.page-about {
  --about-hair: rgba(20, 24, 28, .22);
  --about-panel-line: rgba(239, 234, 221, .28);
}

/* 页首 */
.page-about .about-hero {
  padding-block: 26px 42px;
  border-bottom: var(--border-1);
  background-image:
    radial-gradient(circle at 90% 2%, rgba(31, 107, 59, .16), transparent 58%),
    radial-gradient(circle at 3% 96%, rgba(12, 34, 51, .1), transparent 54%);
  background-repeat: no-repeat;
}

.page-about .about-hero__inner {
  display: grid;
  gap: 14px;
}

.page-about .about-hero__title {
  margin: 0;
  max-width: 24ch;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(30px, 8vw, 76px);
  line-height: 1.06;
  letter-spacing: -.02em;
  color: var(--ink);
}

.page-about .about-hero__lead {
  margin: 0;
  max-width: 48ch;
  font-size: 17px;
  line-height: 1.75;
  color: var(--ink);
}

.page-about .about-hero__meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 12px;
  margin: 0;
  font-size: 13px;
  line-height: 1.6;
  color: var(--noise);
}

.page-about .about-hero__media {
  margin: 12px 0 0;
}

/* 通用分节 */
.page-about .about-section {
  padding-block: 46px 52px;
}

.page-about .about-section + .about-section {
  border-top: 2px solid var(--ash);
}

.page-about .about-section__inner {
  display: grid;
  gap: 22px;
}

.page-about .about-note {
  margin: 0;
  max-width: 56ch;
  padding-left: 16px;
  border-left: 3px solid var(--ash);
  font-size: 14px;
  line-height: 1.75;
  color: var(--noise);
}

/* 双轨卡片补充 */
.page-about .about-track__title {
  margin: 6px 0 12px;
  font-family: var(--font-display);
  font-size: 21px;
  font-weight: 800;
  letter-spacing: -.01em;
  line-height: 1.3;
}

.page-about .track__list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 10px;
  font-size: 15px;
  line-height: 1.7;
}

.page-about .track__list li {
  position: relative;
  padding-left: 16px;
}

.page-about .track__list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: .62em;
  width: 7px;
  height: 7px;
  border: 2px solid var(--ink);
  background: var(--ash);
}

.page-about .track__side--reg .track__list li::before {
  background: var(--reg);
}

.page-about .track__side--app .track__list li::before {
  background: var(--app);
}

/* 口径图例 */
.page-about .rule-legend {
  display: grid;
  gap: 14px;
}

.page-about .rule-legend__item {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 8px 12px;
  align-items: center;
  padding: 16px 18px;
  border: var(--border-1);
  border-left-width: 9px;
  background: var(--paper);
  transition: box-shadow 200ms var(--ease), transform 200ms var(--ease);
}

.page-about .rule-legend__item--reg {
  border-left-color: var(--reg);
}

.page-about .rule-legend__item--app {
  border-left-color: var(--app);
}

.page-about .rule-legend__item:hover,
.page-about .rule-legend__item:focus-visible {
  outline: none;
  transform: translate(-2px, -2px);
  box-shadow: var(--shadow-2);
}

.page-about .rule-legend__name {
  font-family: var(--font-mono);
  font-size: 15px;
  font-weight: 700;
  letter-spacing: .02em;
  color: var(--ink);
}

.page-about .rule-legend__desc {
  grid-column: 1 / -1;
  margin: 0;
  max-width: 62ch;
  font-size: 13px;
  line-height: 1.7;
  color: var(--noise);
  opacity: .78;
  transition: opacity 200ms var(--ease), color 200ms var(--ease);
}

.page-about .rule-legend__item:hover .rule-legend__desc,
.page-about .rule-legend__item:focus-visible .rule-legend__desc {
  opacity: 1;
  color: var(--ink);
}

/* 图文分栏 */
.page-about .about-split {
  display: grid;
  gap: 24px;
}

.page-about .about-split__body {
  display: grid;
  gap: 18px;
  align-content: start;
}

.page-about .about-split__body > p {
  margin: 0;
  max-width: 52ch;
  font-size: 15px;
  line-height: 1.75;
  color: var(--ink);
}

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

.page-about .media img {
  display: block;
  max-width: 100%;
  height: auto;
}

.page-about .about-linkline {
  margin: 0;
  max-width: 52ch;
  font-size: 14px;
  line-height: 1.75;
  color: var(--noise);
}

.page-about .about-linkline a {
  color: var(--ink);
  text-decoration: underline;
  text-decoration-thickness: 2px;
  text-underline-offset: 3px;
}

.page-about .ledger {
  font-size: 15px;
  line-height: 1.75;
}

/* 深色面板 */
.page-about .about-panel {
  padding: 22px 20px;
  border: 3px solid var(--night);
  background: var(--night);
  color: var(--paper-on-night);
  box-shadow: var(--shadow-2);
}

.page-about .about-panel__eyebrow {
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--muted-on-night);
}

.page-about .about-chain {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 14px;
}

.page-about .about-chain li {
  display: grid;
  grid-template-columns: 28px 1fr;
  gap: 12px;
  align-items: start;
  font-size: 15px;
  line-height: 1.7;
}

.page-about .about-chain__n {
  display: grid;
  place-items: center;
  width: 28px;
  height: 28px;
  border: 2px solid var(--paper-on-night);
  border-radius: 50%;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1;
}

.page-about .about-chain li strong {
  color: var(--paper-on-night);
  font-weight: 800;
}

.page-about .about-panel__stamp {
  margin: 18px 0 0;
  padding-top: 14px;
  border-top: 2px solid var(--about-panel-line);
  font-size: 13px;
  line-height: 1.6;
  color: var(--muted-on-night);
}

.page-about .about-panel__stamp .stamp {
  color: var(--paper-on-night);
  border-color: var(--paper-on-night);
}

/* 时间轴 */
.page-about .timeline__jump {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  padding-bottom: 6px;
}

.page-about .timeline__jump-link {
  display: inline-flex;
  align-items: center;
  padding: 6px 14px;
  border: var(--border-1);
  border-radius: var(--radius-pill);
  background: var(--paper);
  font-family: var(--font-mono);
  font-size: 13px;
  text-decoration: none;
  color: var(--ink);
  transition: background-color 200ms var(--ease), box-shadow 200ms var(--ease);
}

.page-about .timeline__jump-link:hover,
.page-about .timeline__jump-link:focus-visible {
  outline: none;
  background: var(--turf);
  box-shadow: var(--shadow-1);
}

.page-about .timeline {
  position: relative;
  margin: 0;
  padding: 0 0 0 34px;
  list-style: none;
  display: grid;
  gap: 30px;
}

.page-about .timeline::before {
  content: "";
  position: absolute;
  left: 8px;
  top: 6px;
  bottom: 6px;
  width: 2px;
  background: var(--about-hair);
}

.page-about .timeline__item {
  position: relative;
  padding: 4px 0 4px 2px;
  transition: background-color 200ms var(--ease);
}

.page-about .timeline__item::before {
  content: "";
  position: absolute;
  left: -34px;
  top: 8px;
  width: 18px;
  height: 18px;
  border: 2px solid var(--ink);
  background: var(--ink);
}

.page-about .timeline__item:target {
  background: var(--turf);
  box-shadow: -10px 0 0 var(--turf), 10px 0 0 var(--turf);
}

.page-about .timeline__year {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 30px;
  font-weight: 700;
  letter-spacing: .01em;
  line-height: 1.1;
  color: var(--ink);
}

.page-about .timeline__stage {
  margin: 2px 0 8px;
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 800;
  letter-spacing: -.01em;
  line-height: 1.3;
}

.page-about .timeline__note {
  margin: 0;
  max-width: 44ch;
  font-size: 13px;
  line-height: 1.75;
  color: var(--noise);
}

/* 边界声明 */
.page-about .about-boundary-list {
  margin: 0;
  padding: 0;
  list-style: none;
  max-width: 52rem;
  border-top: var(--border-1);
}

.page-about .about-boundary-list li {
  display: grid;
  gap: 6px;
  padding: 18px 0;
  border-bottom: 2px solid var(--ash);
}

.page-about .about-boundary-list h3 {
  margin: 0;
  font-size: 18px;
  font-weight: 800;
  letter-spacing: -.01em;
  line-height: 1.4;
}

.page-about .about-boundary-list p {
  margin: 0;
  max-width: 54ch;
  font-size: 15px;
  line-height: 1.75;
  color: var(--ink);
}

/* 页尾行动区 */
.page-about .about-next {
  display: grid;
  gap: 12px;
  padding-top: 22px;
  border-top: var(--border-1);
}

.page-about .about-next__label {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--noise);
}

.page-about .about-next__links {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

/* 响应式 */
@media (min-width: 720px) {
  .page-about .about-hero {
    padding-block: 34px 52px;
  }

  .page-about .about-section {
    padding-block: 58px 66px;
  }

  .page-about .about-section__inner {
    gap: 28px;
  }

  .page-about .rule-legend {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 18px;
  }

  .page-about .about-panel {
    padding: 26px 24px;
  }
}

@media (min-width: 960px) {
  .page-about .about-split {
    grid-template-columns: minmax(0, 1.06fr) minmax(0, .94fr);
    gap: 44px;
    align-items: start;
  }

  .page-about .about-split--flip .about-split__figure {
    order: -1;
  }

  .page-about .timeline {
    padding-left: 0;
    gap: 4px;
  }

  .page-about .timeline::before {
    left: 50%;
    top: 0;
    bottom: 0;
    transform: translateX(-1px);
  }

  .page-about .timeline__item {
    width: 50%;
    padding: 8px 56px 8px 0;
  }

  .page-about .timeline__item::before {
    top: 16px;
    left: calc(100% - 9px);
  }

  .page-about .timeline__item:nth-child(even) {
    margin-left: 50%;
    padding: 8px 0 8px 56px;
  }

  .page-about .timeline__item:nth-child(even)::before {
    left: -9px;
  }

  .page-about .timeline__item:nth-child(odd) .timeline__year,
  .page-about .timeline__item:nth-child(odd) .timeline__stage,
  .page-about .timeline__item:nth-child(odd) .timeline__note {
    text-align: right;
    margin-left: auto;
  }

  .page-about .timeline__note {
    max-width: 38ch;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .rule-legend__item,
  .page-about .rule-legend__desc,
  .page-about .timeline__jump-link,
  .page-about .timeline__item {
    transition: none;
  }

  .page-about .rule-legend__item:hover,
  .page-about .rule-legend__item:focus-visible {
    transform: none;
  }
}