.page-about {
  --ab-gap: 32px;
  position: relative;
  background: var(--bg);
  color: var(--text);
  padding-bottom: 88px;
}

.page-about .ab-hero {
  padding-top: 24px;
}

.page-about .ab-hero__frame {
  position: relative;
  padding: clamp(26px, 4vw, 52px);
  background:
    radial-gradient(120% 140% at 100% 0%, rgba(109, 59, 200, 0.16), transparent 62%),
    var(--bg);
}

.page-about .ab-hero h1 {
  margin: 18px 0 0;
  font-size: clamp(30px, 5.4vw, 56px);
  line-height: 1.1;
  letter-spacing: -0.02em;
  font-weight: 800;
  max-width: 15em;
}

.page-about .ab-hero .lead {
  margin: 22px 0 0;
  max-width: 40em;
  color: var(--muted);
}

.page-about .ab-hero__meta {
  margin-top: 30px;
  padding-top: 18px;
  border-top: 1px solid var(--line-soft);
  display: flex;
  flex-wrap: wrap;
  gap: 10px 30px;
}

.page-about .ab-hero__meta span {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--muted);
}

.page-about .ab-hero__meta b {
  color: var(--brand-a);
  font-weight: 600;
}

/* ---------- 主体双栏 ---------- */

.page-about .ab-body {
  display: grid;
  gap: var(--ab-gap);
  padding-top: 56px;
}

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

/* ---------- 左侧章节索引 ---------- */

.page-about .ab-rail {
  display: none;
}

.page-about .ab-rail__title {
  margin: 0 0 14px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--muted);
}

.page-about .ab-rail__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 2px;
}

.page-about .ab-rail__node {
  position: relative;
  display: grid;
  grid-template-columns: 54px minmax(0, 1fr);
  gap: 10px;
  align-items: baseline;
  padding: 9px 0;
  text-decoration: none;
  color: var(--muted);
  transition: color 0.2s var(--ease);
}

.page-about .ab-rail__node::before {
  content: "";
  position: absolute;
  left: -9px;
  top: 50%;
  width: 7px;
  height: 7px;
  margin-top: -3.5px;
  border-radius: 50%;
  background: var(--panel);
  border: 1px solid var(--line);
  transition: background 0.2s var(--ease), border-color 0.2s var(--ease), box-shadow 0.2s var(--ease);
}

.page-about .ab-rail__node:hover,
.page-about .ab-rail__node:focus-visible {
  color: var(--text);
}

.page-about .ab-rail__node:hover::before,
.page-about .ab-rail__node:focus-visible::before {
  background: var(--brand-a);
  border-color: var(--brand-a-hi);
}

.page-about .ab-rail__yr {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--brand-a);
}

.page-about .ab-rail__lb {
  font-size: 13px;
  letter-spacing: 0.02em;
}

.page-about:has(#start:target) .ab-rail__node[href="#start"],
.page-about:has(#review:target) .ab-rail__node[href="#review"],
.page-about:has(#team:target) .ab-rail__node[href="#team"],
.page-about:has(#versions:target) .ab-rail__node[href="#versions"],
.page-about:has(#sources:target) .ab-rail__node[href="#sources"],
.page-about:has(#standards:target) .ab-rail__node[href="#standards"] {
  color: var(--text);
}

.page-about:has(#start:target) .ab-rail__node[href="#start"]::before,
.page-about:has(#review:target) .ab-rail__node[href="#review"]::before,
.page-about:has(#team:target) .ab-rail__node[href="#team"]::before,
.page-about:has(#versions:target) .ab-rail__node[href="#versions"]::before,
.page-about:has(#sources:target) .ab-rail__node[href="#sources"]::before,
.page-about:has(#standards:target) .ab-rail__node[href="#standards"]::before {
  background: var(--brand-a);
  border-color: var(--brand-a-hi);
  box-shadow: 0 0 0 3px var(--brand-a-tint);
}

/* ---------- 章节通用 ---------- */

.page-about .ab-sec {
  padding: 68px 0 0;
  scroll-margin-top: calc(var(--header-h) + 24px);
}

.page-about .ab-main > .ab-sec:first-child {
  padding-top: 0;
}

.page-about .ab-sec > p {
  margin-top: 16px;
  max-width: 38em;
  color: var(--muted);
}

.page-about .ab-sec .lead {
  color: var(--muted);
}

.page-about .ab-pull {
  margin: 26px 0 26px;
  padding: 6px 0 6px 22px;
  border-left: 3px solid var(--brand-a);
  font-size: clamp(19px, 2.6vw, 25px);
  line-height: 1.5;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--text);
  max-width: 22em;
}

.page-about .ab-note {
  margin-top: 24px;
  padding: 16px 18px;
  border: 1px solid var(--line-soft);
  border-left: 3px solid var(--brand-c);
  border-radius: var(--radius);
  background: var(--panel);
  font-size: 15px;
  line-height: 1.75;
  color: var(--muted);
  max-width: 42em;
}

/* ---------- 数据小卡 ---------- */

.page-about .ab-stats {
  margin-top: 30px;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  background: var(--line-faint);
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  overflow: hidden;
}

.page-about .ab-stat {
  background: var(--panel);
  padding: 18px 16px 20px;
}

.page-about .ab-stat__n {
  margin: 0;
  font-family: var(--mono);
  font-size: clamp(20px, 3.4vw, 26px);
  font-weight: 600;
  line-height: 1.1;
  letter-spacing: -0.01em;
  color: var(--brand-a);
}

.page-about .ab-stat__l {
  margin: 8px 0 0;
  font-size: 13px;
  line-height: 1.6;
  color: var(--muted);
}

/* ---------- 复核图与流程 ---------- */

.page-about .ab-fig {
  margin: 26px 0 0;
}

.page-about .ab-fig img {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  background: var(--panel);
  filter: saturate(0.7) contrast(1.05);
}

.page-about .ab-fig .media__cap {
  margin-top: 10px;
}

.page-about .ab-scroll {
  margin-top: 22px;
  overflow-x: auto;
  padding-bottom: 4px;
}

.page-about .ab-flow {
  display: block;
  width: 100%;
  min-width: 540px;
  height: auto;
}

.page-about .ab-flow__box {
  fill: var(--panel);
  stroke: var(--line);
  stroke-width: 1;
}

.page-about .ab-flow__num {
  font-family: var(--mono);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.12em;
  fill: var(--brand-a);
}

.page-about .ab-flow__ttl {
  font-family: var(--sans);
  font-size: 21px;
  font-weight: 700;
  fill: var(--text);
}

.page-about .ab-flow__sub {
  font-family: var(--mono);
  font-size: 12.5px;
  letter-spacing: 0.04em;
  fill: var(--muted);
}

.page-about .ab-flow__link {
  stroke: var(--line);
  stroke-width: 1;
}

.page-about .ab-flow__arrow {
  fill: var(--line);
}

/* ---------- 折叠延伸阅读 ---------- */

.page-about .ab-more {
  margin-top: 26px;
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  background: var(--panel);
}

.page-about .ab-more summary {
  cursor: pointer;
  padding: 15px 18px;
  font-size: 15px;
  font-weight: 600;
  color: var(--text);
  list-style: none;
}

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

.page-about .ab-more summary::before {
  content: "+";
  display: inline-block;
  width: 1.4em;
  font-family: var(--mono);
  color: var(--brand-a);
}

.page-about .ab-more[open] summary::before {
  content: "–";
}

.page-about .ab-more__body {
  padding: 0 18px 18px;
  border-top: 1px solid var(--line-faint);
}

.page-about .ab-more__body p {
  margin: 14px 0 0;
  font-size: 15px;
  line-height: 1.75;
  color: var(--muted);
  max-width: 40em;
}

/* ---------- 团队 ---------- */

.page-about .ab-team {
  position: relative;
  margin-top: 28px;
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--panel);
}

.page-about .ab-team__bg {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  opacity: 0.22;
  filter: saturate(0.45) contrast(1.05);
}

.page-about .ab-team::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, rgba(6, 7, 10, 0.62) 0%, rgba(6, 7, 10, 0.94) 76%);
}

.page-about .ab-team__body {
  position: relative;
  z-index: 1;
  padding: 26px 20px 28px;
}

.page-about .ab-team__body .lead {
  margin: 0;
  max-width: 40em;
}

.page-about .ab-team__grid {
  margin-top: 24px;
  display: grid;
  gap: 18px;
}

.page-about .ab-role {
  border-top: 1px solid var(--line);
  padding-top: 14px;
}

.page-about .ab-role__name {
  margin: 0;
  font-size: 16px;
  font-weight: 700;
  color: var(--text);
  letter-spacing: 0.01em;
}

.page-about .ab-role__desc {
  margin: 7px 0 0;
  font-size: 14px;
  line-height: 1.72;
  color: var(--muted);
}

/* ---------- 版本 ---------- */

.page-about .ab-ver {
  margin-top: 28px;
  display: grid;
  gap: 30px;
}

.page-about .ab-ver__text > p {
  margin: 0;
  max-width: 34em;
  color: var(--muted);
}

.page-about .ab-vlist {
  list-style: none;
  margin: 26px 0 0;
  padding: 0;
  display: grid;
  gap: 22px;
}

.page-about .ab-vlist__item {
  position: relative;
  padding-left: 18px;
  border-left: 1px solid var(--line);
}

.page-about .ab-vlist__tag {
  display: inline-block;
  font-family: var(--mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.14em;
  color: var(--brand-b-hi);
  border: 1px solid var(--brand-b-tint);
  background: var(--brand-b-tint);
  border-radius: var(--radius);
  padding: 3px 8px;
}

.page-about .ab-vlist__item p {
  margin: 10px 0 0;
  font-size: 15px;
  line-height: 1.75;
  color: var(--muted);
  max-width: 34em;
}

.page-about .ab-ver__fig {
  margin: 0;
}

.page-about .ab-ver__img {
  display: block;
  width: 100%;
  max-width: 260px;
  height: auto;
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  background: var(--panel);
  filter: saturate(0.7);
}

.page-about .ab-ver__fig .media__cap {
  margin-top: 10px;
}

/* ---------- 数据来源双段 ---------- */

.page-about .ab-two {
  margin-top: 18px;
  display: grid;
  gap: 18px;
}

.page-about .ab-two p {
  margin: 0;
  font-size: 16px;
  line-height: 1.78;
  color: var(--muted);
  max-width: 34em;
}

/* ---------- 三条标准 ---------- */

.page-about .ab-std {
  list-style: none;
  margin: 28px 0 0;
  padding: 0;
  display: grid;
  gap: 1px;
  background: var(--line-faint);
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  overflow: hidden;
}

.page-about .ab-std__item {
  background: var(--panel);
  padding: 22px 18px 24px;
}

.page-about .ab-std__item:nth-child(2) {
  background: var(--panel-2);
}

.page-about .ab-std__n {
  margin: 0;
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--brand-a);
}

.page-about .ab-std__t {
  margin: 10px 0 0;
  font-size: 19px;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--text);
}

.page-about .ab-std__d {
  margin: 10px 0 0;
  font-size: 15px;
  line-height: 1.75;
  color: var(--muted);
}

/* ---------- 结尾引导 ---------- */

.page-about .ab-cta {
  margin-top: 32px;
  padding: 26px 20px;
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  background:
    linear-gradient(120deg, rgba(34, 227, 211, 0.10), transparent 58%),
    var(--panel);
}

.page-about .ab-cta__t {
  margin: 0;
  font-size: 16px;
  font-weight: 600;
  color: var(--text);
}

.page-about .ab-cta__row {
  margin-top: 16px;
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.page-about .ab-footline {
  margin-top: 26px;
  font-size: 14px;
  line-height: 1.8;
  color: var(--muted);
  max-width: 42em;
}

.page-about .ab-footline a {
  color: var(--brand-a);
  text-decoration: none;
  border-bottom: 1px solid var(--brand-a-tint);
}

.page-about .ab-footline a:hover {
  color: var(--brand-a-hi);
  border-bottom-color: var(--brand-a-hi);
}

/* ---------- 响应式 ---------- */

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

  .page-about .ab-team__grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 20px 28px;
  }

  .page-about .ab-team__body {
    padding: 34px 30px 36px;
  }

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

  .page-about .ab-two {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 26px;
  }
}

@media (min-width: 860px) {
  .page-about .ab-ver {
    grid-template-columns: minmax(0, 1fr) 260px;
    gap: 48px;
    align-items: start;
  }

  .page-about .ab-ver__fig {
    position: sticky;
    top: calc(var(--header-h) + 32px);
  }

  .page-about .ab-cta {
    padding: 30px 28px;
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 18px;
  }

  .page-about .ab-cta__row {
    margin-top: 0;
  }
}

@media (min-width: 1000px) {
  .page-about .ab-body {
    grid-template-columns: minmax(200px, 232px) minmax(0, 1fr);
    gap: 56px;
    align-items: start;
  }

  .page-about .ab-rail {
    display: block;
    position: sticky;
    top: calc(var(--header-h) + 32px);
    align-self: start;
    padding: 22px 0 22px 18px;
    border-left: 1px solid var(--line);
    background: linear-gradient(180deg, var(--brand-b-tint), transparent 72%);
  }

  .page-about .ab-sec {
    padding-top: 76px;
  }
}

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