.page-about {
  --ab-year: 104px;
  --ab-ink-soft: #3B4553;
  --ab-ink-faint: #6E7887;
  --ab-line-soft: rgba(11, 18, 32, 0.14);
  background-color: var(--ink);
  color: var(--silver);
  font-family: var(--font-body);
  overflow-x: clip;
}

.page-about section[id] {
  scroll-margin-top: 104px;
}

/* ---------- 首屏 ---------- */
.ab-hero {
  padding-block: clamp(22px, 4vw, 40px) clamp(38px, 6vw, 76px);
  background-color: var(--ink);
  background-image:
    radial-gradient(118% 82% at 92% -18%, rgba(47, 227, 206, 0.14), transparent 62%),
    linear-gradient(180deg, rgba(22, 32, 46, 0.72), rgba(11, 18, 32, 0) 72%);
}

.ab-hero__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(26px, 5vw, 56px);
  margin-top: clamp(22px, 4vw, 40px);
}

.ab-hero__eyebrow {
  margin: 0 0 16px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.2em;
  color: var(--cyan);
}

.ab-hero__title {
  margin: 0 0 clamp(16px, 2.4vw, 26px);
  font-family: var(--font-display);
  font-weight: 200;
  font-size: clamp(31px, 6.1vw, 66px);
  line-height: 1.14;
  letter-spacing: 0.02em;
  color: var(--paper);
  max-width: 15em;
}

.ab-hero__text {
  margin: 0 0 clamp(22px, 3vw, 34px);
  font-size: clamp(15px, 1.5vw, 17px);
  line-height: 1.85;
  color: var(--silver);
  max-width: 33em;
}

.ab-hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.ab-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  background-color: var(--line);
  border: 1px solid var(--line);
  border-radius: 3px;
  overflow: hidden;
}

.ab-stats__item {
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: clamp(14px, 2.2vw, 22px);
  background-color: var(--rock);
}

.ab-stats__item::before {
  content: "";
  display: block;
  width: 22px;
  height: 1px;
  background-color: var(--cyan);
}

.ab-stats__num {
  font-family: var(--font-mono);
  font-size: clamp(24px, 3.2vw, 34px);
  line-height: 1;
  letter-spacing: 0.02em;
  color: var(--paper);
}

.ab-stats__label {
  font-size: 12px;
  line-height: 1.6;
  letter-spacing: 0.04em;
  color: var(--frost);
}

/* ---------- 章节索引 ---------- */
.ab-index {
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  margin-top: clamp(26px, 4vw, 46px);
}

.ab-index__list {
  display: flex;
  flex-wrap: wrap;
  gap: 0 clamp(16px, 3vw, 40px);
  margin: 0;
  padding: 0;
  list-style: none;
}

.ab-index__link {
  display: inline-flex;
  align-items: baseline;
  gap: 8px;
  padding: 14px 0;
  font-size: 13px;
  letter-spacing: 0.02em;
  color: var(--frost);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color var(--t), border-color var(--t);
}

.ab-index__link:hover,
.ab-index__link:focus-visible {
  color: var(--paper);
  border-bottom-color: var(--cyan);
}

.ab-index__no {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  color: var(--clay);
}

/* ---------- 通用章节 ---------- */
.ab-sec {
  padding-block: clamp(42px, 7vw, 88px);
  border-top: 1px solid var(--line);
}

.ab-sec--paper {
  background-color: var(--paper);
  color: var(--ab-ink-soft);
  border-top-color: var(--ab-line-soft);
}

.ab-sec__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(14px, 2.4vw, 22px);
}

.ab-sec__rail {
  display: flex;
  align-items: baseline;
  gap: 12px;
}

.ab-sec__no {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--clay);
}

.ab-sec__year {
  font-family: var(--font-mono);
  font-size: clamp(20px, 2.6vw, 28px);
  line-height: 1;
  letter-spacing: 0.05em;
  color: var(--silver);
}

.ab-sec--paper .ab-sec__year {
  color: var(--ink);
}

.ab-sec__title {
  margin: 0 0 clamp(14px, 2.2vw, 24px);
  font-family: var(--font-display);
  font-weight: 300;
  font-size: clamp(24px, 3.4vw, 38px);
  line-height: 1.25;
  letter-spacing: 0.02em;
  color: var(--paper);
}

.ab-sec--paper .ab-sec__title {
  color: var(--ink);
}

.ab-sec__text {
  margin: 0 0 1.1em;
  font-size: clamp(15px, 1.5vw, 17px);
  line-height: 1.9;
  max-width: 36em;
  color: var(--silver);
}

.ab-sec__text:last-child {
  margin-bottom: 0;
}

.ab-sec--paper .ab-sec__text {
  color: var(--ab-ink-soft);
}

/* ---------- 图片 ---------- */
.ab-figure {
  margin: 0 0 clamp(20px, 3vw, 32px);
}

.ab-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  border: 1px solid var(--line);
  border-radius: 3px;
  background-color: var(--rock);
}

.ab-sec--paper .ab-figure img {
  border-color: var(--ab-line-soft);
  background-color: rgba(11, 18, 32, 0.05);
}

.ab-figure__cap {
  margin-top: 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.06em;
  line-height: 1.7;
  color: var(--frost);
}

.ab-sec--paper .ab-figure__cap {
  color: var(--ab-ink-faint);
}

/* ---------- 年份轴 ---------- */
.ab-tl__list {
  margin: clamp(20px, 3vw, 30px) 0 0;
  padding: 0;
  list-style: none;
}

.ab-tl__item {
  position: relative;
  padding: 0 0 clamp(22px, 3vw, 30px) 26px;
  border-left: 1px solid var(--line);
}

.ab-tl__item:last-child {
  padding-bottom: 0;
  border-left-color: transparent;
}

.ab-tl__dot {
  position: absolute;
  left: -4.5px;
  top: 6px;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: var(--line);
  transition: background-color var(--t), box-shadow var(--t);
}

.ab-tl__item:hover .ab-tl__dot,
.ab-tl__item:focus-within .ab-tl__dot {
  background-color: var(--cyan);
  box-shadow: 0 0 0 4px rgba(47, 227, 206, 0.18);
}

.ab-tl__year {
  display: block;
  margin-bottom: 8px;
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.14em;
  color: var(--frost);
  transition: color var(--t);
}

.ab-tl__item:hover .ab-tl__year,
.ab-tl__item:focus-within .ab-tl__year {
  color: var(--cyan);
}

.ab-tl__card {
  padding: clamp(14px, 2vw, 20px) clamp(16px, 2.2vw, 24px);
  background-color: var(--rock);
  border: 1px solid var(--line);
  border-radius: 3px;
  transition: border-color var(--t), transform var(--t);
}

.ab-tl__item:hover .ab-tl__card,
.ab-tl__item:focus-within .ab-tl__card {
  border-color: var(--cyan);
  transform: translateX(2px);
}

.ab-tl__title {
  margin: 0 0 8px;
  font-size: clamp(16px, 1.7vw, 19px);
  font-weight: 500;
  line-height: 1.5;
  letter-spacing: 0.02em;
  color: var(--paper);
}

.ab-tl__text {
  margin: 0;
  font-size: clamp(14px, 1.4vw, 16px);
  line-height: 1.8;
  color: var(--silver);
  max-width: 34em;
}

/* ---------- 折线图 ---------- */
.ab-chart {
  margin-top: clamp(30px, 5vw, 52px);
  padding-top: clamp(20px, 3vw, 28px);
  border-top: 1px solid var(--line);
}

.ab-chart__cap {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--frost);
}

.ab-chart__svg {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  overflow: visible;
}

.ab-chart__axis {
  stroke: var(--line);
  stroke-width: 1;
}

.ab-chart__area {
  fill: url(#abChartFill);
}

.ab-chart__line {
  fill: none;
  stroke: var(--cyan);
  stroke-width: 1.5;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.ab-chart__node circle {
  fill: var(--ink);
  stroke: var(--cyan);
  stroke-width: 1.5;
  transition: r var(--t), fill var(--t);
}

.ab-chart__node:hover circle,
.ab-chart__node:focus-within circle {
  r: 7;
  fill: var(--cyan);
}

.ab-chart__node:focus {
  outline: none;
}

.ab-chart__tip {
  fill: var(--cyan);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
  opacity: 0;
  transition: opacity var(--t);
}

.ab-chart__node:hover .ab-chart__tip,
.ab-chart__node:focus-within .ab-chart__tip {
  opacity: 1;
}

.ab-chart__label {
  fill: var(--frost);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
}

/* ---------- 错位图文带 ---------- */
.ab-band {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(18px, 3vw, 32px);
  margin-bottom: clamp(24px, 4vw, 40px);
}

.ab-band__figure {
  margin-bottom: 0;
}

.ab-band__text .ab-sec__text:first-child {
  margin-top: 0;
}

/* ---------- 资料行 ---------- */
.ab-facts {
  border-top: 1px solid var(--line);
}

.ab-sec--paper .ab-facts {
  border-top-color: var(--ab-line-soft);
}

.ab-facts__row {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 6px 18px;
  padding: 13px 0;
  border-bottom: 1px solid var(--line);
  transition: border-color var(--t);
}

.ab-sec--paper .ab-facts__row {
  border-bottom-color: var(--ab-line-soft);
}

.ab-facts__row:hover {
  border-bottom-color: var(--cyan);
}

.ab-facts__k {
  font-size: clamp(14px, 1.4vw, 16px);
  line-height: 1.7;
  color: var(--silver);
}

.ab-sec--paper .ab-facts__k {
  color: var(--ab-ink-soft);
}

.ab-facts__v {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--moss);
}

.ab-sec--paper .ab-facts__v {
  color: var(--moss);
}

/* ---------- 双栏 ---------- */
.ab-cols {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(22px, 3.5vw, 44px);
}

.ab-cols__title {
  margin: 0 0 12px;
  font-family: var(--font-display);
  font-weight: 400;
  font-size: clamp(17px, 1.8vw, 21px);
  line-height: 1.5;
  letter-spacing: 0.03em;
  color: var(--ink);
  padding-bottom: 10px;
  border-bottom: 1px solid var(--ab-line-soft);
}

/* ---------- 后续方向 ---------- */
.ab-next {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  margin-top: clamp(18px, 3vw, 28px);
  background-color: var(--line);
  border: 1px solid var(--line);
  border-radius: 3px;
  overflow: hidden;
}

.ab-next__item {
  padding: clamp(18px, 2.6vw, 28px);
  background-color: var(--rock);
  transition: background-color var(--t);
}

.ab-next__item:hover {
  background-color: #1A2634;
}

.ab-next__no {
  display: inline-block;
  margin-bottom: 12px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  color: var(--clay);
}

.ab-next__title {
  margin: 0 0 10px;
  font-size: clamp(16px, 1.7vw, 19px);
  font-weight: 500;
  line-height: 1.5;
  letter-spacing: 0.02em;
  color: var(--paper);
}

.ab-next__text {
  margin: 0;
  font-size: clamp(14px, 1.4vw, 16px);
  line-height: 1.8;
  color: var(--silver);
}

/* ---------- 收尾引导 ---------- */
.ab-cta {
  padding-block: clamp(38px, 6vw, 72px);
  border-top: 1px solid var(--line);
  background-image: linear-gradient(180deg, rgba(185, 106, 75, 0.12), rgba(11, 18, 32, 0) 70%);
}

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

.ab-cta__title {
  margin: 0 0 12px;
  font-family: var(--font-display);
  font-weight: 300;
  font-size: clamp(22px, 2.8vw, 32px);
  line-height: 1.3;
  letter-spacing: 0.02em;
  color: var(--paper);
}

.ab-cta__text {
  margin: 0;
  font-size: clamp(14px, 1.5vw, 16px);
  line-height: 1.85;
  max-width: 42em;
  color: var(--silver);
}

.ab-cta__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-content: start;
}

/* ---------- 响应式 ---------- */
@media (min-width: 620px) {
  .ab-next {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 860px) {
  .ab-sec__grid {
    grid-template-columns: var(--ab-year) minmax(0, 1fr);
    gap: clamp(24px, 4vw, 56px);
  }

  .ab-sec__rail {
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
  }

  .ab-sec__body {
    border-left: 1px solid var(--line);
    padding-left: clamp(20px, 3vw, 40px);
  }

  .ab-sec--paper .ab-sec__body {
    border-left-color: var(--ab-line-soft);
  }

  .ab-band {
    grid-template-columns: minmax(0, 5fr) minmax(0, 6fr);
    align-items: start;
  }

  .ab-band__text {
    padding-top: clamp(26px, 4.5vw, 58px);
  }

  .ab-cols {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .ab-cta__inner {
    grid-template-columns: minmax(0, 7fr) minmax(0, 4fr);
    align-items: end;
  }

  .ab-cta__actions {
    justify-content: flex-end;
  }
}

@media (min-width: 960px) {
  .ab-hero__grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
    align-items: start;
  }
}

@media (min-width: 1200px) {
  .page-about {
    padding-right: var(--rail-w);
  }

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