.page-about {
  --about-gap: clamp(64px, 8.5vw, 128px);
  --about-rail: 96px;
  --about-dot: 11px;
}

/* ---------- 首屏 ---------- */
.page-about .about-open {
  position: relative;
  padding: clamp(40px, 6vw, 84px) 0 clamp(32px, 4.5vw, 60px);
  background:
    radial-gradient(118% 88% at 10% -6%, rgba(0, 229, 199, 0.09), transparent 60%),
    radial-gradient(90% 70% at 96% 8%, rgba(196, 154, 108, 0.07), transparent 62%);
}

.page-about .about-open .crumbs {
  margin-bottom: clamp(28px, 5vw, 54px);
}

.page-about .about-open .kicker {
  display: block;
  margin: 0 0 20px;
}

.page-about .about-open .display {
  max-width: 15em;
  margin: 0 0 clamp(20px, 3vw, 30px);
}

.page-about .about-open .lede {
  max-width: 33em;
  margin: 0;
}

/* ---------- 章节跳转 ---------- */
.page-about .about-jump {
  margin-top: clamp(34px, 5vw, 62px);
  border-top: 1px solid var(--line);
}

.page-about .about-jump__list {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .about-jump__link {
  display: flex;
  align-items: baseline;
  gap: 12px;
  padding: 14px 8px 14px 0;
  border-bottom: 1px solid var(--line-soft);
  color: var(--text);
  font-size: 15px;
  line-height: 1.5;
  text-decoration: none;
  transition: color var(--t) ease, background-color var(--t) ease, padding-left var(--t) ease;
}

.page-about .about-jump__link:hover,
.page-about .about-jump__link:focus-visible {
  color: var(--hi);
  background-color: rgba(0, 229, 199, 0.06);
  padding-left: 8px;
}

.page-about .about-jump__n {
  flex: none;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--signal);
}

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

/* ---------- 章节容器 ---------- */
.page-about .about-sec {
  padding: var(--about-gap) 0 0;
}

.page-about .about-sec:last-of-type {
  padding-bottom: var(--about-gap);
}

.page-about .about-row {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
}

.page-about .about-rail {
  position: relative;
  display: flex;
  align-items: center;
  gap: 12px;
  padding-left: 0;
}

.page-about .about-rail__num {
  position: relative;
  z-index: 1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  flex: none;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--signal);
  background: var(--ink);
  border: 1px solid var(--line-signal);
}

.page-about .about-rail__line {
  position: absolute;
  left: 14px;
  top: 0;
  bottom: 0;
  width: 1px;
  background: linear-gradient(180deg, var(--line-signal) 0%, var(--line-soft) 78%, transparent 100%);
}

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

.page-about .about-col .h2 {
  margin: 0 0 clamp(18px, 2.4vw, 26px);
}

.page-about .about-col .prose {
  max-width: 34em;
}

.page-about .about-col .prose p + p {
  margin-top: 1.15em;
}

.page-about .about-intro {
  max-width: 34em;
  margin: 0 0 clamp(28px, 4vw, 46px);
  color: var(--muted);
  font-size: 17px;
  line-height: 1.85;
}

.page-about .about-more {
  max-width: 34em;
  margin: clamp(24px, 3.4vw, 38px) 0 0;
  padding-top: clamp(18px, 2.6vw, 26px);
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 16px;
  line-height: 1.85;
}

.page-about .about-note {
  max-width: 34em;
  margin-top: clamp(30px, 4.2vw, 48px);
  padding: clamp(20px, 3vw, 30px) clamp(20px, 3vw, 32px);
  background: rgba(19, 41, 75, 0.5);
  border-left: 2px solid var(--signal);
  box-shadow: var(--shadow);
}

.page-about .about-note p {
  margin: 0;
  color: var(--text);
  font-size: 16px;
  line-height: 1.9;
}

.page-about .about-note p + p {
  margin-top: 14px;
  color: var(--muted);
}

/* ---------- 阶段列表 ---------- */
.page-about .phase-list {
  position: relative;
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line);
}

.page-about .phase-list::before {
  content: "";
  position: absolute;
  left: 5px;
  top: 22px;
  bottom: 22px;
  width: 1px;
  background: var(--line-soft);
}

.page-about .phase {
  position: relative;
  padding: clamp(22px, 3.2vw, 34px) 0 clamp(22px, 3.2vw, 34px) 34px;
  border-bottom: 1px solid var(--line-soft);
  transition: background-color var(--t) ease;
}

.page-about .phase:hover,
.page-about .phase:focus-within {
  background-color: rgba(0, 229, 199, 0.035);
}

.page-about .phase__dot {
  position: absolute;
  left: 0;
  top: calc(clamp(22px, 3.2vw, 34px) + 8px);
  width: var(--about-dot);
  height: var(--about-dot);
  background: var(--ink);
  border: 1px solid var(--signal);
  transition: background-color var(--t) ease, box-shadow var(--t) ease;
}

.page-about .phase:hover .phase__dot,
.page-about .phase:focus-within .phase__dot {
  background: var(--signal);
  box-shadow: 0 0 0 5px rgba(0, 229, 199, 0.14);
}

.page-about .phase__code {
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--muted);
}

.page-about .phase__title {
  margin: 0 0 12px;
  font-family: var(--font-display);
  font-size: clamp(1.18rem, 2.1vw, 1.5rem);
  font-weight: 700;
  line-height: 1.45;
  color: var(--hi);
  letter-spacing: -0.01em;
}

.page-about .phase__body {
  max-width: 34em;
  margin: 0;
  color: var(--text);
  font-size: 17px;
  line-height: 1.85;
}

.page-about .phase__note {
  max-width: 34em;
  max-height: 0;
  margin: 0;
  overflow: hidden;
  opacity: 0;
  color: var(--signal);
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.8;
  letter-spacing: 0.04em;
  transition: max-height 260ms ease, opacity 260ms ease, margin-top 260ms ease;
}

.page-about .phase:hover .phase__note,
.page-about .phase:focus-within .phase__note {
  max-height: 5.5rem;
  margin-top: 14px;
  opacity: 1;
}

/* ---------- 通用图注 ---------- */
.page-about .figure {
  margin: clamp(30px, 4.4vw, 50px) 0 0;
}

.page-about .figure__cap {
  margin-top: 12px;
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 12.5px;
  line-height: 1.7;
  letter-spacing: 0.03em;
}

.page-about .figure__media img {
  display: block;
  width: 100%;
  height: auto;
  max-width: 100%;
  object-fit: cover;
}

.page-about .about-fig {
  max-width: 46rem;
}

/* ---------- 版本对照 ---------- */
.page-about .about-compare {
  margin: clamp(28px, 4vw, 44px) 0 0;
  max-width: 48rem;
}

.page-about .about-compare .compare {
  display: block;
  border-top: 1px solid var(--line);
}

.page-about .about-compare .compare__row {
  display: grid;
  grid-template-columns: 1fr;
  gap: 6px 22px;
  padding: 16px 0;
  border-bottom: 1px solid var(--line-soft);
}

.page-about .about-compare .compare__row:first-child {
  padding: 12px 0 10px;
  border-bottom-color: var(--line-signal);
}

.page-about .about-compare .compare__dim {
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.08em;
  line-height: 1.7;
}

.page-about .about-compare .compare__old,
.page-about .about-compare .compare__new {
  font-size: 15.5px;
  line-height: 1.7;
}

.page-about .about-compare .compare__old {
  color: var(--muted);
}

.page-about .about-compare .compare__new {
  color: var(--text);
}

.page-about .about-compare .compare__row:first-child .compare__old {
  color: var(--ochre);
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.08em;
}

.page-about .about-compare .compare__row:first-child .compare__new {
  color: var(--signal);
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.08em;
}

/* ---------- 覆盖范围 ---------- */
.page-about .about-cover {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(26px, 4vw, 40px);
  align-items: start;
}

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

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

.page-about .about-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin-bottom: clamp(26px, 3.6vw, 40px);
  background: var(--line-soft);
  border: 1px solid var(--line-soft);
}

.page-about .about-stats .stat {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 18px 16px;
  background: var(--ink);
}

.page-about .about-stats .stat__num {
  font-family: var(--font-display);
  font-size: clamp(1.7rem, 4vw, 2.4rem);
  font-weight: 900;
  line-height: 1;
  color: var(--signal);
}

.page-about .about-stats .stat__label {
  color: var(--muted);
  font-size: 13.5px;
  line-height: 1.6;
}

/* ---------- 归档 ---------- */
.page-about .about-arc {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(26px, 4vw, 44px);
  margin-top: clamp(28px, 4vw, 44px);
}

.page-about .arc-list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .arc-list__item {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 16px 0;
  border-bottom: 1px solid var(--line-soft);
}

.page-about .arc-list__item:first-child {
  border-top: 1px solid var(--line);
}

.page-about .arc-list .arch-tag {
  align-self: flex-start;
  padding: 5px 10px;
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.08em;
  color: var(--ochre);
  background: rgba(196, 154, 108, 0.08);
  border: 1px dashed var(--ochre);
  border-right: 1px solid var(--ochre-deep);
  word-break: break-all;
}

.page-about .arc-list__desc {
  color: var(--muted);
  font-size: 14px;
  line-height: 1.65;
}

.page-about .about-arc__hint {
  max-width: 34em;
  margin: 18px 0 0;
  color: var(--muted);
  font-size: 14px;
  line-height: 1.8;
}

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

/* ---------- 焦点样式 ---------- */
.page-about .about-jump__link:focus-visible,
.page-about .u-link:focus-visible {
  outline: 2px solid var(--signal);
  outline-offset: 2px;
}

/* ---------- 响应式 ---------- */
@media (min-width: 640px) {
  .page-about .about-jump__list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    column-gap: 28px;
  }

  .page-about .about-stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .about-compare .compare__row {
    grid-template-columns: 132px minmax(0, 1fr) minmax(0, 1fr);
    align-items: start;
    gap: 6px 24px;
    padding: 18px 0;
  }
}

@media (min-width: 900px) {
  .page-about .about-row {
    grid-template-columns: var(--about-rail) minmax(0, 1fr);
    gap: 0 40px;
  }

  .page-about .about-rail {
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    padding-top: 4px;
  }

  .page-about .about-jump__list {
    grid-template-columns: repeat(5, minmax(0, 1fr));
    column-gap: 24px;
  }

  .page-about .about-jump__link {
    border-bottom: 2px solid transparent;
  }

  .page-about .about-jump__link:hover,
  .page-about .about-jump__link:focus-visible {
    border-bottom-color: var(--signal);
    padding-left: 0;
  }

  .page-about .about-cover {
    grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
  }

  .page-about .about-arc {
    grid-template-columns: minmax(0, 6fr) minmax(0, 5fr);
    align-items: start;
  }

  .page-about .about-arc__fig {
    margin-top: 4px;
  }
}

@media (min-width: 1180px) {
  .page-about {
    --about-rail: 112px;
  }
}

@media (max-width: 899px) {
  .page-about .about-rail__line {
    display: none;
  }

  .page-about .about-rail__num {
    background: rgba(0, 229, 199, 0.08);
  }
}
<<<END>>>