.page-about {
  --about-cut: 18px;
  --about-rail-w: 236px;
  background: var(--paper);
  color: var(--ink);
}

.page-about .about-top {
  border-bottom: 1px solid var(--grid);
  background:
    radial-gradient(120% 90% at 88% 0%, rgba(169, 123, 51, 0.13), rgba(169, 123, 51, 0) 62%),
    var(--paper);
}

.page-about .about-crumb {
  padding: 18px 0 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--ink-soft);
}

.page-about .about-crumb a {
  color: var(--ink-soft);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color var(--speed) ease, border-color var(--speed) ease;
}

.page-about .about-crumb a:hover,
.page-about .about-crumb a:focus-visible {
  color: var(--vermilion);
  border-bottom-color: var(--vermilion);
}

.page-about .about-crumb__sep {
  margin: 0 8px;
  color: var(--copper);
}

.page-about .about-hero {
  display: grid;
  gap: 26px;
  padding: 22px 0 36px;
}

.page-about .about-hero__kicker {
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--vermilion-dark);
}

.page-about .about-hero__title {
  margin: 0 0 16px;
  font-family: var(--font-sans);
  font-weight: 900;
  font-size: 34px;
  line-height: 1.16;
  letter-spacing: -0.025em;
}

.page-about .about-hero__lede {
  margin: 0;
  max-width: 60ch;
  font-family: var(--font-serif);
  font-size: 16px;
  line-height: 1.85;
  color: var(--ink-soft);
}

.page-about .about-facts {
  margin: 0;
  padding: 18px 18px 8px;
  background: var(--paper-2);
  border-left: 3px solid var(--copper);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - var(--about-cut)), calc(100% - var(--about-cut)) 100%, 0 100%);
}

.page-about .about-facts__row {
  display: grid;
  grid-template-columns: 74px minmax(0, 1fr);
  gap: 10px;
  padding: 8px 0;
  border-bottom: 1px dotted var(--grid);
}

.page-about .about-facts__row:last-child {
  border-bottom: 0;
}

.page-about .about-facts dt {
  padding-top: 3px;
  font-family: var(--font-sans);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--copper);
}

.page-about .about-facts dd {
  margin: 0;
  font-family: var(--font-serif);
  font-size: 15px;
  line-height: 1.6;
  color: var(--ink);
}

/* ---------- 左右分屏骨架 ---------- */
.page-about .about-shell {
  display: grid;
  gap: 26px;
  padding: 26px 0 64px;
}

.page-about .about-rail,
.page-about .about-body {
  min-width: 0;
}

.page-about .about-rail__inner {
  background: var(--teal);
  color: var(--on-dark);
  padding: 20px 18px 22px;
  clip-path: polygon(
    0 0,
    calc(100% - var(--about-cut)) 0,
    100% var(--about-cut),
    100% 100%,
    var(--about-cut) 100%,
    0 calc(100% - var(--about-cut))
  );
}

.page-about .about-rail__mark {
  margin: 0 0 4px;
  font-family: var(--font-sans);
  font-weight: 800;
  font-size: 16px;
  letter-spacing: 0.02em;
  color: var(--on-dark);
}

.page-about .about-rail__sig {
  margin: 0 0 18px;
  font-family: var(--font-serif);
  font-size: 12px;
  line-height: 1.6;
  color: var(--on-dark-soft);
}

/* ---------- 左侧时间线 ---------- */
.page-about .about-years {
  display: flex;
  margin: 0 0 22px;
  padding: 0;
  list-style: none;
}

.page-about .about-years__item {
  position: relative;
  flex: 1 1 0;
  min-width: 0;
}

.page-about .about-years__link {
  display: flex;
  flex-direction: column;
  gap: 3px;
  padding: 6px 8px 6px 0;
  text-decoration: none;
  color: var(--on-dark);
}

.page-about .about-years__dot {
  display: block;
  width: 8px;
  height: 8px;
  margin-bottom: 6px;
  background: var(--copper);
  transform: rotate(45deg);
}

.page-about .about-years__year {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.04em;
  color: var(--copper-soft);
}

.page-about .about-years__label {
  font-family: var(--font-serif);
  font-size: 12px;
  line-height: 1.4;
  color: var(--on-dark-soft);
}

.page-about .about-years__link:hover .about-years__label,
.page-about .about-years__link:focus-visible .about-years__label {
  color: var(--on-dark);
}

/* ---------- 左侧章节索引 ---------- */
.page-about .about-nav__title {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  color: var(--copper-soft);
}

.page-about .about-nav__list {
  display: flex;
  margin: 0;
  padding: 0;
  list-style: none;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.page-about .about-nav__link {
  display: flex;
  gap: 8px;
  align-items: baseline;
  padding: 8px 12px;
  border-left: 1px solid rgba(233, 227, 214, 0.16);
  font-family: var(--font-sans);
  font-size: 13px;
  white-space: nowrap;
  text-decoration: none;
  color: var(--on-dark-soft);
  transition: color var(--speed) ease, background var(--speed) ease;
}

.page-about .about-nav__link:hover,
.page-about .about-nav__link:focus-visible {
  color: var(--on-dark);
  background: rgba(233, 227, 214, 0.06);
}

.page-about .about-nav__num {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--copper-soft);
}

.page-about .about-nav__link[aria-current="true"] {
  color: var(--on-dark);
  background: rgba(233, 227, 214, 0.08);
  box-shadow: inset 0 2px 0 var(--copper);
}

.page-about .about-nav__link[aria-current="true"] .about-nav__num {
  color: var(--copper-soft);
  font-weight: 700;
}

/* ---------- 章节 ---------- */
.page-about .chapter {
  padding: 32px 0 36px;
  border-bottom: 1px solid var(--grid);
  scroll-margin-top: 110px;
}

.page-about .chapter:first-child {
  padding-top: 4px;
}

.page-about .chapter:last-child {
  padding-bottom: 0;
  border-bottom: 0;
}

.page-about .chapter__head {
  display: flex;
  align-items: baseline;
  gap: 14px;
  margin-bottom: 16px;
}

.page-about .chapter__num {
  flex: 0 0 auto;
  margin: 0;
  font-family: var(--font-serif);
  font-style: italic;
  font-size: 20px;
  letter-spacing: 0.02em;
  color: var(--copper);
}

.page-about .chapter__title {
  margin: 0;
  font-family: var(--font-sans);
  font-weight: 800;
  font-size: 22px;
  line-height: 1.3;
  letter-spacing: -0.02em;
}

.page-about .copy {
  max-width: 70ch;
}

.page-about .copy p {
  margin: 0 0 1em;
  font-family: var(--font-serif);
  font-size: 16px;
  line-height: 1.85;
}

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

.page-about .chapter__body--with-figure {
  display: grid;
  gap: 22px;
}

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

.page-about .about-figure--flow {
  margin-top: 24px;
}

.page-about .about-banner {
  margin: 22px 0 0;
}

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

.page-about .media-frame__caption {
  margin-top: 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  line-height: 1.6;
  letter-spacing: 0.04em;
  color: var(--ink-soft);
}

/* ---------- 字段清单 ---------- */
.page-about .field-list {
  margin: 22px 0 0;
  padding: 0;
  display: grid;
  border-top: 1px solid var(--grid);
}

.page-about .field-list__row {
  display: grid;
  grid-template-columns: 84px minmax(0, 1fr);
  gap: 12px;
  padding: 12px 0;
  border-bottom: 1px solid var(--grid);
}

.page-about .field-list dt {
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 14px;
  color: var(--ink);
}

.page-about .field-list dd {
  margin: 0;
  font-family: var(--font-serif);
  font-size: 15px;
  line-height: 1.72;
  color: var(--ink-soft);
}

.page-about .field-list + .copy {
  margin-top: 20px;
}

/* ---------- 引用块 ---------- */
.page-about .quote {
  margin: 26px 0 0;
  padding: 20px 22px;
  background: var(--wine);
  color: var(--on-dark);
  clip-path: polygon(
    0 0,
    calc(100% - var(--about-cut)) 0,
    100% var(--about-cut),
    100% 100%,
    var(--about-cut) 100%,
    0 calc(100% - var(--about-cut))
  );
}

.page-about .quote p {
  margin: 0;
  font-family: var(--font-serif);
  font-size: 16px;
  line-height: 1.8;
}

.page-about .quote__by {
  display: block;
  margin-top: 12px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--copper-soft);
}

/* ---------- 工序步骤 ---------- */
.page-about .steps {
  margin: 22px 0 0;
  padding: 0;
  list-style: none;
}

.page-about .step {
  position: relative;
  padding: 16px 0 18px 46px;
  border-top: 1px solid var(--grid);
}

.page-about .step:last-child {
  border-bottom: 1px solid var(--grid);
}

.page-about .step:not(:last-child)::after {
  content: "";
  position: absolute;
  left: 13px;
  top: 44px;
  bottom: 4px;
  width: 1px;
  background: var(--copper);
  opacity: 0.55;
  transform: rotate(6deg);
  transform-origin: top center;
}

.page-about .step__num {
  position: absolute;
  left: 0;
  top: 17px;
  display: grid;
  place-items: center;
  width: 28px;
  height: 28px;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--paper);
  background: var(--teal);
  clip-path: polygon(0 0, calc(100% - 8px) 0, 100% 8px, 100% 100%, 8px 100%, 0 calc(100% - 8px));
}

.page-about .step__title {
  margin: 0 0 6px;
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 16px;
  line-height: 1.4;
}

.page-about .step__text {
  margin: 0;
  max-width: 62ch;
  font-family: var(--font-serif);
  font-size: 15px;
  line-height: 1.78;
  color: var(--ink-soft);
}

.page-about .steps + .copy {
  margin-top: 22px;
}

/* ---------- 版本卡片 ---------- */
.page-about .versions {
  display: grid;
  gap: 16px;
  margin: 22px 0 0;
}

.page-about .version-card {
  position: relative;
  padding: 20px 18px;
  background: var(--paper-2);
  border-top: 3px solid var(--vc, var(--copper));
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - var(--about-cut)), calc(100% - var(--about-cut)) 100%, 0 100%);
  transition: background var(--speed) ease;
}

.page-about .version-card:hover,
.page-about .version-card:focus-within {
  background: #ffffff;
}

.page-about .version-card--a {
  --vc: var(--copper);
}

.page-about .version-card--b {
  --vc: var(--teal);
}

.page-about .version-card--c {
  --vc: var(--vermilion);
}

.page-about .version-card__tag {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--vc, var(--copper));
}

.page-about .version-card__title {
  margin: 0 0 10px;
  font-family: var(--font-sans);
  font-weight: 800;
  font-size: 19px;
  line-height: 1.35;
  letter-spacing: -0.01em;
}

.page-about .version-card__text {
  margin: 0;
  font-family: var(--font-serif);
  font-size: 14px;
  line-height: 1.78;
  color: var(--ink-soft);
}

.page-about .version-card__more {
  margin: 12px 0 0;
  padding-top: 10px;
  border-top: 1px dashed var(--grid);
  font-family: var(--font-mono);
  font-size: 11px;
  line-height: 1.7;
  color: var(--ink);
}

.page-about .versions + .copy {
  margin-top: 22px;
}

/* ---------- 季度回顾 ---------- */
.page-about .about-split {
  display: grid;
  gap: 20px;
}

/* ---------- 受理事项 ---------- */
.page-about .help-grid {
  display: grid;
  gap: 14px;
  margin: 22px 0 0;
}

.page-about .help-card {
  padding: 18px 18px 20px;
  background: var(--paper-2);
  border-left: 3px solid var(--vermilion);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 14px), calc(100% - 14px) 100%, 0 100%);
}

.page-about .help-card__tag {
  margin: 0 0 8px;
  font-family: var(--font-sans);
  font-weight: 800;
  font-size: 16px;
  letter-spacing: -0.01em;
}

.page-about .help-card__text {
  margin: 0;
  font-family: var(--font-serif);
  font-size: 15px;
  line-height: 1.75;
  color: var(--ink-soft);
}

.page-about .about-cta {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin: 24px 0 0;
}

.page-about .about-next {
  display: grid;
  gap: 0;
  margin-top: 28px;
  border-top: 1px solid var(--grid);
}

.page-about .about-next__item {
  display: grid;
  gap: 4px;
  padding: 14px 0;
  border-bottom: 1px solid var(--grid);
  text-decoration: none;
  transition: background var(--speed) ease;
}

.page-about .about-next__item:hover,
.page-about .about-next__item:focus-visible {
  background: rgba(169, 123, 51, 0.08);
}

.page-about .about-next__k {
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 15px;
  color: var(--ink);
}

.page-about .about-next__v {
  font-family: var(--font-serif);
  font-size: 14px;
  line-height: 1.6;
  color: var(--ink-soft);
}

/* ---------- 响应式 ---------- */
@media (min-width: 760px) {
  .page-about .about-hero__title {
    font-size: 48px;
  }

  .page-about .about-hero__lede {
    font-size: 17px;
  }

  .page-about .chapter__title {
    font-size: 34px;
  }

  .page-about .chapter__num {
    font-size: 24px;
  }

  .page-about .copy p {
    font-size: 17px;
  }

  .page-about .field-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    column-gap: 38px;
  }

  .page-about .help-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 18px;
  }
}

@media (min-width: 820px) {
  .page-about .versions {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 18px;
  }
}

@media (min-width: 900px) {
  .page-about .chapter__body--with-figure {
    grid-template-columns: minmax(0, 1.35fr) minmax(0, 1fr);
    gap: 36px;
    align-items: start;
  }

  .page-about .about-split {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 40px;
  }
}

@media (min-width: 1000px) {
  .page-about .about-shell {
    grid-template-columns: var(--about-rail-w) minmax(0, 1fr);
    gap: 52px;
    align-items: start;
    padding-top: 34px;
  }

  .page-about .rail-sticky {
    position: sticky;
    top: 98px;
  }

  .page-about .about-years {
    display: block;
    margin-bottom: 26px;
  }

  .page-about .about-years__item {
    padding-bottom: 22px;
  }

  .page-about .about-years__item:not(:last-child)::after {
    content: "";
    position: absolute;
    left: 3px;
    top: 20px;
    height: calc(100% - 8px);
    width: 1px;
    background: var(--copper);
    opacity: 0.5;
    transform: rotate(9deg);
    transform-origin: top center;
  }

  .page-about .about-years__link {
    padding: 0;
  }

  .page-about .about-nav__list {
    display: block;
    overflow: visible;
  }

  .page-about .about-nav__link {
    padding: 9px 4px 9px 10px;
    border-left: 0;
    border-top: 1px solid rgba(233, 227, 214, 0.16);
  }

  .page-about .about-next__item {
    grid-template-columns: 240px minmax(0, 1fr);
    align-items: baseline;
    gap: 20px;
  }
}

@media (min-width: 1200px) {
  .page-about .about-hero__title {
    font-size: 64px;
  }

  .page-about .about-hero {
    grid-template-columns: minmax(0, 1.5fr) minmax(280px, 0.85fr);
    gap: 48px;
    align-items: end;
    padding-bottom: 42px;
  }
}

@media (hover: hover) and (min-width: 820px) {
  .page-about .version-card__more {
    max-height: 0;
    padding-top: 0;
    border-top-color: transparent;
    opacity: 0;
    overflow: hidden;
    transition: max-height 0.3s ease, opacity 0.3s ease, padding 0.3s ease;
  }

  .page-about .version-card:hover .version-card__more,
  .page-about .version-card:focus-within .version-card__more {
    max-height: 12em;
    padding-top: 10px;
    border-top-color: var(--grid);
    opacity: 1;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about * {
    transition: none !important;
    animation: none !important;
  }
}