.page-about {
  --ab-notch: 18px;
  --ab-rail: 84px;
  display: block;
  padding: clamp(22px, 4vw, 42px) 0 clamp(56px, 8vw, 104px);
  color: var(--text-mid);
  font-family: var(--font-body);
  background:
    radial-gradient(88% 52% at 94% -6%, rgba(122, 59, 255, .22), transparent 62%),
    radial-gradient(66% 44% at -8% 40%, rgba(31, 224, 208, .10), transparent 62%);
}

/* ---------- 首屏 ---------- */
.page-about .ab-hero {
  display: grid;
  gap: 22px;
  margin-bottom: clamp(26px, 4vw, 42px);
}

.page-about .ab-hero__title {
  margin: 12px 0 16px;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(38px, 6vw, 76px);
  line-height: 1.04;
  letter-spacing: -.02em;
  color: var(--text-high);
}

.page-about .ab-hero__title-line {
  display: block;
}

.page-about .ab-hero__title-line--em {
  color: var(--cyan-neon);
  text-shadow: 0 0 26px rgba(31, 224, 208, .28);
}

.page-about .ab-hero__lead {
  margin: 0;
  max-width: 60ch;
  font-size: clamp(15px, 1.6vw, 17px);
  line-height: 1.8;
  color: var(--text-mid);
}

.page-about .ab-hero__stats {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
  margin: 24px 0 0;
  padding-top: 18px;
  border-top: 1px solid var(--line-soft);
}

.page-about .ab-hero__stats dt {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: .1em;
  color: var(--text-low);
}

.page-about .ab-hero__stats dd {
  margin: 7px 0 0;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(15px, 2.1vw, 21px);
  line-height: 1.1;
  color: var(--text-high);
}

.page-about .ab-hero__rail {
  padding: 22px 20px 24px;
  background:
    repeating-linear-gradient(108deg, rgba(122, 59, 255, .07) 0 1px, transparent 1px 15px),
    linear-gradient(155deg, rgba(30, 38, 80, .92), rgba(14, 18, 41, .78));
  box-shadow:
    inset 0 0 0 1px var(--line-hair),
    inset 0 0 0 2px rgba(31, 224, 208, .07),
    0 26px 60px -34px rgba(58, 28, 140, .95);
  clip-path: polygon(0 0, calc(100% - var(--ab-notch)) 0, 100% var(--ab-notch), 100% 100%, 0 100%);
}

.page-about .ab-hero__rail-label {
  margin: 0 0 16px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: .2em;
  color: var(--cyan-neon);
}

.page-about .ab-hero__rules {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 12px;
}

.page-about .ab-hero__rule {
  display: grid;
  grid-template-columns: 28px minmax(0, 1fr);
  gap: 10px;
  padding-bottom: 12px;
  font-size: 14.5px;
  line-height: 1.7;
  color: var(--text-mid);
  border-bottom: 1px dashed var(--line-soft);
}

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

.page-about .ab-hero__rule-idx {
  font-family: var(--font-mono);
  font-size: 12.5px;
  font-weight: 700;
  color: var(--violet-soft);
}

/* ---------- 目录条 ---------- */
.page-about .ab-index {
  display: grid;
  gap: 10px;
  margin: 0 0 clamp(28px, 4vw, 48px);
  padding: 12px 0;
  border-top: 1px solid var(--line-soft);
  border-bottom: 1px solid var(--line-soft);
}

.page-about .ab-index__title {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: .2em;
  color: var(--text-low);
}

.page-about .ab-index__list {
  display: flex;
  gap: 8px;
  margin: 0;
  padding: 2px 0;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: thin;
}

.page-about .ab-index__list li {
  flex: 0 0 auto;
}

.page-about .ab-index__link {
  display: inline-flex;
  align-items: center;
  min-height: 38px;
  padding: 6px 13px;
  font-size: 13.5px;
  white-space: nowrap;
  text-decoration: none;
  color: var(--text-mid);
  background: rgba(22, 28, 60, .62);
  border: 1px solid var(--line-soft);
  clip-path: polygon(0 0, calc(100% - 10px) 0, 100% 10px, 100% 100%, 0 100%);
  transition: color var(--dur) var(--ease), background-color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}

.page-about .ab-index__link:hover,
.page-about .ab-index__link:focus-visible {
  color: var(--text-high);
  border-color: var(--cyan-neon);
}

.page-about .ab-index__link[data-current="true"] {
  color: var(--bg-base);
  font-weight: 700;
  background: var(--cyan-neon);
  border-color: var(--cyan-neon);
}

/* ---------- 区块骨架 ---------- */
.page-about .ab-block {
  display: grid;
  gap: 14px;
  padding: clamp(28px, 5vw, 56px) 0;
  border-top: 1px solid var(--line-soft);
}

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

.page-about .ab-block__note .vertical-note {
  display: inline-block;
  padding-bottom: 8px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: .16em;
  color: var(--violet-soft);
  border-bottom: 1px solid var(--line-hair);
}

/* ---------- 媒体框 ---------- */
.page-about .ab-figure {
  margin: 24px 0 0;
}

.page-about .ab-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  background: var(--bg-panel);
  box-shadow: inset 0 0 0 1px var(--line-hair);
}

/* ---------- 业务线分栏 ---------- */
.page-about .ab-split {
  display: grid;
  gap: 16px;
  margin-top: 22px;
}

.page-about .ab-line {
  position: relative;
  padding: 22px 20px 20px;
  background:
    repeating-linear-gradient(104deg, rgba(122, 59, 255, .07) 0 1px, transparent 1px 14px),
    linear-gradient(160deg, rgba(22, 28, 60, .95), rgba(14, 18, 41, .82));
  box-shadow: inset 0 0 0 1px var(--line-hair), inset 3px 0 0 0 var(--cyan-neon);
  clip-path: polygon(0 0, calc(100% - var(--ab-notch)) 0, 100% var(--ab-notch), 100% 100%, 0 100%);
}

.page-about .ab-line--violet {
  box-shadow: inset 0 0 0 1px var(--line-hair), inset 3px 0 0 0 var(--violet-core);
}

.page-about .ab-line__tag {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: .16em;
  color: var(--cyan-neon);
}

.page-about .ab-line--violet .ab-line__tag {
  color: var(--violet-soft);
}

.page-about .ab-line__title {
  margin: 0 0 14px;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 22px;
  line-height: 1.25;
  color: var(--text-high);
}

.page-about .ab-line__list {
  list-style: none;
  margin: 0 0 14px;
  padding: 0;
  display: grid;
  gap: 9px;
}

.page-about .ab-line__list li {
  position: relative;
  padding-left: 16px;
  font-size: 15px;
  line-height: 1.72;
  color: var(--text-mid);
}

.page-about .ab-line__list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: .68em;
  width: 7px;
  height: 7px;
  background: var(--cyan-neon);
  clip-path: polygon(0 0, 100% 0, 100% 100%);
}

.page-about .ab-line--violet .ab-line__list li::before {
  background: var(--violet-core);
}

.page-about .ab-line__link {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding: 0 0 3px;
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--text-high);
  text-decoration: none;
  border-bottom: 1px solid var(--violet-core);
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}

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

/* ---------- 版本号读法 ---------- */
.page-about .ab-notation {
  display: grid;
  gap: 16px;
  margin-top: 22px;
}

.page-about .ab-notation__card {
  padding: 24px 22px 26px;
  background: linear-gradient(160deg, rgba(22, 28, 60, .96), rgba(14, 18, 41, .78));
  box-shadow: inset 0 0 0 1px var(--line-hair);
  clip-path: polygon(0 0, calc(100% - var(--ab-notch)) 0, 100% var(--ab-notch), 100% 100%, 0 100%);
}

.page-about .ab-notation__card--accent {
  background: linear-gradient(150deg, rgba(122, 59, 255, .26), rgba(22, 28, 60, .92) 62%);
  clip-path: polygon(0 0, 100% 0, 100% 100%, calc(100% - var(--ab-notch)) 100%, 0 calc(100% - var(--ab-notch)));
}

.page-about .ab-notation__sample {
  margin: 0 0 12px;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(34px, 6vw, 54px);
  line-height: 1;
  letter-spacing: -.02em;
  color: var(--text-high);
}

.page-about .ab-notation__card--accent .ab-notation__sample {
  color: var(--cyan-neon);
  text-shadow: 0 0 24px rgba(31, 224, 208, .3);
}

.page-about .ab-notation__name {
  margin: 0 0 10px;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 18px;
  color: var(--text-high);
}

.page-about .ab-notation__desc {
  margin: 0;
  max-width: 46ch;
  font-size: 15px;
  line-height: 1.78;
  color: var(--text-mid);
}

.page-about .ab-rule-strip {
  margin-top: 20px;
  padding: 18px 20px;
  border-left: 3px solid var(--violet-core);
  background: linear-gradient(90deg, rgba(122, 59, 255, .16), rgba(122, 59, 255, 0) 72%);
}

.page-about .ab-rule-strip__text {
  margin: 0;
  max-width: 64ch;
  font-size: 15.5px;
  line-height: 1.78;
  color: var(--text-mid);
}

/* ---------- 配置四档 ---------- */
.page-about .ab-tiers {
  list-style: none;
  margin: 24px 0 0;
  padding: 0;
  display: grid;
  gap: 10px;
  counter-reset: none;
}

.page-about .ab-tiers__item {
  display: grid;
  gap: 6px;
  padding: 18px 16px 20px;
  background: linear-gradient(180deg, rgba(30, 38, 80, .82), rgba(14, 18, 41, .48));
  border-top: 3px solid var(--violet-core);
  border-left: 1px solid var(--line-soft);
  border-right: 1px solid var(--line-soft);
  border-bottom: 1px solid var(--line-soft);
}

.page-about .ab-tiers__item:nth-child(1) { border-top-color: rgba(122, 59, 255, .45); }
.page-about .ab-tiers__item:nth-child(2) { border-top-color: var(--violet-core); }
.page-about .ab-tiers__item:nth-child(3) { border-top-color: var(--violet-soft); }
.page-about .ab-tiers__item:nth-child(4) { border-top-color: var(--cyan-neon); }

.page-about .ab-tiers__idx {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .14em;
  color: var(--text-low);
}

.page-about .ab-tiers__name {
  margin: 2px 0 0;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 18px;
  color: var(--text-high);
}

.page-about .ab-tiers__span {
  margin: 0;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 15px;
  letter-spacing: .02em;
  color: var(--cyan-neon);
}

.page-about .ab-tiers__desc {
  margin: 4px 0 0;
  font-size: 14px;
  line-height: 1.72;
  color: var(--text-mid);
}

/* ---------- 时间线 ---------- */
.page-about .ab-timeline {
  list-style: none;
  margin: 26px 0 0;
  padding: 0;
}

.page-about .ab-timeline__node {
  position: relative;
  padding: 22px 16px 22px 26px;
  border-left: 2px solid var(--line-hair);
  outline: none;
}

.page-about .ab-timeline__dot {
  position: absolute;
  top: 28px;
  left: -7px;
  width: 12px;
  height: 12px;
  background: var(--cyan-neon);
  clip-path: polygon(50% 0, 100% 50%, 50% 100%, 0 50%);
  transition: transform var(--dur) var(--ease);
}

.page-about .ab-timeline__node:hover .ab-timeline__dot,
.page-about .ab-timeline__node:focus-visible .ab-timeline__dot,
.page-about .ab-timeline__node:focus-within .ab-timeline__dot {
  transform: scale(1.4);
}

.page-about .ab-timeline__ver {
  margin: 0;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(24px, 3vw, 32px);
  line-height: 1;
  letter-spacing: -.02em;
  color: var(--text-high);
}

.page-about .ab-timeline__era {
  margin: 8px 0 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .06em;
  color: var(--text-low);
}

.page-about .ab-timeline__desc {
  margin: 10px 0 0;
  font-size: 14px;
  line-height: 1.72;
  color: var(--text-mid);
}

.page-about .ab-timeline__more {
  max-height: 0;
  margin: 0;
  padding-top: 0;
  overflow: hidden;
  opacity: 0;
  font-size: 13px;
  line-height: 1.68;
  color: var(--violet-soft);
  border-top: 1px dashed transparent;
  transition: max-height var(--dur-slow) var(--ease), opacity var(--dur) var(--ease), padding var(--dur) var(--ease);
}

.page-about .ab-timeline__node:hover .ab-timeline__more,
.page-about .ab-timeline__node:focus-within .ab-timeline__more {
  max-height: 200px;
  padding-top: 10px;
  opacity: 1;
  border-top-color: var(--line-soft);
}

@media (hover: none) {
  .page-about .ab-timeline__more {
    max-height: none;
    padding-top: 10px;
    opacity: 1;
    border-top-color: var(--line-soft);
  }
}

/* ---------- 维护节奏 ---------- */
.page-about .ab-cadence {
  list-style: none;
  margin: 24px 0 0;
  padding: 0;
  display: grid;
  gap: 10px;
}

.page-about .ab-cadence__row {
  display: grid;
  gap: 8px;
  padding: 14px 16px;
  background: var(--bg-panel);
  border-left: 3px solid var(--violet-core);
  align-items: center;
}

.page-about .ab-cadence__row:nth-child(1) { border-left-color: var(--state-ok); }
.page-about .ab-cadence__row:nth-child(2) { border-left-color: var(--cyan-neon); }
.page-about .ab-cadence__row:nth-child(3) { border-left-color: var(--violet-soft); }
.page-about .ab-cadence__row:nth-child(4) { border-left-color: var(--amber-warm); }

.page-about .ab-cadence__key {
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: .06em;
  color: var(--cyan-neon);
}

.page-about .ab-cadence__val {
  font-size: 14.5px;
  line-height: 1.72;
  color: var(--text-mid);
}

.page-about .ab-cadence__row .tag {
  justify-self: start;
}

/* ---------- 口径边界 ---------- */
.page-about .ab-boundary {
  display: grid;
  gap: 16px;
  margin-top: 22px;
}

.page-about .ab-boundary__col {
  padding: 22px 20px 24px;
  background: linear-gradient(160deg, rgba(22, 28, 60, .94), rgba(14, 18, 41, .72));
  box-shadow: inset 0 0 0 1px var(--line-hair);
}

.page-about .ab-boundary__col--stop {
  background: linear-gradient(160deg, rgba(255, 162, 58, .10), rgba(14, 18, 41, .74));
  box-shadow: inset 0 0 0 1px rgba(255, 162, 58, .3);
}

.page-about .ab-boundary__title {
  margin: 0 0 14px;
  padding-bottom: 10px;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 18px;
  color: var(--text-high);
  border-bottom: 1px solid var(--line-soft);
}

.page-about .ab-boundary__col--stop .ab-boundary__title {
  color: var(--amber-warm);
  border-bottom-color: rgba(255, 162, 58, .3);
}

.page-about .ab-boundary__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 10px;
}

.page-about .ab-boundary__list li {
  position: relative;
  padding-left: 22px;
  font-size: 14.5px;
  line-height: 1.74;
  color: var(--text-mid);
}

.page-about .ab-boundary__list li::before {
  content: "＋";
  position: absolute;
  left: 0;
  top: 0;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.95;
  color: var(--cyan-neon);
}

.page-about .ab-boundary__col--stop .ab-boundary__list li::before {
  content: "－";
  color: var(--amber-warm);
}

.page-about .ab-details {
  margin-top: 20px;
  background: var(--bg-panel);
  box-shadow: inset 0 0 0 1px var(--line-soft);
}

.page-about .ab-details__summary {
  display: flex;
  align-items: center;
  gap: 10px;
  min-height: 52px;
  padding: 14px 20px;
  font-family: var(--font-mono);
  font-size: 13.5px;
  letter-spacing: .04em;
  color: var(--text-high);
  cursor: pointer;
  list-style: none;
}

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

.page-about .ab-details__summary::before {
  content: "▸";
  color: var(--cyan-neon);
  font-size: 13px;
  transition: transform var(--dur) var(--ease);
}

.page-about .ab-details[open] .ab-details__summary::before {
  transform: rotate(90deg);
}

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

.page-about .ab-details__body {
  display: grid;
  gap: 12px;
  padding: 0 20px 22px;
}

.page-about .ab-details__body p {
  margin: 0;
  max-width: 68ch;
  font-size: 14.5px;
  line-height: 1.8;
  color: var(--text-mid);
}

.page-about .ab-note-bar {
  display: grid;
  gap: 8px;
  margin-top: 24px;
  padding: 18px 20px;
  background: linear-gradient(96deg, rgba(31, 224, 208, .13), rgba(122, 59, 255, .11) 56%, rgba(255, 162, 58, .08));
  box-shadow: inset 0 0 0 1px var(--line-hair);
}

.page-about .ab-note-bar__label {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: .2em;
  color: var(--cyan-neon);
}

.page-about .ab-note-bar__text {
  margin: 0;
  max-width: 70ch;
  font-size: 14.5px;
  line-height: 1.78;
  color: var(--text-mid);
}

/* ---------- 延伸入口 ---------- */
.page-about .ab-next {
  list-style: none;
  margin: 22px 0 0;
  padding: 0;
  display: grid;
  gap: 10px;
}

.page-about .ab-next__link {
  display: grid;
  gap: 5px;
  min-height: 44px;
  padding: 16px 18px;
  text-decoration: none;
  background: rgba(22, 28, 60, .7);
  box-shadow: inset 0 0 0 1px var(--line-soft);
  clip-path: polygon(0 0, calc(100% - 14px) 0, 100% 14px, 100% 100%, 0 100%);
  transition: background-color var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}

.page-about .ab-next__link:hover,
.page-about .ab-next__link:focus-visible {
  background: var(--bg-panel-raise);
  box-shadow: inset 0 0 0 1px var(--cyan-neon);
}

.page-about .ab-next__name {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 16px;
  color: var(--text-high);
}

.page-about .ab-next__desc {
  font-size: 13.5px;
  line-height: 1.68;
  color: var(--text-low);
}

/* ---------- 桌面栅格 ---------- */
@media (min-width: 700px) {
  .page-about .ab-notation {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 20px;
  }

  .page-about .ab-boundary {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 20px;
  }

  .page-about .ab-next {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 12px;
  }

  .page-about .ab-cadence__row {
    grid-template-columns: 108px minmax(0, 1fr) auto;
    gap: 18px;
  }

  .page-about .ab-note-bar {
    grid-template-columns: 92px minmax(0, 1fr);
    gap: 18px;
    align-items: baseline;
  }

  .page-about .ab-index {
    grid-template-columns: auto minmax(0, 1fr);
    align-items: center;
    gap: 20px;
  }
}

@media (min-width: 760px) {
  .page-about .ab-split {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 20px;
  }
}

@media (min-width: 900px) {
  .page-about .ab-tiers {
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 0;
  }

  .page-about .ab-tiers__item {
    border-right: 0;
  }

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

  .page-about .ab-timeline {
    display: grid;
    grid-template-columns: repeat(5, minmax(0, 1fr));
  }

  .page-about .ab-timeline__node {
    padding: 24px 16px 26px;
    border-left: 0;
    border-top: 2px solid var(--line-hair);
  }

  .page-about .ab-timeline__dot {
    top: -7px;
    left: 16px;
  }
}

@media (min-width: 960px) {
  .page-about .ab-hero {
    grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
    gap: 32px;
    align-items: end;
  }
}

@media (min-width: 1000px) {
  .page-about .ab-block {
    grid-template-columns: var(--ab-rail) minmax(0, 1fr);
    gap: 36px;
    align-items: start;
  }

  .page-about .ab-block__note {
    position: sticky;
    top: calc(var(--header-h) + 30px);
    display: flex;
    justify-content: center;
  }

  .page-about .ab-block__note .vertical-note {
    writing-mode: vertical-rl;
    padding: 0 0 0 10px;
    padding-bottom: 0;
    border-bottom: 0;
    border-left: 1px solid var(--line-hair);
    max-height: 230px;
  }
}

/* ---------- 动效降级 ---------- */
@media (prefers-reduced-motion: reduce) {
  .page-about .ab-timeline__dot,
  .page-about .ab-timeline__more,
  .page-about .ab-details__summary::before,
  .page-about .ab-next__link,
  .page-about .ab-index__link,
  .page-about .ab-line__link {
    transition-duration: .001ms !important;
  }

  .page-about .ab-timeline__node:hover .ab-timeline__dot,
  .page-about .ab-timeline__node:focus-within .ab-timeline__dot {
    transform: none;
  }
}