.page-about {
  --about-rail-w: 232px;
  --about-flow-max: 760px;
  display: block;
  overflow-wrap: break-word;
}

/* ---------- 顶部状态条 ---------- */

.page-about .about-status {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px 18px;
  padding-block: 18px;
  border-bottom: 1px solid var(--grid);
  font-size: 13px;
  color: var(--ink-2);
}

.page-about .about-status__text {
  font-size: 13px;
  letter-spacing: 0.04em;
}

.page-about .about-status .breadcrumb {
  margin-left: auto;
}

/* ---------- 首屏 ---------- */

.page-about .about-hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 22px;
  padding-block: clamp(48px, 9vw, 104px) clamp(36px, 6vw, 68px);
}

.page-about .about-hero__head {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.page-about .about-hero__title {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 400;
  font-size: clamp(2.4rem, 7vw, 4.4rem);
  line-height: 1.02;
  letter-spacing: 0.01em;
  color: var(--ink);
}

.page-about .about-lede {
  margin: 0;
  max-width: 62ch;
  font-size: 16px;
  line-height: 1.85;
  color: var(--ink-2);
}

.page-about .about-facts {
  list-style: none;
  margin: 10px 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px 18px;
}

.page-about .about-fact {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding-top: 14px;
  border-top: 1px solid var(--grid);
}

.page-about .about-fact .metric-value {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: clamp(1.25rem, 3.4vw, 1.65rem);
  line-height: 1.1;
  color: var(--gold);
  text-shadow: 0 0 1px rgba(216, 180, 90, 0.85);
}

.page-about .about-fact .metric-label {
  font-size: 13px;
  line-height: 1.5;
  color: var(--ink-2);
}

/* ---------- 主体结构 ---------- */

.page-about .about-body {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 32px;
}

.page-about .about-flow {
  border-top: 1px solid var(--grid);
}

/* ---------- 右侧章节索引 ---------- */

.page-about .about-rail {
  order: -1;
  position: sticky;
  top: 68px;
  z-index: 4;
  padding: 12px 14px;
  border: 1px solid var(--grid);
  border-radius: var(--r-md);
  background: rgba(11, 17, 25, 0.96);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

.page-about .about-rail__label {
  margin: 0 0 10px;
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--ink-2);
}

.page-about .about-rail__list {
  display: flex;
  gap: 8px;
  margin: 0;
  padding: 0 0 4px;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: none;
}

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

.page-about .rail-node {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  flex: 0 0 auto;
  padding: 8px 14px;
  border: 1px solid var(--grid);
  border-radius: var(--r-pill);
  background: var(--panel);
  color: var(--ink-2);
  font-size: 12.5px;
  line-height: 1;
  text-decoration: none;
  white-space: nowrap;
  transition: border-color 240ms var(--ease), color 240ms var(--ease);
}

.page-about .rail-node__code {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 11px;
  letter-spacing: 0.08em;
  color: var(--gold);
}

.page-about .rail-node:hover,
.page-about .rail-node:focus-visible {
  border-color: var(--gold);
  color: var(--gold-hi);
  outline: none;
}

/* ---------- 章节 ---------- */

.page-about .chapter {
  padding-block: clamp(46px, 7vw, 86px);
}

.page-about .chapter + .chapter {
  border-top: 1px solid var(--grid);
}

.page-about .chapter-head {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.page-about .chapter-title {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 400;
  font-size: clamp(1.55rem, 4.6vw, 2.4rem);
  line-height: 1.18;
  letter-spacing: 0.01em;
  color: var(--ink);
  transition: color 240ms var(--ease);
}

.page-about .chapter:target .chapter-title {
  color: var(--gold-hi);
}

.page-about .chapter-body {
  max-width: 62ch;
  margin-top: 22px;
}

.page-about .chapter-body p {
  margin: 0 0 1.05em;
  font-size: 16px;
  line-height: 1.85;
  color: var(--ink);
}

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

.page-about .chapter-body a {
  color: var(--blue);
  text-decoration: none;
  border-bottom: 1px solid rgba(59, 199, 245, 0.34);
  transition: border-color 200ms var(--ease), color 200ms var(--ease);
}

.page-about .chapter-body a:hover,
.page-about .chapter-body a:focus-visible {
  color: var(--gold-hi);
  border-bottom-color: var(--gold);
}

/* ---------- 口径变化点小卡 ---------- */

.page-about .delta-card {
  max-width: 62ch;
  margin-top: 30px;
  padding: 18px 22px;
  border-left: 1px solid var(--gold);
  border-radius: 0 var(--r-sm) var(--r-sm) 0;
  background: linear-gradient(90deg, rgba(216, 180, 90, 0.09), rgba(216, 180, 90, 0) 78%);
}

.page-about .delta-card__label {
  margin: 0 0 8px;
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--gold);
}

.page-about .delta-card__text {
  margin: 0;
  font-size: 15px;
  line-height: 1.8;
  color: var(--ink-2);
}

/* ---------- 图片 ---------- */

.page-about .chapter-media {
  width: 100%;
  max-width: var(--about-flow-max);
  margin: 32px 0 0;
  border: 1px solid var(--grid);
  border-radius: var(--r-lg);
  overflow: hidden;
  background: var(--panel);
}

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

.page-about .about-figure--2x1 img {
  aspect-ratio: 2 / 1;
}

.page-about .about-figure--3x2 img {
  aspect-ratio: 3 / 2;
}

.page-about .about-figure--4x3 img {
  aspect-ratio: 4 / 3;
}

.page-about .about-figure .media-frame__caption {
  padding: 12px 16px;
  border-top: 1px solid var(--grid);
  font-size: 12.5px;
  line-height: 1.6;
  color: var(--ink-2);
}

/* ---------- 版本手风琴 ---------- */

.page-about .about-versions {
  margin-top: 30px;
  max-width: var(--about-flow-max);
}

.page-about .about-versions .accordion-trigger {
  gap: 14px;
}

.page-about .version-code {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 13px;
  letter-spacing: 0.06em;
  color: var(--gold);
  text-shadow: 0 0 1px rgba(216, 180, 90, 0.85);
}

.page-about .version-name {
  color: var(--ink);
}

.page-about .about-versions .accordion-body p {
  margin: 0;
  font-size: 15px;
  line-height: 1.8;
  color: var(--ink-2);
}

/* ---------- 结尾去向 ---------- */

.page-about .about-next {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 16px;
  padding-block: clamp(48px, 8vw, 92px);
  border-top: 1px solid var(--grid);
}

.page-about .about-next__links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-left: auto;
}

/* ---------- 桌面端 ---------- */

@media (min-width: 640px) {
  .page-about .about-facts {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

@media (min-width: 1024px) {
  .page-about .about-hero {
    grid-template-columns: minmax(0, 1.35fr) minmax(0, 1fr);
    grid-template-areas:
      "head facts"
      "lede facts";
    column-gap: clamp(40px, 6vw, 96px);
    row-gap: 26px;
    align-items: start;
  }

  .page-about .about-hero__head {
    grid-area: head;
  }

  .page-about .about-lede {
    grid-area: lede;
    max-width: 62ch;
  }

  .page-about .about-facts {
    grid-area: facts;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    margin-top: 6px;
  }

  .page-about .about-body {
    grid-template-columns: minmax(0, 1fr) var(--about-rail-w);
    column-gap: clamp(40px, 6vw, 96px);
    align-items: start;
  }

  .page-about .about-rail {
    order: 0;
    top: 112px;
    padding: 0 0 0 20px;
    border: none;
    border-radius: 0;
    background: none;
    backdrop-filter: none;
    -webkit-backdrop-filter: none;
  }

  .page-about .about-rail::before {
    content: "";
    position: absolute;
    left: 0;
    top: 10px;
    bottom: 10px;
    width: 1px;
    background: linear-gradient(180deg, var(--gold), var(--grid) 52%, rgba(34, 48, 63, 0) 100%);
  }

  .page-about .about-rail__list {
    flex-direction: column;
    gap: 0;
    padding: 0;
    overflow: visible;
  }

  .page-about .rail-node {
    display: block;
    position: relative;
    flex: 0 0 auto;
    padding: 9px 0;
    border: none;
    border-radius: 0;
    background: none;
    color: var(--ink-2);
    font-size: 13px;
    line-height: 1.5;
    white-space: normal;
    transition: color 220ms var(--ease);
  }

  .page-about .rail-node::before {
    content: "";
    position: absolute;
    left: -23.5px;
    top: 50%;
    width: 7px;
    height: 7px;
    margin-top: -3.5px;
    border-radius: 50%;
    background: var(--grid);
    transition: background 220ms var(--ease), box-shadow 220ms var(--ease);
  }

  .page-about .rail-node:hover,
  .page-about .rail-node:focus-visible {
    border: none;
    color: var(--gold-hi);
  }

  .page-about .rail-node:hover::before,
  .page-about .rail-node:focus-visible::before {
    background: var(--gold);
    box-shadow: 0 0 0 4px rgba(216, 180, 90, 0.16);
  }
}

@media (min-width: 1280px) {
  .page-about .about-flow {
    padding-right: 12px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .rail-node,
  .page-about .chapter-title,
  .page-about .chapter-body a,
  .page-about .delta-card {
    transition: none;
  }
}