
  color: var(--ab-body);
  font-size: 15px;
  line-height: 1.8;
}

.page-about .ab-node__body p {
  margin: 0;
}

/* 图组 */
.page-about .ab-figure {
  margin: clamp(26px, 3.6vw, 42px) 0 0;
  max-width: 660px;
}

.page-about .ab-figure .mk-media {
  width: 100%;
}

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

.page-about .ab-figure .mk-media__cap {
  display: block;
  margin-top: 10px;
  max-width: 40em;
}

/* 三步顺序 */
.page-about .ab-order {
  margin: 4px 0 0;
  padding: 0;
  list-style: none;
}

.page-about .ab-order__item {
  display: grid;
  grid-template-columns: 42px minmax(0, 1fr);
  gap: 0 14px;
  padding: 16px 0;
  border-top: 1px solid var(--mk-line-soft);
}

.page-about .ab-order__no {
  grid-row: span 2;
  padding-top: 3px;
  color: var(--mk-cyan);
  font-size: 12px;
  letter-spacing: .08em;
}

.page-about .ab-order__title {
  margin: 0 0 6px;
  color: var(--mk-cold);
  font-size: clamp(16px, 1.8vw, 19px);
  font-weight: 600;
  line-height: 1.3;
}

.page-about .ab-order__text {
  margin: 0;
  max-width: 34em;
  color: var(--ab-body);
  font-size: 15px;
  line-height: 1.75;
}

.page-about .ab-callout {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 10px;
  margin: 26px 0 0;
  padding: 16px 18px;
  max-width: 40em;
  border-left: 2px solid var(--mk-alert);
  background: rgba(194, 74, 43, .07);
  color: var(--ab-body);
  font-size: 15px;
  line-height: 1.75;
}

/* 值班时段条 */
.page-about .ab-shifts {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  margin-top: 22px;
  background: var(--mk-line-soft);
  border: 1px solid var(--mk-line-soft);
}

.page-about .ab-shift {
  display: grid;
  grid-template-columns: 52px minmax(0, 1fr);
  align-items: center;
  gap: 14px;
  padding: 18px 16px;
  background: var(--mk-ink-2);
}

.page-about .ab-shift__code {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  border-radius: 50%;
  border: 1px solid rgba(70, 227, 208, .38);
  color: var(--mk-cyan);
  font-size: 15px;
}

.page-about .ab-shift__desc {
  margin: 0;
  color: var(--ab-body);
  font-size: 14px;
  line-height: 1.65;
}

/* 复核流程 */
.page-about .ab-check {
  margin: 26px 0 0;
  padding: 0;
  list-style: none;
}

.page-about .ab-check__item {
  display: grid;
  grid-template-columns: 42px minmax(0, 1fr);
  gap: 0 14px;
  padding: 12px 0;
  border-top: 1px solid var(--mk-line-soft);
}

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

.page-about .ab-check__no {
  color: var(--mk-sage);
  font-size: 12px;
  letter-spacing: .06em;
  padding-top: 3px;
}

.page-about .ab-check__text {
  color: var(--ab-body);
  font-size: 15px;
  line-height: 1.7;
}

/* 覆盖范围数字群 */
.page-about .ab-coverage {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(148px, 1fr));
  gap: 1px;
  margin-bottom: 26px;
  background: var(--mk-line-soft);
  border: 1px solid var(--mk-line-soft);
}

.page-about .ab-coverage__item {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 20px 16px 22px;
  background-color: var(--mk-ink);
  background-image: linear-gradient(160deg, rgba(18, 48, 40, .85), rgba(11, 42, 34, 1));
}

.page-about .ab-coverage__num {
  color: var(--mk-cold);
  font-size: clamp(28px, 4.2vw, 42px);
  line-height: 1;
  letter-spacing: -.02em;
}

.page-about .ab-coverage__plus {
  font-size: .6em;
  color: var(--mk-amber);
  margin-left: 2px;
}

.page-about .ab-coverage__label {
  color: var(--mk-sage);
  font-size: 12px;
  letter-spacing: .04em;
  line-height: 1.5;
}

/* 四个系列 */
.page-about .ab-series {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 0;
}

.page-about .ab-series__item {
  padding: 16px 0;
  border-top: 1px solid var(--mk-line-soft);
}

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

.page-about .ab-series__text {
  margin: 10px 0 0;
  max-width: 36em;
  color: var(--ab-body);
  font-size: 15px;
  line-height: 1.75;
}

/* 收束 */
.page-about .ab-closing {
  padding-block: clamp(38px, 5.5vw, 70px) clamp(56px, 8vw, 96px);
}

.page-about .ab-band {
  margin: 0 0 clamp(28px, 4vw, 44px);
  overflow: hidden;
}

.page-about .ab-band img {
  display: block;
  width: 100%;
  height: clamp(130px, 17vw, 210px);
  object-fit: cover;
  opacity: .42;
}

.page-about .ab-next__title {
  margin: 0 0 18px;
  font-size: clamp(18px, 2.2vw, 22px);
  font-weight: 600;
  line-height: 1.3;
}

.page-about .ab-next__list {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 0;
  padding: 0;
  list-style: none;
}

/* 响应式 */
@media (min-width: 640px) {
  .page-about .ab-series {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    column-gap: clamp(20px, 3vw, 40px);
  }

  .page-about .ab-shifts {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .page-about .ab-shift {
    grid-template-columns: minmax(0, 1fr);
    align-items: start;
    gap: 12px;
  }
}

@media (min-width: 900px) {
  .page-about .ab-sec__grid {
    grid-template-columns: minmax(0, 224px) minmax(0, 1fr);
    gap: clamp(32px, 5vw, 76px);
  }

  .page-about .ab-sec__aside {
    display: block;
    align-self: start;
    position: sticky;
    top: var(--ab-sticky-top);
  }

  .page-about .ab-sec__aside .mk-index {
    display: block;
    margin-bottom: 10px;
  }

  .page-about .ab-sec__title {
    margin-bottom: 10px;
  }

  .page-about .ab-sec__kicker {
    display: block;
  }
}

@media (min-width: 1024px) {
  .page-about .ab-intro__grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 4fr);
    gap: clamp(40px, 5vw, 84px);
  }

  .page-about .ab-facts {
    padding-top: 6px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .ab-node__head,
  .page-about .ab-node__toggle,
  .page-about .ab-toc__link,
  .page-about .ab-inline-link {
    transition: none;
  }
}