.page-about {
  --about-measure: 34em;
  --about-gap: clamp(20px, 3vw, 34px);
  --about-rail-gap: clamp(14px, 2vw, 22px);
  display: block;
}

.page-about .breadcrumb {
  padding-top: clamp(16px, 3vw, 28px);
}

.page-about .breadcrumb__link {
  color: var(--yh-mist);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color var(--yh-dur-1) var(--yh-ease), color var(--yh-dur-1) var(--yh-ease);
}

.page-about .breadcrumb__link:hover,
.page-about .breadcrumb__link:focus-visible {
  color: var(--yh-focus);
  border-bottom-color: var(--yh-focus);
}

.page-about .breadcrumb__here {
  color: var(--yh-paper);
}

.page-about .tone-coral { color: var(--yh-coral); text-decoration: none; border-bottom: 1px solid var(--yh-coral); }
.page-about .tone-amber { color: var(--yh-amber); text-decoration: none; border-bottom: 1px solid var(--yh-amber); }
.page-about .tone-clay { color: var(--yh-clay); text-decoration: none; border-bottom: 1px solid var(--yh-clay); }

.page-about .tone-coral:hover,
.page-about .tone-amber:hover,
.page-about .tone-clay:hover,
.page-about .tone-coral:focus-visible,
.page-about .tone-amber:focus-visible,
.page-about .tone-clay:focus-visible {
  color: var(--yh-focus);
  border-bottom-color: var(--yh-focus);
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  padding-top: clamp(22px, 4vw, 44px);
  padding-bottom: clamp(38px, 6vw, 76px);
}

.page-about .about-hero__kicker {
  margin: 0 0 18px;
  color: var(--yh-mist);
  letter-spacing: .22em;
}

.page-about .about-hero__title {
  margin: 0 0 clamp(20px, 3vw, 30px);
  font-family: var(--yh-font-head);
  font-weight: 900;
  font-size: var(--yh-fs-display);
  line-height: 1.1;
  letter-spacing: -.02em;
  color: var(--yh-paper);
  max-width: 12em;
}

.page-about .about-hero__lede {
  margin: 0;
  max-width: var(--about-measure);
  font-size: clamp(1.03rem, 1.6vw, 1.2rem);
  line-height: 1.8;
  color: var(--yh-mist);
}

.page-about .about-hero__stages {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 26px;
  list-style: none;
  margin: clamp(26px, 4vw, 44px) 0 0;
  padding: clamp(18px, 2.5vw, 24px) 0 0;
  border-top: 1px solid var(--yh-line);
}

.page-about .about-hero__stage {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-size: .8125rem;
  letter-spacing: .18em;
  color: var(--yh-mist);
}

.page-about .about-hero__dot {
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
}

.page-about .about-hero__dot--coral { background: var(--yh-coral); }
.page-about .about-hero__dot--celadon { background: var(--yh-celadon); }
.page-about .about-hero__dot--amber { background: var(--yh-amber); }
.page-about .about-hero__dot--mist { background: var(--yh-mist); }

.page-about .about-hero::after {
  content: "";
  display: block;
  width: min(300px, 56%);
  height: 4px;
  margin-top: clamp(26px, 4vw, 40px);
  background: linear-gradient(90deg, var(--yh-coral), var(--yh-mid) 52%, var(--yh-amber));
}

/* ---------- 章节通用 ---------- */
.page-about .about-sec {
  margin-bottom: var(--about-gap);
}

.page-about .about-sec__inner {
  position: relative;
  background: var(--yh-board);
  border: 1px solid var(--yh-line);
  border-radius: 2px;
  color: var(--yh-paper);
  padding: clamp(26px, 4vw, 34px) clamp(18px, 3.2vw, 26px);
}

.page-about .about-sec__h2 {
  margin: 0 0 clamp(14px, 2vw, 22px);
  font-family: var(--yh-font-head);
  font-weight: 800;
  font-size: var(--yh-fs-section);
  line-height: 1.2;
  letter-spacing: -.012em;
}

.page-about .about-sec__h2--wide {
  max-width: 22em;
  color: var(--yh-paper);
}

.page-about .about-sec__body .prose,
.page-about .about-maint__body .prose,
.page-about .about-qr__body .prose {
  max-width: var(--about-measure);
}

.page-about .prose p {
  margin: 0 0 1.4em;
  line-height: 1.8;
}

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

.page-about .about-sec__num {
  display: none;
  position: absolute;
  left: clamp(12px, 1.8vw, 20px);
  bottom: clamp(20px, 3vw, 30px);
  font-family: var(--yh-font-num);
  font-size: .75rem;
  letter-spacing: .2em;
  color: currentColor;
  opacity: .4;
}

.page-about .about-sec__stage {
  display: none;
  position: absolute;
  left: clamp(10px, 1.8vw, 20px);
  top: clamp(30px, 4vw, 44px);
  writing-mode: vertical-rl;
  letter-spacing: .32em;
  margin: 0;
  color: var(--yh-mist);
}

/* ---------- 纸面章节 ---------- */
.page-about .about-sec--paper .about-sec__inner {
  background: var(--yh-paper);
  border-color: var(--yh-paper-edge);
  color: var(--yh-ink-text);
  box-shadow: 8px 8px 0 0 rgba(227, 218, 202, .55);
}

.page-about .about-sec--paper .about-sec__h2 {
  color: var(--yh-ink);
}

.page-about .about-sec--paper .about-sec__stage {
  color: var(--yh-clay);
}

.page-about .about-sec--paper .prose a.tone-amber {
  color: var(--yh-amber-dp);
  border-bottom-color: var(--yh-amber-dp);
}

.page-about .about-sec--paper .prose a.tone-amber:hover,
.page-about .about-sec--paper .prose a.tone-amber:focus-visible {
  color: var(--yh-clay);
  border-bottom-color: var(--yh-clay);
}

/* ---------- 图与说明 ---------- */
.page-about .about-figure {
  margin: clamp(22px, 3vw, 32px) 0 0;
}

.page-about .about-figure .media-frame,
.page-about .about-maint__figure .media-frame,
.page-about .about-qr__figure .media-frame {
  max-width: 100%;
}

.page-about .media-frame img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.page-about .media-frame {
  position: relative;
  overflow: hidden;
  background: var(--yh-ink);
  border: 1px solid var(--yh-line);
  border-radius: 2px;
}

.page-about .about-sec--paper .media-frame {
  border-color: var(--yh-paper-edge);
}

.page-about .media-frame__note {
  display: block;
  margin: 10px 0 0;
  font-size: var(--yh-fs-note);
  letter-spacing: .08em;
  color: var(--yh-mist);
}

.page-about .about-sec--paper .media-frame__note {
  color: var(--yh-clay);
}

/* ---------- 时间线 ---------- */
.page-about .about-sec--rail {
  margin-top: clamp(40px, 6vw, 72px);
}

.page-about .about-rail__lede {
  margin: 0;
  max-width: var(--about-measure);
  font-size: var(--yh-fs-body);
  line-height: 1.8;
  color: var(--yh-mist);
}

.page-about .about-rail {
  margin-top: clamp(18px, 3vw, 30px);
  overflow-x: auto;
  overflow-y: hidden;
  scroll-snap-type: x proximity;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: thin;
  scrollbar-color: var(--yh-line) transparent;
  padding-bottom: 8px;
}

.page-about .about-rail:focus-visible {
  outline: 2px solid var(--yh-focus);
  outline-offset: 4px;
}

.page-about .about-rail__list {
  list-style: none;
  margin: 0;
  padding: 6px var(--yh-pad) 22px;
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: minmax(248px, 76vw);
  gap: var(--about-rail-gap);
  align-items: stretch;
}

.page-about .about-node {
  scroll-snap-align: start;
  position: relative;
  padding: 0 0 22px;
  background: linear-gradient(180deg, rgba(16, 32, 58, .92), rgba(10, 22, 38, .92));
  border: 1px solid var(--yh-line);
  border-radius: 2px;
  padding-left: 20px;
  padding-right: 20px;
  transition: transform var(--yh-dur-1) var(--yh-ease), border-color var(--yh-dur-1) var(--yh-ease);
}

.page-about .about-node:hover {
  transform: translateY(-2px);
  border-color: var(--yh-amber);
}

.page-about .about-node__head {
  position: relative;
  border-top: 2px solid var(--yh-line);
  margin-top: 22px;
  padding-top: 22px;
}

.page-about .about-node__head::before {
  content: "";
  position: absolute;
  top: -7px;
  left: 0;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--yh-paper);
  border: 2px solid var(--yh-amber);
}

.page-about .about-node__ver {
  font-family: var(--yh-font-num);
  font-size: .8125rem;
  letter-spacing: .2em;
  color: var(--yh-amber);
}

.page-about .about-node__title {
  margin: 10px 0 12px;
  font-family: var(--yh-font-head);
  font-weight: 800;
  font-size: var(--yh-fs-sub);
  line-height: 1.25;
  color: var(--yh-paper);
}

.page-about .about-node__text {
  margin: 0;
  font-size: var(--yh-fs-body);
  line-height: 1.8;
  color: var(--yh-mist);
}

/* ---------- 维护 5/7 分栏 ---------- */
.page-about .about-maint {
  display: grid;
  gap: clamp(20px, 3vw, 34px);
  align-items: start;
}

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

/* ---------- 二维码区块 ---------- */
.page-about .about-qr {
  display: grid;
  gap: clamp(24px, 3.5vw, 42px);
  align-items: start;
}

.page-about .about-qr__note {
  display: inline-block;
  margin: 0 0 12px;
  color: var(--yh-clay);
}

.page-about .about-qr__contact {
  margin: clamp(20px, 3vw, 28px) 0 0;
  padding: 0;
  display: grid;
  gap: 12px;
}

.page-about .about-qr__row {
  display: grid;
  grid-template-columns: 5.5em 1fr;
  gap: 6px 12px;
  align-items: baseline;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--yh-paper-edge);
}

.page-about .about-qr__row:last-child {
  border-bottom: none;
  padding-bottom: 0;
}

.page-about .about-qr__k {
  font-size: var(--yh-fs-note);
  letter-spacing: .16em;
  color: var(--yh-clay);
}

.page-about .about-qr__v {
  margin: 0;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
}

.page-about .about-qr__val {
  font-family: var(--yh-font-num);
  font-size: .95rem;
  color: var(--yh-ink);
  word-break: break-word;
}

.page-about .about-qr__row:nth-child(3) .about-qr__val {
  font-family: var(--yh-font-body);
}

.page-about .about-qr__more {
  margin: clamp(18px, 2.5vw, 24px) 0 0;
  font-size: var(--yh-fs-note);
  line-height: 1.9;
  color: var(--yh-ink-soft);
  max-width: var(--about-measure);
}

.page-about .copy-btn {
  appearance: none;
  cursor: pointer;
  font: inherit;
  font-size: var(--yh-fs-note);
  letter-spacing: .1em;
  padding: 5px 12px;
  border-radius: 2px;
  border: 1px solid var(--yh-clay);
  background: transparent;
  color: var(--yh-clay);
  transition: background var(--yh-dur-1) var(--yh-ease), color var(--yh-dur-1) var(--yh-ease);
}

.page-about .copy-btn:hover,
.page-about .copy-btn:focus-visible {
  background: var(--yh-clay);
  color: var(--yh-paper);
}

.page-about .about-qr__figure {
  margin: 0;
  position: relative;
}

.page-about .about-qr__code {
  width: 124px;
  height: 124px;
  margin-top: 16px;
  border-radius: 4px;
  background-color: #FFFFFF;
  background-image:
    linear-gradient(var(--yh-ink-text) 0 0),
    linear-gradient(var(--yh-ink-text) 0 0),
    linear-gradient(var(--yh-ink-text) 0 0),
    repeating-conic-gradient(var(--yh-ink-text) 0deg 90deg, transparent 90deg 180deg);
  background-size: 32px 32px, 32px 32px, 32px 32px, 16px 16px;
  background-position: 0 0, 100% 0, 0 100%, 0 0;
  background-repeat: no-repeat, no-repeat, no-repeat, repeat;
  border: 6px solid #FFFFFF;
  outline: 1px solid var(--yh-paper-edge);
  box-shadow: 4px 4px 0 0 rgba(227, 218, 202, .7);
}

/* ---------- 下一步 ---------- */
.page-about .about-sec--next {
  margin-top: clamp(36px, 5vw, 64px);
  margin-bottom: clamp(48px, 7vw, 96px);
}

.page-about .about-next {
  display: grid;
  gap: clamp(14px, 2vw, 22px);
  margin-top: clamp(20px, 3vw, 32px);
}

.page-about .about-next__card {
  position: relative;
  display: grid;
  gap: 8px;
  padding: clamp(20px, 3vw, 28px) clamp(20px, 3vw, 30px);
  text-decoration: none;
  border: 1px solid var(--yh-line);
  border-left-width: 6px;
  border-radius: 2px;
  background: var(--yh-board);
  transition: transform var(--yh-dur-1) var(--yh-ease), box-shadow var(--yh-dur-1) var(--yh-ease);
}

.page-about .about-next__card--coral {
  border-left-color: var(--yh-coral);
}

.page-about .about-next__card--celadon {
  border-left-color: var(--yh-celadon);
}

.page-about .about-next__card:hover,
.page-about .about-next__card:focus-visible {
  transform: translateY(-2px);
  box-shadow: 6px 6px 0 0 rgba(39, 64, 94, .7);
}

.page-about .about-next__label {
  font-family: var(--yh-font-head);
  font-weight: 800;
  font-size: var(--yh-fs-sub);
  color: var(--yh-paper);
  line-height: 1.2;
}

.page-about .about-next__desc {
  font-size: var(--yh-fs-body);
  line-height: 1.8;
  color: var(--yh-mist);
  max-width: 30em;
}

.page-about .about-next__go {
  position: absolute;
  right: clamp(18px, 3vw, 26px);
  bottom: clamp(16px, 2.5vw, 24px);
  font-size: 1.35rem;
  color: var(--yh-focus);
}

.page-about .about-next__card--coral .about-next__go { color: var(--yh-coral); }
.page-about .about-next__card--celadon .about-next__go { color: var(--yh-celadon-lt); }

/* ---------- 中等屏幕 ---------- */
@media (min-width: 700px) {
  .page-about .about-sec__inner {
    padding: clamp(34px, 4.4vw, 56px) clamp(24px, 3.4vw, 48px) clamp(34px, 4.4vw, 56px) clamp(56px, 7vw, 88px);
  }

  .page-about .about-sec__num,
  .page-about .about-sec__stage {
    display: block;
  }

  .page-about .about-rail__list {
    grid-auto-columns: clamp(252px, 32vw, 340px);
    padding-left: max(var(--yh-pad), calc((100vw - var(--yh-max)) / 2 + var(--yh-pad)));
    padding-right: max(var(--yh-pad), calc((100vw - var(--yh-max)) / 2 + var(--yh-pad)));
  }

  .page-about .about-next {
    grid-template-columns: 1fr 1fr;
  }
}

/* ---------- 桌面分栏 ---------- */
@media (min-width: 860px) {
  .page-about .about-maint {
    grid-template-columns: 5fr 7fr;
    gap: clamp(24px, 3.5vw, 44px);
  }

  .page-about .about-maint__figure {
    position: sticky;
    top: 108px;
  }

  .page-about .about-qr {
    grid-template-columns: 6fr 5fr;
    gap: clamp(28px, 4vw, 52px);
  }
}

/* ---------- 降低动效偏好 ---------- */
@media (prefers-reduced-motion: reduce) {
  .page-about .about-node,
  .page-about .about-next__card,
  .page-about .copy-btn {
    transition: none;
  }

  .page-about .about-node:hover,
  .page-about .about-next__card:hover,
  .page-about .about-next__card:focus-visible {
    transform: none;
  }

  .page-about .about-rail {
    scroll-behavior: auto;
  }
}
<<<END>>>