.page-about {
  background-color: var(--ice-bg);
  color: var(--ink);
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  isolation: isolate;
  background-color: var(--pitch);
  color: var(--chalk);
  padding-block: clamp(40px, 8vw, 96px) clamp(36px, 6vw, 72px);
}
.page-about .about-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background-image:
    linear-gradient(to right, rgba(185, 214, 227, 0.09) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(185, 214, 227, 0.09) 1px, transparent 1px),
    linear-gradient(to right, rgba(185, 214, 227, 0.045) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(185, 214, 227, 0.045) 1px, transparent 1px);
  background-size: 96px 96px, 96px 96px, 8px 8px, 8px 8px;
}
.page-about .about-hero__inner {
  max-width: var(--content);
  margin-inline: auto;
  padding-inline: var(--pad);
}
.page-about .about-hero__kicker {
  margin: 0 0 18px;
  font-family: var(--font-num);
  font-size: 12px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--pitch-moss);
}
.page-about .about-hero__title {
  margin: 0 0 10px;
  font-family: var(--font-head);
  font-size: clamp(2.1rem, 6.6vw, 4.4rem);
  line-height: 1.06;
  letter-spacing: -0.01em;
  color: var(--chalk);
}
.page-about .about-hero__sub {
  margin: 0 0 26px;
  font-family: var(--font-head);
  font-size: clamp(1rem, 2.2vw, 1.45rem);
  line-height: 1.3;
  color: var(--pitch-moss);
}
.page-about .about-hero__lead {
  max-width: 62ch;
  margin: 0 0 38px;
  font-size: 1rem;
  line-height: 1.85;
  color: rgba(244, 247, 245, 0.86);
}
.page-about .about-hero__stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 26px 28px;
  margin: 0;
  padding-top: 26px;
  border-top: 1px solid rgba(127, 179, 162, 0.34);
}
.page-about .about-stat {
  min-width: 0;
}
.page-about .about-stat dt {
  margin: 0 0 8px;
  font-family: var(--font-num);
  font-size: 12px;
  letter-spacing: 0.1em;
  color: var(--pitch-moss);
}
.page-about .about-stat__num {
  margin: 0;
  font-family: var(--font-num);
  font-size: clamp(1.7rem, 4.4vw, 2.6rem);
  line-height: 1;
  font-weight: 500;
  color: var(--chalk);
}
.page-about .about-stat--signal .about-stat__num {
  color: var(--sig);
}
.page-about .about-stat__unit {
  margin-left: 5px;
  font-size: 0.4em;
  letter-spacing: 0.06em;
  color: var(--pitch-moss);
}

/* ---------- 主体框架 ---------- */
.page-about .about-shell {
  max-width: var(--content);
  margin-inline: auto;
  padding-inline: var(--pad);
  padding-block: clamp(36px, 6vw, 80px) clamp(48px, 8vw, 96px);
}

.page-about .index-rail {
  display: none;
}

@media (min-width: 960px) {
  .page-about .about-shell {
    display: grid;
    grid-template-columns: 72px minmax(0, 1fr);
    gap: 48px;
    align-items: start;
  }
  .page-about .index-rail {
    display: flex;
    flex-direction: column;
    gap: 16px;
    position: sticky;
    top: 96px;
    align-self: start;
    padding: 6px 0 6px 12px;
    border-left: 1px solid var(--ice-grid);
  }
}

.page-about .index-rail__item {
  display: flex;
  flex-direction: column;
  gap: 2px;
  margin-left: -13px;
  padding: 2px 0 2px 13px;
  border-left: 2px solid transparent;
  text-decoration: none;
  color: var(--graphite);
  transition: color 180ms ease, border-color 180ms ease;
}
.page-about .index-rail__item:hover {
  color: var(--ice-deep);
}
.page-about .index-rail__item.is-active {
  color: var(--ice);
  border-left-color: var(--ice);
}
.page-about .index-rail__no {
  font-family: var(--font-num);
  font-size: 11px;
  letter-spacing: 0.14em;
}
.page-about .index-rail__name {
  font-size: 13px;
  letter-spacing: 0.02em;
}

/* ---------- 章节通用 ---------- */
.page-about .about-sec {
  padding-block: clamp(34px, 5vw, 64px);
  border-top: 1px solid var(--ice-grid);
}
.page-about .about-sec:first-child {
  padding-top: 0;
  border-top: 0;
}
.page-about .sec__head {
  max-width: 62ch;
  margin-bottom: clamp(22px, 3.4vw, 40px);
}
.page-about .sec__num {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 0 0 10px;
  font-family: var(--font-num);
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--ice);
}
.page-about .sec__num::after {
  content: "";
  width: 34px;
  height: 1px;
  background: var(--ice);
}
.page-about .sec__title {
  margin: 0 0 10px;
  font-family: var(--font-head);
  font-size: clamp(1.6rem, 3.6vw, 2.3rem);
  line-height: 1.12;
  letter-spacing: -0.01em;
  color: var(--pitch);
}
.page-about .sec__lead {
  margin: 0;
  font-size: 0.94rem;
  line-height: 1.8;
  color: var(--graphite);
}

.page-about .prose p {
  max-width: 62ch;
  margin: 0 0 1.1em;
  font-size: 0.98rem;
  line-height: 1.85;
  color: var(--ink);
}
.page-about .prose p:last-child {
  margin-bottom: 0;
}
.page-about .annot--indent {
  max-width: 58ch;
  padding-left: 14px;
  border-left: 2px solid var(--ice-grid);
  font-size: 12px;
  line-height: 1.7;
  letter-spacing: 0.08em;
  color: var(--graphite);
}

/* ---------- 01 图文并置 ---------- */
.page-about .about-sec__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 28px;
}
@media (min-width: 860px) {
  .page-about .about-sec__grid {
    grid-template-columns: minmax(0, 1.12fr) minmax(0, 1fr);
    gap: 48px;
    align-items: start;
  }
  .page-about .about-sec__grid--team {
    grid-template-columns: minmax(0, 1fr) minmax(0, 0.92fr);
  }
}

.page-about .figure {
  margin: 0;
}
.page-about .figure__media {
  position: relative;
  overflow: hidden;
  background-color: var(--ice-grid);
  background-image: repeating-linear-gradient(45deg, rgba(255, 255, 255, 0.5) 0 1px, transparent 1px 9px);
  clip-path: polygon(0 0, calc(100% - 26px) 0, 100% 26px, 100% 100%, 0 100%);
}
.page-about .figure__media img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  filter: saturate(0.55) contrast(1.03);
}
.page-about .figure__cap {
  margin-top: 10px;
  font-family: var(--font-num);
  font-size: 12px;
  letter-spacing: 0.06em;
  line-height: 1.7;
  color: var(--graphite);
}
.page-about .figure--wide {
  margin-top: clamp(26px, 4vw, 44px);
}

/* ---------- 02 原则 ---------- */
.page-about .principles {
  list-style: none;
  margin: 0 0 clamp(30px, 4vw, 46px);
  padding: 0;
  border-top: 1px solid var(--ice-grid);
}
.page-about .principles__item {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 8px;
  padding: 20px 0;
  border-bottom: 1px dashed var(--ice-grid);
}
@media (min-width: 780px) {
  .page-about .principles__item {
    grid-template-columns: 96px minmax(0, 220px) minmax(0, 1fr);
    gap: 28px;
    align-items: baseline;
  }
}
.page-about .principles__idx {
  margin: 0;
  font-family: var(--font-num);
  font-size: 12px;
  letter-spacing: 0.12em;
  color: var(--ice-deep);
}
.page-about .principles__title {
  margin: 0;
  font-family: var(--font-head);
  font-size: 1.16rem;
  line-height: 1.3;
  color: var(--pitch);
}
.page-about .principles__item p:last-child {
  max-width: 62ch;
  margin: 0;
  font-size: 0.94rem;
  line-height: 1.85;
  color: var(--ink);
}

.page-about .compare {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  background-color: var(--ice-grid);
  border: 1px solid var(--ice-grid);
}
@media (min-width: 720px) {
  .page-about .compare {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}
.page-about .compare__col {
  background-color: var(--chalk);
  padding: 24px 22px;
  transition: background-color 200ms ease;
}
.page-about .compare__col:hover {
  background-color: var(--sig-pale);
}
.page-about .compare__col--alt:hover {
  background-color: #DCF0F8;
}
.page-about .compare__title {
  display: flex;
  align-items: baseline;
  gap: 4px;
  margin: 0 0 10px;
  font-family: var(--font-head);
  font-size: 1.1rem;
  color: var(--pitch);
}
.page-about .compare__title::after {
  content: ";";
  font-family: var(--font-num);
  color: var(--sig-deep);
}
.page-about .compare__body {
  max-width: 44ch;
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.85;
  color: var(--ink);
}

/* ---------- 03 三条线 ---------- */
.page-about .lanes {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 14px;
}
.page-about .lanes__item {
  padding: 20px 22px;
  background-color: var(--pitch-panel);
  color: var(--chalk);
  clip-path: polygon(0 0, calc(100% - 20px) 0, 100% 20px, 100% 100%, 0 100%);
}
.page-about .lanes__name {
  margin: 0 0 8px;
  font-family: var(--font-num);
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--sig);
}
.page-about .lanes__title {
  margin: 0 0 6px;
  font-family: var(--font-head);
  font-size: 1.14rem;
  color: var(--chalk);
}
.page-about .lanes__desc {
  margin: 0;
  font-size: 0.9rem;
  line-height: 1.75;
  color: var(--pitch-moss);
}

/* ---------- 04 时间轴 ---------- */
.page-about .timeline-wrap {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 34px;
}
@media (min-width: 960px) {
  .page-about .timeline-wrap {
    grid-template-columns: minmax(0, 1fr) minmax(0, 300px);
    gap: 56px;
    align-items: start;
  }
}
.page-about .timeline-figure {
  position: relative;
  z-index: 0;
}
.page-about .timeline {
  list-style: none;
  margin: 0;
  padding: 0;
}
.page-about .timeline__item {
  position: relative;
  padding-left: 30px;
  padding-bottom: 16px;
}
.page-about .timeline__item::before {
  content: "";
  position: absolute;
  left: 5px;
  top: 8px;
  width: 9px;
  height: 9px;
  background-color: var(--ice);
  transform: rotate(45deg);
}
.page-about .timeline__item::after {
  content: "";
  position: absolute;
  left: 9px;
  top: 22px;
  bottom: 0;
  border-left: 1px dashed var(--ice-grid);
}
.page-about .timeline__item:last-child {
  padding-bottom: 0;
}
.page-about .timeline__item:last-child::after {
  display: none;
}
.page-about .timeline__node {
  background-color: var(--chalk);
  border: 1px solid var(--ice-grid);
  transition: border-color 200ms ease;
}
.page-about .timeline__node:hover,
.page-about .timeline__node[open] {
  border-color: var(--ice);
}
.page-about .timeline__summary {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 10px;
  padding: 13px 16px;
  cursor: pointer;
  list-style: none;
}
.page-about .timeline__summary::-webkit-details-marker {
  display: none;
}
.page-about .timeline__summary::marker {
  content: "";
}
.page-about .timeline__season {
  flex: 0 0 auto;
  font-family: var(--font-num);
  font-size: 12px;
  letter-spacing: 0.1em;
  color: var(--ice-deep);
}
.page-about .timeline__label {
  flex: 1 1 60%;
  font-family: var(--font-head);
  font-size: 1.04rem;
  line-height: 1.35;
  color: var(--pitch);
}
.page-about .timeline__summary::after {
  content: "+";
  flex: 0 0 auto;
  font-family: var(--font-num);
  font-size: 1rem;
  color: var(--ice);
}
.page-about .timeline__node[open] .timeline__summary::after {
  content: "–";
}
.page-about .timeline__body {
  padding: 0 16px 14px;
  border-top: 1px dashed var(--ice-grid);
}
.page-about .timeline__body p {
  max-width: 62ch;
  margin: 12px 0 0;
  font-size: 0.9rem;
  line-height: 1.8;
  color: var(--graphite);
}

/* ---------- 05 版本沿革 ---------- */
.page-about .versions {
  margin-bottom: clamp(26px, 4vw, 44px);
}
.page-about .versions__bar {
  height: 4px;
  margin-bottom: 20px;
  background: linear-gradient(90deg, var(--ice-grid) 0%, var(--ice) 58%, var(--sig) 100%);
}
.page-about .versions__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 22px;
}
@media (min-width: 720px) {
  .page-about .versions__list {
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 24px;
  }
}
.page-about .versions__mark {
  position: relative;
  padding-top: 18px;
  border-top: 1px solid var(--ice-grid);
}
.page-about .versions__dot {
  position: absolute;
  top: -7px;
  left: 0;
  width: 10px;
  height: 10px;
  background-color: var(--chalk);
  border: 2px solid var(--ice);
}
.page-about .versions__mark:last-child .versions__dot {
  background-color: var(--sig);
  border-color: var(--sig);
}
.page-about .versions__num {
  display: block;
  font-family: var(--font-num);
  font-size: 1.3rem;
  line-height: 1.2;
  color: var(--pitch);
}
.page-about .versions__name {
  display: block;
  margin-top: 4px;
  font-family: var(--font-head);
  font-size: 1.02rem;
  color: var(--ice-deep);
}
.page-about .versions__note {
  display: block;
  margin-top: 6px;
  font-size: 0.84rem;
  line-height: 1.7;
  color: var(--graphite);
}
.page-about .versions__delta {
  display: block;
  margin-top: 8px;
  padding-left: 10px;
  border-left: 2px solid var(--ice-grid);
  font-size: 0.78rem;
  line-height: 1.7;
  color: var(--graphite);
  transition: color 200ms ease, border-color 200ms ease;
}
.page-about .versions__mark:hover .versions__delta,
.page-about .versions__mark:focus-within .versions__delta {
  color: var(--ice-deep);
  border-left-color: var(--sig);
}

/* ---------- 06 公开边界 ---------- */
.page-about .boundary {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  margin-bottom: 24px;
  background-color: var(--ice-grid);
  border: 1px solid var(--ice-grid);
}
@media (min-width: 720px) {
  .page-about .boundary {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}
.page-about .boundary__col {
  padding: 24px 22px;
  background-color: var(--chalk);
}
.page-about .boundary__col--off {
  background-color: var(--ice-bg);
}
.page-about .boundary__head {
  margin: 0 0 14px;
  font-family: var(--font-head);
  font-size: 1.06rem;
  color: var(--pitch);
}
.page-about .boundary__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 10px;
}
.page-about .boundary__list li {
  position: relative;
  padding-left: 16px;
  font-size: 0.9rem;
  line-height: 1.75;
  color: var(--ink);
}
.page-about .boundary__list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.66em;
  width: 7px;
  height: 1px;
  background-color: var(--ice);
}
.page-about .boundary__note {
  padding-left: 16px;
  border-left: 2px solid var(--sig);
}
.page-about .boundary__note p {
  max-width: 62ch;
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.85;
  color: var(--graphite);
}
.page-about .boundary__note a {
  color: var(--sig-deep);
  text-decoration: underline;
  text-underline-offset: 3px;
}

/* ---------- 页尾入口 ---------- */
.page-about .about-links {
  padding-top: 32px;
  border-top: 1px solid var(--ice-grid);
}
.page-about .about-links__title {
  margin: 0 0 16px;
  font-family: var(--font-head);
  font-size: 1.2rem;
  color: var(--pitch);
}
.page-about .about-links__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
}
@media (min-width: 720px) {
  .page-about .about-links__list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    column-gap: 40px;
  }
}
.page-about .about-links__list a {
  display: block;
  padding: 12px 0;
  border-bottom: 1px dashed var(--ice-grid);
  font-size: 0.92rem;
  line-height: 1.6;
  color: var(--ice-deep);
  text-decoration: none;
  transition: color 180ms ease, padding-left 180ms ease;
}
.page-about .about-links__list a:hover {
  padding-left: 8px;
  color: var(--sig-deep);
}

/* ---------- 焦点与动效收敛 ---------- */
.page-about :focus-visible {
  outline: 2px solid var(--ice);
  outline-offset: 2px;
}
@media (prefers-reduced-motion: reduce) {
  .page-about *,
  .page-about *::before,
  .page-about *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}
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