.page-about {
  --ab-gap: clamp(28px, 4vw, 64px);
  --ab-ch-pad: clamp(28px, 4.5vw, 60px);
  background: var(--sand-100);
  color: var(--ink-900);
}

/* ---------- 首屏 ---------- */

.page-about .ab-hero {
  position: relative;
  overflow: hidden;
  background: var(--ink-900);
  color: var(--sand-100);
  padding-top: calc(var(--header-h) + clamp(44px, 8vw, 92px));
  padding-bottom: clamp(52px, 9vw, 108px);
}

.page-about .ab-hero-slab {
  position: absolute;
  display: block;
  pointer-events: none;
}

.page-about .ab-hero-slab--a {
  top: 14%;
  right: -14%;
  left: 44%;
  height: 66%;
  background: var(--ink-700);
  transform: skewY(-9deg);
}

.page-about .ab-hero-slab--b {
  right: 4%;
  bottom: -22%;
  width: 42%;
  height: 54%;
  background: var(--flame);
  opacity: 0.16;
  transform: skewY(-9deg);
}

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

.page-about .ab-crumb {
  margin-bottom: clamp(26px, 4vw, 46px);
}

.page-about .ab-crumb .breadcrumb-link,
.page-about .ab-crumb .breadcrumb-current {
  color: var(--ink-200);
}

.page-about .ab-hero-title {
  font-family: var(--font-display);
  font-size: clamp(1.875rem, 5vw, 3.5rem);
  line-height: 1.2;
  font-weight: 600;
  letter-spacing: 0;
  margin: 0 0 clamp(16px, 2.4vw, 26px);
  max-width: 18em;
  color: var(--paper);
}

.page-about .ab-hero-lede {
  max-width: 60ch;
  font-size: var(--fs-16);
  line-height: 1.95;
  color: var(--ink-200);
  margin: 0 0 clamp(30px, 4.8vw, 50px);
}

.page-about .ab-hero-facts {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 0;
  background: rgba(175, 194, 209, 0.26);
  border: 1px solid rgba(175, 194, 209, 0.26);
}

.page-about .ab-fact {
  background: var(--ink-900);
  padding: clamp(14px, 2.2vw, 22px) clamp(14px, 2vw, 22px);
}

.page-about .ab-fact dt {
  font-size: var(--fs-12);
  font-weight: 600;
  letter-spacing: 0.09em;
  color: var(--ink-400);
  margin-bottom: 10px;
}

.page-about .ab-fact-num {
  margin: 0;
  display: flex;
  align-items: baseline;
  gap: 6px;
}

.page-about .ab-fact .hp-num {
  font-family: var(--font-num);
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  line-height: 1;
  font-weight: 700;
}

.page-about .ab-fact .hp-unit {
  font-family: var(--font-body);
  font-size: var(--fs-14);
  font-weight: 400;
  color: var(--ink-200);
}

/* ---------- 主体网格 ---------- */

.page-about .ab-body {
  padding-top: clamp(34px, 5vw, 66px);
  padding-bottom: clamp(56px, 8vw, 104px);
}

.page-about .ab-grid {
  display: grid;
  gap: clamp(20px, 4vw, 40px);
}

/* ---------- 左侧年份刻度 ---------- */

.page-about .ab-rail {
  align-self: start;
}

.page-about .ab-rail-title {
  font-size: var(--fs-12);
  font-weight: 600;
  letter-spacing: 0.12em;
  color: var(--ink-400);
  margin: 0 0 14px;
}

.page-about .ab-scale {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(76px, 1fr));
  gap: 8px;
}

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

.page-about .ab-scale-link {
  display: flex;
  flex-direction: column;
  gap: 2px;
  padding: 8px 10px;
  text-decoration: none;
  background: rgba(255, 253, 248, 0.6);
  border: 1px solid rgba(175, 194, 209, 0.6);
  border-radius: var(--radius);
  transition: color 160ms var(--ease), background 160ms var(--ease), border-color 160ms var(--ease);
}

.page-about .ab-scale-link:hover,
.page-about .ab-scale-link:focus-visible {
  background: var(--paper);
  border-color: var(--flame);
}

.page-about .ab-scale-year {
  font-family: var(--font-num);
  font-size: var(--fs-16);
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--ink-900);
}

.page-about .ab-scale-note {
  font-size: var(--fs-12);
  color: var(--ink-400);
}

.page-about .ab-rail-note {
  margin-top: clamp(16px, 2.6vw, 24px);
  padding: clamp(14px, 2vw, 18px);
  font-size: var(--fs-12);
  line-height: 1.8;
  color: var(--ink-700);
  background: rgba(255, 253, 248, 0.66);
  border: 1px solid rgba(175, 194, 209, 0.6);
  border-radius: var(--radius);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
}

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

/* ---------- 右侧正文流 ---------- */

.page-about .ab-stream {
  min-width: 0;
  border: 1px solid var(--ink-200);
  background: var(--paper);
}

.page-about .ab-chapter {
  padding: var(--ab-ch-pad);
  border-bottom: 1px solid rgba(175, 194, 209, 0.55);
}

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

.page-about .ab-chapter:nth-child(even) {
  background: var(--sand-300);
}

.page-about .ab-ch-head {
  display: flex;
  align-items: baseline;
  gap: clamp(12px, 2vw, 20px);
  margin-bottom: clamp(14px, 2.4vw, 22px);
}

.page-about .ab-ch-no {
  font-family: var(--font-num);
  font-size: var(--fs-26);
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1;
  color: var(--flame);
  margin: 0;
  flex: none;
}

.page-about .ab-ch-title {
  font-family: var(--font-display);
  font-size: clamp(1.3125rem, 2.8vw, 1.875rem);
  line-height: 1.38;
  font-weight: 600;
  margin: 0;
  color: var(--ink-900);
}

.page-about .ab-ch-lead {
  font-family: var(--font-display);
  font-size: clamp(1.0625rem, 1.9vw, 1.25rem);
  line-height: 1.8;
  font-weight: 500;
  color: var(--ink-700);
  margin: 0 0 clamp(14px, 2.2vw, 22px);
  max-width: 48ch;
}

.page-about .ab-chapter p {
  font-size: var(--fs-16);
  line-height: 1.9;
  margin: 0 0 1em;
  max-width: 62ch;
}

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

.page-about .ab-note {
  margin: clamp(18px, 2.8vw, 28px) 0 0;
  padding: clamp(15px, 2.3vw, 22px) clamp(16px, 2.4vw, 24px);
  max-width: 60ch;
  background: rgba(255, 253, 248, 0.74);
  border-left: 3px solid var(--flame);
  -webkit-backdrop-filter: blur(6px);
  backdrop-filter: blur(6px);
}

.page-about .ab-note-tag {
  font-size: var(--fs-12);
  font-weight: 600;
  letter-spacing: 0.09em;
  color: var(--flame-deep);
  margin: 0 0 6px;
}

.page-about .ab-note p {
  margin: 0;
  font-size: var(--fs-14);
  line-height: 1.8;
  color: var(--ink-700);
}

/* ---------- 档位并置 ---------- */

.page-about .ab-tiers {
  list-style: none;
  margin: clamp(20px, 3vw, 32px) 0 clamp(20px, 3vw, 30px);
  padding: 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(158px, 1fr));
  gap: 1px;
  background: var(--ink-200);
  border: 1px solid var(--ink-200);
}

.page-about .ab-tier {
  background: var(--paper);
  padding: clamp(15px, 2.3vw, 22px);
}

.page-about .ab-tier-idx {
  display: block;
  font-family: var(--font-num);
  font-size: var(--fs-20);
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--flame);
  margin-bottom: 8px;
}

.page-about .ab-tier-name {
  font-family: var(--font-display);
  font-size: var(--fs-16);
  font-weight: 600;
  margin: 0 0 8px;
  color: var(--ink-900);
}

.page-about .ab-tier-desc {
  font-size: var(--fs-14);
  line-height: 1.78;
  color: var(--ink-700);
  margin: 0;
  max-width: none;
}

/* ---------- 图片 ---------- */

.page-about .ab-figure {
  margin: clamp(22px, 3.4vw, 34px) 0 clamp(20px, 3vw, 30px);
  padding: 0;
  max-width: 100%;
}

.page-about .ab-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  border-radius: var(--radius);
  background: var(--sand-300);
}

.page-about .ab-figure--wide img {
  aspect-ratio: 3 / 2;
}

.page-about .ab-figure--mid img {
  aspect-ratio: 10 / 7;
}

.page-about .ab-figure--tall img {
  aspect-ratio: 3 / 4;
  max-width: 360px;
}

.page-about .media-cap {
  margin-top: 10px;
  font-size: var(--fs-12);
  line-height: 1.7;
  color: var(--ink-400);
  max-width: 52ch;
}

/* ---------- 分拨点 ---------- */

.page-about .ab-hubs {
  list-style: none;
  margin: clamp(20px, 3vw, 32px) 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(148px, 1fr));
  gap: clamp(10px, 1.6vw, 16px);
}

.page-about .ab-hub {
  padding: clamp(15px, 2.3vw, 22px);
  background: var(--ink-900);
  color: var(--sand-100);
  border-radius: var(--radius);
  transition: transform 200ms var(--ease), box-shadow 200ms var(--ease);
}

.page-about .ab-hub:hover,
.page-about .ab-hub:focus-within {
  transform: translateY(-3px);
  box-shadow: var(--shadow-soft);
}

.page-about .ab-hub-name {
  font-family: var(--font-display);
  font-size: var(--fs-20);
  font-weight: 600;
  margin: 0 0 8px;
  color: var(--paper);
}

.page-about .ab-hub p {
  font-size: var(--fs-14);
  line-height: 1.75;
  color: var(--ink-200);
  margin: 0;
  max-width: none;
}

.page-about .ab-hub-more {
  display: block;
  margin-top: 12px;
  padding-top: 10px;
  border-top: 1px solid rgba(175, 194, 209, 0.28);
  font-size: var(--fs-12);
  line-height: 1.7;
  color: var(--ink-400);
  transition: color 200ms var(--ease);
}

.page-about .ab-hub:hover .ab-hub-more,
.page-about .ab-hub:focus-within .ab-hub-more {
  color: var(--sand-300);
}

/* ---------- 时间线 ---------- */

.page-about .ab-timeline {
  list-style: none;
  margin: clamp(20px, 3vw, 32px) 0 0;
  padding: 0;
  border-top: 1px solid var(--ink-200);
}

.page-about .ab-tl-item {
  display: grid;
  gap: 4px;
  padding: clamp(14px, 2.2vw, 20px) 0;
  border-bottom: 1px solid var(--ink-200);
  scroll-margin-top: calc(var(--header-h) + 28px);
}

.page-about .ab-tl-year {
  font-family: var(--font-num);
  font-size: clamp(1.5rem, 3.4vw, 2.25rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1;
  color: var(--flame);
}

.page-about .ab-tl-title {
  font-family: var(--font-display);
  font-size: var(--fs-16);
  font-weight: 600;
  margin: 0 0 6px;
  color: var(--ink-900);
}

.page-about .ab-tl-text {
  font-size: var(--fs-14);
  line-height: 1.82;
  color: var(--ink-700);
  margin: 0;
  max-width: 58ch;
}

/* ---------- 延伸入口 ---------- */

.page-about .ab-links {
  margin-top: clamp(22px, 3.2vw, 32px);
  padding-top: clamp(18px, 2.6vw, 26px);
  border-top: 1px solid var(--ink-200);
  display: grid;
  gap: 2px;
}

.page-about .ab-link {
  display: block;
  padding: 11px 0 11px 20px;
  position: relative;
  font-size: var(--fs-16);
  line-height: 1.7;
  color: var(--ink-700);
  text-decoration: none;
  border-bottom: 1px solid rgba(175, 194, 209, 0.6);
  transition: color 180ms var(--ease), padding-left 180ms var(--ease);
}

.page-about .ab-link::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: 10px;
  height: 2px;
  margin-top: -1px;
  background: var(--ink-200);
  transition: background 180ms var(--ease), width 180ms var(--ease);
}

.page-about .ab-link:hover,
.page-about .ab-link:focus-visible {
  color: var(--flame-deep);
  padding-left: 26px;
}

.page-about .ab-link:hover::before,
.page-about .ab-link:focus-visible::before {
  background: var(--flame);
  width: 16px;
}

/* ---------- 桌面布局 ---------- */

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

@media (min-width: 900px) {
  .page-about .ab-grid {
    grid-template-columns: clamp(170px, 17vw, 214px) minmax(0, 1fr);
    gap: var(--ab-gap);
    align-items: start;
  }

  .page-about .ab-rail-inner {
    position: sticky;
    top: calc(var(--header-h) + 24px);
  }

  .page-about .ab-scale {
    grid-template-columns: 1fr;
    gap: 0;
    position: relative;
    padding-left: 22px;
  }

  .page-about .ab-scale::before {
    content: "";
    position: absolute;
    left: 5px;
    top: 10px;
    bottom: 10px;
    width: 1px;
    background: var(--ink-200);
  }

  .page-about .ab-scale-link {
    flex-direction: row;
    align-items: baseline;
    gap: 10px;
    padding: 9px 0;
    position: relative;
    background: none;
    border: 0;
    border-radius: 0;
  }

  .page-about .ab-scale-link::before {
    content: "";
    position: absolute;
    left: -22px;
    top: 50%;
    width: 11px;
    height: 11px;
    margin-top: -5.5px;
    border-radius: 50%;
    background: var(--sand-100);
    border: 2px solid var(--ink-200);
    transition: background 160ms var(--ease), border-color 160ms var(--ease);
  }

  .page-about .ab-scale-link:hover,
  .page-about .ab-scale-link:focus-visible {
    background: none;
    border-color: transparent;
  }

  .page-about .ab-scale-link:hover::before,
  .page-about .ab-scale-link:focus-visible::before {
    background: var(--flame);
    border-color: var(--flame);
  }

  .page-about .ab-tl-item {
    grid-template-columns: 96px minmax(0, 1fr);
    gap: clamp(16px, 3vw, 34px);
    align-items: baseline;
  }
}

@media (min-width: 1120px) {
  .page-about .ab-figure--tall {
    margin-left: clamp(0px, 3vw, 40px);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .ab-hub,
  .page-about .ab-scale-link,
  .page-about .ab-scale-link::before,
  .page-about .ab-link,
  .page-about .ab-link::before,
  .page-about .ab-hub-more {
    transition: none;
  }

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