.page-about {
  --about-rail: 208px;
  --about-gap: 72px;
  padding-bottom: 96px;
}

/* ---------- 面包屑 ---------- */
.page-about .about-crumb {
  padding-top: 28px;
}

.page-about .about-crumb .breadcrumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  margin: 0;
  padding: 0;
  list-style: none;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--text-dim);
}

.page-about .about-crumb .breadcrumb__link {
  color: var(--text-dim);
  text-decoration: none;
  transition: color 180ms var(--ease);
}

.page-about .about-crumb .breadcrumb__link:hover {
  color: var(--green);
}

.page-about .about-crumb .breadcrumb__sep {
  color: var(--text-faint);
}

/* ---------- 首屏声明 ---------- */
.page-about .about-hero {
  padding: 56px 0 0;
}

.page-about .about-hero__eyebrow {
  margin: 0 0 20px;
  color: var(--text-dim);
}

.page-about .about-hero__title {
  margin: 0 0 26px;
  max-width: 15em;
  color: var(--text);
}

.page-about .about-hero__lead {
  margin: 0;
  max-width: 62ch;
  color: var(--text-mid);
  font-size: 17px;
  line-height: 1.85;
}

.page-about .about-hero__facts {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0;
  margin: 44px 0 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line);
}

.page-about .about-hero__facts li {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 16px 12px 16px 18px;
  border-left: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.page-about .about-hero__k {
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--text-dim);
}

.page-about .about-hero__v {
  font-size: 17px;
  letter-spacing: 0.04em;
  color: var(--text);
}

/* ---------- 主体两栏 ---------- */
.page-about .about-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
  margin-top: 16px;
}

.page-about .about-rail {
  padding: 30px 0 14px;
}

.page-about .about-rail__label {
  margin: 0 0 14px;
  font-size: 11px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--text-faint);
}

.page-about .about-rail__list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 2px 16px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .about-rail__link {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 9px 0;
  color: var(--text-dim);
  text-decoration: none;
  font-size: 13px;
  line-height: 1.5;
  transition: color 180ms var(--ease);
}

.page-about .about-rail__num {
  font-size: 11px;
  letter-spacing: 0.08em;
  color: var(--text-faint);
  transition: color 180ms var(--ease);
}

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

.page-about .about-rail__link:hover .about-rail__num,
.page-about .about-rail__link:focus-visible .about-rail__num {
  color: var(--orange);
}

.page-about .about-doc {
  min-width: 0;
}

.page-about .panel[id] {
  scroll-margin-top: 96px;
}

/* ---------- 章节内的通用块 ---------- */
.page-about .about-media {
  margin: 34px 0 0;
}

.page-about .about-media .media__caption {
  margin-top: 12px;
  font-size: 13px;
  line-height: 1.7;
  color: var(--text-dim);
}

.page-about .about-anchor {
  display: grid;
  grid-template-columns: 1fr;
  gap: 6px;
  margin: 30px 0 0;
  padding: 18px 20px;
  background: var(--ink-100);
  border: 1px solid var(--line);
  border-left: 2px solid var(--green);
  border-radius: var(--r);
}

.page-about .about-anchor--orange {
  border-left-color: var(--orange);
}

.page-about .about-anchor__k {
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--text-dim);
}

.page-about .about-anchor__v {
  font-size: 22px;
  letter-spacing: 0.02em;
  color: var(--text);
}

.page-about .about-anchor__d {
  font-size: 13px;
  line-height: 1.7;
  color: var(--text-dim);
}

/* ---------- 术语定义表 ---------- */
.page-about .about-defs {
  margin: 32px 0 0;
  padding: 0;
  border-top: 1px solid var(--line);
}

.page-about .about-defs > div {
  display: grid;
  grid-template-columns: 1fr;
  gap: 6px;
  padding: 16px 0;
  border-bottom: 1px solid var(--line);
  transition: background 200ms var(--ease);
}

.page-about .about-defs dt {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.04em;
  color: var(--text-dim);
}

.page-about .about-defs dd {
  margin: 0;
  font-size: 15px;
  line-height: 1.8;
  color: var(--text-mid);
}

/* ---------- 折叠条款 ---------- */
.page-about .about-fold {
  margin: 12px 0 0;
  background: var(--ink-100);
  border: 1px solid var(--line);
  border-radius: var(--r);
  transition: border-color 200ms var(--ease);
}

.page-about .about-fold[open] {
  border-color: var(--line-hi);
}

.page-about .about-fold__sum {
  display: flex;
  align-items: baseline;
  gap: 14px;
  padding: 16px 18px;
  list-style: none;
  cursor: pointer;
  font-size: 15px;
  color: var(--text);
  transition: background 180ms var(--ease);
}

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

.page-about .about-fold__sum::after {
  content: "+";
  margin-left: auto;
  font-family: var(--font-mono);
  color: var(--text-dim);
  transition: color 180ms var(--ease);
}

.page-about .about-fold[open] .about-fold__sum::after {
  content: "–";
  color: var(--orange);
}

.page-about .about-fold__sum:hover {
  background: var(--ink-200);
}

.page-about .about-fold__sum:focus-visible {
  outline: 2px solid var(--green);
  outline-offset: 2px;
}

.page-about .about-fold__step {
  font-size: 12px;
  letter-spacing: 0.1em;
  color: var(--orange);
}

.page-about .about-fold__body {
  padding: 0 18px 18px;
  font-size: 15px;
  line-height: 1.85;
  color: var(--text-mid);
}

.page-about .about-fold__body p {
  margin: 0;
}

/* ---------- 角色列表 ---------- */
.page-about .about-roles {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
  margin: 30px 0 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line);
}

.page-about .about-roles__item {
  display: grid;
  grid-template-columns: 1fr;
  gap: 8px;
  padding: 18px 0;
  border-bottom: 1px solid var(--line);
}

.page-about .about-roles__name {
  font-size: 13px;
  letter-spacing: 0.08em;
  color: var(--green);
}

.page-about .about-roles__text {
  margin: 0;
  font-size: 15px;
  line-height: 1.85;
  color: var(--text-mid);
}

/* ---------- 中屏 ---------- */
@media (min-width: 640px) {
  .page-about .about-defs > div {
    grid-template-columns: 170px minmax(0, 1fr);
    gap: 0 24px;
    align-items: baseline;
  }

  .page-about .about-roles__item {
    grid-template-columns: 170px minmax(0, 1fr);
    gap: 0 24px;
    align-items: baseline;
  }

  .page-about .about-roles__text {
    margin: 0;
  }
}

/* ---------- 桌面 ---------- */
@media (min-width: 900px) {
  .page-about .about-hero {
    padding: 72px 0 0;
  }

  .page-about .about-hero__facts {
    grid-template-columns: repeat(4, minmax(0, 1fr));
    margin-top: 56px;
  }

  .page-about .about-layout {
    grid-template-columns: var(--about-rail) minmax(0, 1fr);
    gap: 0 var(--about-gap);
    margin-top: 48px;
  }

  .page-about .about-rail {
    padding: 72px 0;
  }

  .page-about .about-rail__sticky {
    position: sticky;
    top: 96px;
  }

  .page-about .about-rail__list {
    display: flex;
    flex-direction: column;
    gap: 0;
    border-left: 1px solid var(--line);
  }

  .page-about .about-rail__link {
    position: relative;
    display: block;
    padding: 11px 0 11px 18px;
  }

  .page-about .about-rail__num {
    margin-right: 10px;
  }

  .page-about .about-rail__link::before {
    content: "";
    position: absolute;
    left: -4px;
    top: 15px;
    width: 7px;
    height: 7px;
    border-radius: 50%;
    background: var(--ink-000);
    border: 1px solid var(--line-hi);
    transition: background 200ms var(--ease), border-color 200ms var(--ease);
  }

  .page-about .about-rail__link:hover::before,
  .page-about .about-rail__link:focus-visible::before {
    background: var(--green);
    border-color: var(--green);
  }

  .page-about .about-doc > .panel:first-child {
    border-top: 1px solid var(--line);
  }

  .page-about .about-anchor {
    padding: 22px 26px;
    gap: 8px;
  }

  .page-about .about-roles {
    margin-top: 36px;
  }
}

/* ---------- 动效降级 ---------- */
@media (prefers-reduced-motion: reduce) {
  .page-about * {
    transition-duration: 0.01ms !important;
  }
}
</final>