.page-about {
  --about-rule: var(--line-soft);
  --about-side-w: 176px;
  --about-measure: 60ch;
  max-width: var(--wrap);
  margin-inline: auto;
  padding: calc(var(--u) * 3) var(--gut) calc(var(--u) * 12);
  color: var(--ink);
  font-family: var(--sans);
}

/* 面包屑 */
.page-about .about-crumbs {
  font-family: var(--mono);
  font-size: .75rem;
  letter-spacing: .08em;
}
.page-about .about-crumbs ol {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 0;
  padding: 0;
  list-style: none;
  color: var(--ink-2);
}
.page-about .about-crumbs li + li::before {
  content: "/";
  margin-right: 10px;
  color: var(--line);
}
.page-about .about-crumbs a {
  color: var(--ink-2);
  text-decoration: none;
  border-bottom: 1px solid var(--about-rule);
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}
.page-about .about-crumbs a:hover,
.page-about .about-crumbs a:focus-visible {
  color: var(--focus);
  border-bottom-color: var(--focus);
}
.page-about .about-crumbs [aria-current="page"] {
  color: var(--orange);
}

/* 首屏 */
.page-about .about-hero {
  position: relative;
  margin-top: calc(var(--u) * 4);
  padding-bottom: calc(var(--u) * 5);
  border-bottom: 1px solid var(--about-rule);
}
.page-about .about-hero::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -1px;
  width: 72px;
  height: 4px;
  background: var(--orange);
}
.page-about .about-hero__kicker {
  margin: 0 0 20px;
  font-family: var(--mono);
  font-size: .75rem;
  letter-spacing: .16em;
  color: var(--orange);
}
.page-about .about-hero__title {
  margin: 0 0 22px;
  max-width: 12em;
  font-family: var(--serif);
  font-weight: 800;
  font-size: clamp(1.95rem, 5vw, 3.5rem);
  line-height: 1.2;
  letter-spacing: -.01em;
  color: var(--ink);
}
.page-about .about-hero__lede {
  margin: 0;
  max-width: 40em;
  font-size: 1rem;
  line-height: 1.85;
  color: var(--ink-2);
}
.page-about .about-hero__facts {
  display: flex;
  flex-wrap: wrap;
  gap: 20px 34px;
  margin: 34px 0 0;
  padding: 0;
  list-style: none;
}
.page-about .about-hero__facts li {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding-left: 14px;
  border-left: 2px solid var(--orange);
}
.page-about .about-hero__facts li:nth-child(2) {
  border-left-color: var(--teal);
}
.page-about .about-hero__facts li:nth-child(3) {
  border-left-color: var(--ochre);
}
.page-about .about-hero__num {
  font-family: var(--serif);
  font-weight: 800;
  font-size: 1.75rem;
  line-height: 1.1;
  color: var(--ink);
}
.page-about .about-hero__cap {
  font-family: var(--mono);
  font-size: .75rem;
  letter-spacing: .06em;
  color: var(--ink-2);
}

/* 章节流布局 */
.page-about .about-flow {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 36px;
  margin-top: calc(var(--u) * 7);
}

/* 侧边章节索引 */
.page-about .about-side {
  min-width: 0;
  padding-top: 14px;
  border-top: 8px solid var(--orange);
}
.page-about .about-side__tag {
  margin: 0;
  font-family: var(--mono);
  font-size: .6875rem;
  letter-spacing: .16em;
  color: var(--ink-2);
}
.page-about .about-side__list {
  display: flex;
  gap: 6px;
  margin: 12px 0 0;
  padding: 0 0 6px;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: thin;
  -webkit-overflow-scrolling: touch;
}
.page-about .about-side__list li {
  flex: 0 0 auto;
}
.page-about .about-side__link {
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding: 7px 10px;
  border-bottom: 2px solid transparent;
  background: var(--panel);
  color: var(--ink-2);
  font-size: .8125rem;
  line-height: 1.2;
  white-space: nowrap;
  text-decoration: none;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease), background-color var(--dur) var(--ease);
}
.page-about .about-side__link:hover,
.page-about .about-side__link:focus-visible {
  color: var(--ink);
  border-bottom-color: var(--teal);
  background: var(--paper-deep);
}
.page-about .about-side__link[data-active]:not([data-active="false"]),
.page-about .about-side__link[data-active="true"] {
  color: var(--orange);
  border-bottom-color: var(--orange);
  background: var(--paper);
}
.page-about .about-side__no {
  font-family: var(--mono);
  font-size: .6875rem;
  letter-spacing: .06em;
  color: var(--orange);
}
.page-about .about-side__top {
  display: inline-block;
  margin-top: 16px;
  font-family: var(--mono);
  font-size: .6875rem;
  letter-spacing: .1em;
  color: var(--ink-2);
  text-decoration: none;
  border-bottom: 1px solid var(--about-rule);
}
.page-about .about-side__top:hover,
.page-about .about-side__top:focus-visible {
  color: var(--focus);
  border-bottom-color: var(--focus);
}

/* 章节通用 */
.page-about .about-body {
  min-width: 0;
}
.page-about .about-sec {
  position: relative;
  margin-bottom: calc(var(--u) * 9);
  padding-top: calc(var(--u) * 2);
  border-top: 1px solid var(--about-rule);
}
.page-about .about-sec:last-child {
  margin-bottom: 0;
}
.page-about .about-sec__head {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 10px 14px;
  align-items: start;
  margin-bottom: 24px;
}
.page-about .about-sec__head h2 {
  margin: 0;
  font-family: var(--serif);
  font-weight: 700;
  font-size: clamp(1.35rem, 2.6vw, 1.95rem);
  line-height: 1.35;
  color: var(--ink);
}
.page-about .about-sec .chapter-no {
  display: inline-block;
  padding: 3px 8px;
  border: 1px solid var(--orange);
  border-radius: var(--r-sm);
  font-family: var(--mono);
  font-size: .6875rem;
  letter-spacing: .1em;
  color: var(--orange);
  white-space: nowrap;
}
.page-about .about-sec__note {
  grid-column: 1 / -1;
  margin: 0;
  font-family: var(--serif);
  font-size: .75rem;
  letter-spacing: .12em;
  color: var(--ochre);
  white-space: nowrap;
}

/* 正文段落，宽度交替 */
.page-about .about-prose {
  margin: 0 0 18px;
  max-width: var(--about-measure);
  font-size: .9688rem;
  line-height: 1.85;
  color: var(--ink-2);
}
.page-about .about-prose--wide {
  max-width: 68ch;
}
.page-about .about-prose--inset {
  max-width: 56ch;
}
.page-about .about-prose:last-child {
  margin-bottom: 0;
}

/* 图像 */
.page-about .about-figure {
  margin: 26px 0 26px;
}
.page-about .about-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  border-radius: var(--r-md);
  border: 1px solid var(--about-rule);
  background: var(--paper-deep);
  box-shadow: var(--shadow-card);
}
.page-about .about-figure figcaption {
  margin-top: 10px;
  font-family: var(--mono);
  font-size: .6875rem;
  letter-spacing: .05em;
  line-height: 1.6;
  color: var(--ink-2);
}
.page-about .about-figure--narrow {
  max-width: 100%;
}

/* 三段式版本号图解 */
.page-about .about-ver {
  margin: 26px 0;
  padding: 22px 18px 18px;
  border: 1px solid var(--about-rule);
  border-left: 6px solid var(--teal);
  border-radius: var(--r-md);
  background: var(--panel);
}
.page-about .about-ver__row {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  gap: 10px 12px;
}
.page-about .about-ver__seg {
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-width: 0;
}
.page-about .about-ver__val {
  font-family: var(--mono);
  font-weight: 600;
  font-size: 1.5rem;
  line-height: 1;
  letter-spacing: .02em;
  color: var(--ink);
}
.page-about .about-ver__seg--main .about-ver__val {
  color: var(--orange);
}
.page-about .about-ver__seg--sub .about-ver__val {
  color: var(--teal);
}
.page-about .about-ver__seg--batch .about-ver__val {
  color: var(--ochre);
}
.page-about .about-ver__txt {
  font-size: .75rem;
  line-height: 1.5;
  color: var(--ink-2);
}
.page-about .about-ver__dot {
  font-family: var(--mono);
  font-size: 1.5rem;
  line-height: 1;
  color: var(--line);
}
.page-about .about-ver figcaption {
  margin-top: 16px;
  padding-top: 12px;
  border-top: 1px dashed var(--about-rule);
  font-family: var(--mono);
  font-size: .6875rem;
  letter-spacing: .05em;
  color: var(--ink-2);
}

/* 变更标签 */
.page-about .about-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 0 0 22px;
  padding: 0;
  list-style: none;
}
.page-about .about-tag {
  padding: 5px 14px;
  border: 1px solid currentColor;
  border-radius: 999px;
  font-family: var(--mono);
  font-size: .75rem;
  letter-spacing: .1em;
}
.page-about .about-tag--new {
  color: var(--orange);
  background: rgba(231, 176, 138, .22);
}
.page-about .about-tag--adj {
  color: var(--teal);
  background: rgba(76, 107, 105, .1);
}
.page-about .about-tag--off {
  color: var(--ink);
  background: rgba(27, 25, 22, .07);
}
.page-about .about-tag--mov {
  color: var(--ochre);
  background: rgba(154, 107, 31, .12);
}

/* 整理规范折叠 */
.page-about .about-clause {
  margin: 24px 0 0;
  border: 1px solid var(--about-rule);
  border-radius: var(--r-md);
  background: var(--panel);
  overflow: hidden;
}
.page-about .about-clause summary {
  padding: 14px 18px;
  font-family: var(--mono);
  font-size: .8125rem;
  letter-spacing: .04em;
  color: var(--ink);
  cursor: pointer;
  list-style: none;
}
.page-about .about-clause summary::-webkit-details-marker {
  display: none;
}
.page-about .about-clause summary::before {
  content: "＋";
  margin-right: 10px;
  color: var(--orange);
}
.page-about .about-clause[open] summary::before {
  content: "－";
}
.page-about .about-clause summary:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: -2px;
}
.page-about .about-clause__body {
  padding: 0 18px 18px;
  border-top: 1px dashed var(--about-rule);
}
.page-about .about-clause__list {
  display: grid;
  gap: 14px;
  margin: 16px 0 0;
  padding: 0;
}
.page-about .about-clause__item {
  padding-left: 12px;
  border-left: 2px solid var(--teal);
}
.page-about .about-clause__item dt {
  font-family: var(--serif);
  font-weight: 700;
  font-size: .9375rem;
  color: var(--ink);
  margin-bottom: 4px;
}
.page-about .about-clause__item dd {
  margin: 0;
  font-size: .875rem;
  line-height: 1.75;
  color: var(--ink-2);
}

/* 五步流程 */
.page-about .about-steps {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0 0 26px;
  padding: 0;
  list-style: none;
}
.page-about .about-step {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  background: var(--paper-deep);
  border: 1px solid var(--about-rule);
  border-radius: var(--r-sm);
  font-size: .8125rem;
  color: var(--ink-2);
}
.page-about .about-step__no {
  font-family: var(--mono);
  font-size: .6875rem;
  color: var(--orange);
}

/* 时间轴 */
.page-about .about-timeline {
  position: relative;
  margin: 0;
  padding: 0 0 0 32px;
  list-style: none;
  display: grid;
  gap: 28px;
}
.page-about .about-timeline::before {
  content: "";
  position: absolute;
  left: 4px;
  top: 10px;
  bottom: 10px;
  width: 2px;
  background: var(--about-rule);
}
.page-about .about-tl {
  position: relative;
  padding-left: 4px;
}
.page-about .about-tl::before {
  content: "";
  position: absolute;
  left: -33px;
  top: 6px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--paper);
  border: 2px solid var(--orange);
  box-sizing: border-box;
}
.page-about .about-tl:nth-child(even)::before {
  border-color: var(--teal);
}
.page-about .about-tl__year {
  margin: 0 0 4px;
  font-family: var(--mono);
  font-size: 1.0625rem;
  font-weight: 600;
  letter-spacing: .06em;
  color: var(--orange);
}
.page-about .about-tl:nth-child(even) .about-tl__year {
  color: var(--teal);
}
.page-about .about-tl__title {
  margin: 0 0 6px;
  font-family: var(--serif);
  font-weight: 700;
  font-size: 1.0625rem;
  color: var(--ink);
}
.page-about .about-tl__desc {
  margin: 0;
  max-width: 46em;
  font-size: .9063rem;
  line-height: 1.8;
  color: var(--ink-2);
}

/* 场景卡片 */
.page-about .about-scenes {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
  margin: 0 0 24px;
  padding: 0;
  list-style: none;
}
.page-about .about-scene {
  position: relative;
  padding: 20px 18px 20px 22px;
  background: var(--panel);
  border: 1px solid var(--about-rule);
  border-radius: var(--r-md);
}
.page-about .about-scene::before {
  content: "";
  position: absolute;
  left: 0;
  top: 18px;
  bottom: 18px;
  width: 4px;
  background: var(--orange);
  border-radius: 0 var(--r-sm) var(--r-sm) 0;
}
.page-about .about-scene:nth-child(2)::before {
  background: var(--teal);
}
.page-about .about-scene:nth-child(3)::before {
  background: var(--ochre);
}
.page-about .about-scene:nth-child(4)::before {
  background: var(--ink);
}
.page-about .about-scene__no {
  display: block;
  margin-bottom: 6px;
  font-family: var(--mono);
  font-size: .6875rem;
  letter-spacing: .1em;
  color: var(--line);
}
.page-about .about-scene__title {
  margin: 0 0 8px;
  font-family: var(--serif);
  font-weight: 700;
  font-size: 1.0625rem;
  color: var(--ink);
}
.page-about .about-scene p {
  margin: 0;
  font-size: .9063rem;
  line-height: 1.78;
  color: var(--ink-2);
}

/* 成果数据 */
.page-about .about-metrics {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 0 0 26px;
  padding: 0;
  list-style: none;
  background: var(--about-rule);
  border: 1px solid var(--about-rule);
  border-radius: var(--r-md);
  overflow: hidden;
}
.page-about .about-metrics li {
  background: var(--panel);
  padding: 18px 16px;
}
.page-about .about-metrics__num {
  font-family: var(--serif);
  font-weight: 800;
  font-size: 1.75rem;
  line-height: 1;
  color: var(--orange);
}
.page-about .about-metrics li:nth-child(2) .about-metrics__num,
.page-about .about-metrics li:nth-child(4) .about-metrics__num {
  color: var(--teal);
}
.page-about .about-metrics li:nth-child(3) .about-metrics__num,
.page-about .about-metrics li:nth-child(5) .about-metrics__num {
  color: var(--ochre);
}
.page-about .about-metrics__unit {
  margin-left: 4px;
  font-family: var(--mono);
  font-size: .75rem;
  color: var(--ink-2);
}
.page-about .about-metrics p {
  margin: 10px 0 0;
  font-size: .8125rem;
  line-height: 1.7;
  color: var(--ink-2);
}

/* 结尾入口 */
.page-about .about-cta {
  margin-top: 30px;
  padding: 24px 20px;
  border: 1px solid var(--about-rule);
  border-top: 8px solid var(--orange);
  border-radius: var(--r-md);
  background: var(--paper-deep);
}
.page-about .about-cta__lead {
  margin: 0 0 18px;
  max-width: 44em;
  font-family: var(--serif);
  font-size: 1.0625rem;
  line-height: 1.7;
  color: var(--ink);
}
.page-about .about-cta__links {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

/* 焦点可见性 */
.page-about a:focus-visible,
.page-about summary:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 3px;
}

@media (min-width: 640px) {
  .page-about .about-figure--narrow {
    max-width: 88%;
    margin-left: auto;
  }
  .page-about .about-metrics {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
  .page-about .about-scenes {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 16px;
  }
  .page-about .about-scene:nth-child(1),
  .page-about .about-scene:nth-child(4) {
    grid-column: 1 / -1;
  }
  .page-about .about-cta {
    padding: 30px 28px;
  }
}

@media (min-width: 900px) {
  .page-about .about-flow {
    grid-template-columns: var(--about-side-w) minmax(0, 1fr);
    gap: 56px;
    align-items: start;
  }
  .page-about .about-side {
    position: sticky;
    top: 104px;
  }
  .page-about .about-side__list {
    flex-direction: column;
    gap: 0;
    overflow: visible;
    padding-bottom: 0;
  }
  .page-about .about-side__list li {
    flex: 1 1 auto;
    border-bottom: 1px solid var(--about-rule);
  }
  .page-about .about-side__link {
    width: 100%;
    padding: 10px 8px;
    background: transparent;
    border-bottom-width: 2px;
    box-sizing: border-box;
  }
  .page-about .about-side__link:hover,
  .page-about .about-side__link:focus-visible {
    background: var(--panel);
  }
  .page-about .about-side__link[data-active]:not([data-active="false"]),
  .page-about .about-side__link[data-active="true"] {
    background: var(--panel);
  }
  .page-about .about-sec__head {
    grid-template-columns: auto minmax(0, 1fr) auto;
    gap: 10px 18px;
    margin-bottom: 28px;
  }
  .page-about .about-sec__note {
    grid-column: 3;
    writing-mode: vertical-rl;
    text-orientation: upright;
    height: 6.5em;
    justify-self: end;
  }
  .page-about .about-prose {
    font-size: 1rem;
  }
  .page-about .about-prose--inset {
    margin-left: 7%;
  }
  .page-about .about-tl {
    padding-left: 10px;
  }
  .page-about .about-tl:nth-child(even) {
    margin-left: 42px;
  }
  .page-about .about-tl:nth-child(odd) {
    margin-right: 42px;
  }
  .page-about .about-ver {
    padding: 28px 26px 22px;
  }
  .page-about .about-ver__row {
    gap: 14px 18px;
  }
  .page-about .about-ver__val {
    font-size: 2rem;
  }
  .page-about .about-ver__dot {
    font-size: 2rem;
  }
}

@media (min-width: 1080px) {
  .page-about .about-hero__title {
    max-width: 11em;
  }
  .page-about .about-sec {
    margin-bottom: calc(var(--u) * 11);
  }
  .page-about .about-metrics li {
    padding: 22px 20px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-side__link,
  .page-about .about-crumbs a {
    transition: none;
  }
}
<<<END>>>