.page-about {
  background: var(--ink-900);
  color: var(--text-dark);
  font-family: var(--font-body);
  overflow-x: hidden;
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  padding: calc(var(--header-h) + clamp(28px, 6vw, 72px)) 0 clamp(30px, 5vw, 56px);
  background:
    radial-gradient(120% 90% at 88% 6%, rgba(37, 230, 200, .14), transparent 58%),
    radial-gradient(100% 80% at 0% 100%, rgba(255, 106, 43, .12), transparent 62%),
    var(--ink-900);
  border-bottom: 1px solid var(--hairline);
}

.page-about .about-crumbs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  margin: 0 0 clamp(20px, 4vw, 40px);
  padding: 0;
  list-style: none;
  font-size: 12.5px;
  letter-spacing: .06em;
  color: var(--silver);
}

.page-about .about-crumbs .breadcrumbs__item + .breadcrumbs__item::before {
  content: "/";
  margin-right: 8px;
  color: var(--hairline);
}

.page-about .about-crumbs .breadcrumbs__link {
  color: var(--silver);
  text-decoration: none;
}

.page-about .about-crumbs .breadcrumbs__link:hover {
  color: var(--cyan);
}

.page-about .about-crumbs .breadcrumbs__current {
  color: var(--paper);
}

.page-about .about-hero__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(24px, 4vw, 48px);
}

.page-about .about-hero__eyebrow {
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .22em;
  text-transform: uppercase;
  color: var(--cyan);
}

.page-about .about-hero__title {
  margin: 0 0 18px;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(32px, 6.4vw, 64px);
  line-height: 1.06;
  letter-spacing: -.02em;
  color: var(--paper-hi);
}

.page-about .about-hero__lede {
  margin: 0;
  max-width: 46ch;
  font-size: clamp(15px, 1.7vw, 17px);
  line-height: 1.8;
  color: var(--silver);
}

.page-about .about-hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: clamp(22px, 3.5vw, 34px);
}

.page-about .about-index {
  border-top: 1px solid var(--hairline);
}

.page-about .about-index__item {
  display: grid;
  grid-template-columns: 38px minmax(0, 1fr) auto;
  gap: 12px;
  align-items: baseline;
  padding: 13px 0;
  border-bottom: 1px solid var(--hairline);
  color: var(--text-dark);
  text-decoration: none;
  transition: color var(--t-fast) var(--ease), padding-left var(--t-fast) var(--ease);
}

.page-about .about-index__item:hover,
.page-about .about-index__item:focus-visible {
  color: var(--cyan);
  padding-left: 6px;
}

.page-about .about-index__num {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--orange);
}

.page-about .about-index__label {
  font-size: 14.5px;
  line-height: 1.5;
}

.page-about .about-index__arrow {
  font-size: 13px;
  color: var(--silver);
}

.page-about .about-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin-top: clamp(28px, 5vw, 52px);
  background: var(--hairline);
  border: 1px solid var(--hairline);
}

.page-about .about-stats__cell {
  background: var(--ink-800);
  padding: 16px 14px;
}

.page-about .about-stats__cell .stat__value {
  display: block;
  font-family: var(--font-mono);
  font-size: clamp(19px, 2.4vw, 27px);
  line-height: 1.2;
  color: var(--cyan);
}

.page-about .about-stats__cell .stat__label {
  display: block;
  margin-top: 8px;
  font-size: 12.5px;
  letter-spacing: .05em;
  color: var(--silver);
}

/* ---------- 章节跳转条 ---------- */
.page-about .about-chapnav {
  position: sticky;
  top: var(--header-h);
  z-index: 6;
  background: rgba(10, 17, 34, .94);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--hairline);
}

.page-about .about-chapnav__list {
  display: flex;
  gap: 22px;
  margin: 0;
  padding: 13px 0;
  list-style: none;
  overflow-x: auto;
  white-space: nowrap;
  scrollbar-width: none;
}

.page-about .about-chapnav__list::-webkit-scrollbar {
  display: none;
}

.page-about .about-chapnav__link {
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: .06em;
  color: var(--silver);
  text-decoration: none;
  padding-bottom: 3px;
  border-bottom: 1px solid transparent;
  transition: color var(--t-fast) var(--ease), border-color var(--t-fast) var(--ease);
}

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

/* ---------- 章节骨架 ---------- */
.page-about .about-section {
  padding: clamp(42px, 7vw, 92px) 0;
  border-bottom: 1px solid var(--hairline);
}

.page-about .about-section--last {
  border-bottom: 0;
  padding-bottom: clamp(56px, 9vw, 120px);
}

.page-about .chapter-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(16px, 3vw, 36px);
}

.page-about .chapter-rail {
  display: flex;
  flex-direction: row;
  align-items: baseline;
  gap: 16px;
}

.page-about .chapter-rail .chapter__num {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(46px, 8vw, 96px);
  line-height: .88;
  letter-spacing: -.03em;
  color: transparent;
  -webkit-text-stroke: 1.4px var(--orange);
}

.page-about .chapter-rail .annotation--vertical {
  writing-mode: vertical-rl;
  text-orientation: mixed;
  font-size: 11.5px;
  letter-spacing: .3em;
  text-transform: uppercase;
  color: var(--silver);
}

.page-about .about-ch__title {
  margin: 0 0 clamp(16px, 2.4vw, 26px);
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(22px, 3.2vw, 36px);
  line-height: 1.18;
  letter-spacing: -.01em;
  color: var(--paper-hi);
}

.page-about .about-intro,
.page-about .about-note {
  margin: 0 0 clamp(16px, 2.4vw, 24px);
  max-width: 62ch;
  font-size: clamp(14.5px, 1.6vw, 16.5px);
  line-height: 1.8;
  color: var(--silver);
}

.page-about .about-note {
  margin-top: clamp(20px, 3vw, 30px);
  padding-left: 16px;
  border-left: 2px solid var(--cyan);
  color: var(--text-dark);
}

.page-about .chapter-body .prose p {
  margin: 0 0 1.05em;
  max-width: 66ch;
  font-size: clamp(15px, 1.7vw, 17px);
  line-height: 1.85;
  color: var(--text-dark);
}

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

/* ---------- 章节 02 的问题清单 ---------- */
.page-about .fix-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(22px, 3.5vw, 40px);
  align-items: start;
}

.page-about .fix-list {
  border-top: 1px solid var(--hairline);
}

.page-about .fix-item {
  padding: 18px 0 20px;
  border-bottom: 1px solid var(--hairline);
}

.page-about .fix-item__q {
  margin: 0 0 8px;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(16px, 1.9vw, 19px);
  line-height: 1.5;
  color: var(--paper);
}

.page-about .fix-item__q::before {
  content: "";
  display: inline-block;
  width: 8px;
  height: 8px;
  margin-right: 10px;
  background: var(--orange);
  vertical-align: 2px;
}

.page-about .fix-item__a {
  margin: 0;
  max-width: 60ch;
  font-size: clamp(14px, 1.6vw, 16px);
  line-height: 1.8;
  color: var(--silver);
}

/* ---------- 图片 ---------- */
.page-about .about-figure {
  margin: 0 0 clamp(22px, 3vw, 34px);
}

.page-about .about-figure--wide {
  margin-bottom: clamp(28px, 4vw, 48px);
}

.page-about .about-figure--break {
  margin: clamp(30px, 5vw, 56px) 0 0;
}

.page-about .media-frame {
  overflow: hidden;
  border: 1px solid var(--hairline);
  background: var(--ink-800);
}

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

.page-about .media-frame__caption {
  display: block;
  margin-top: 10px;
  font-size: 12.5px;
  line-height: 1.6;
  letter-spacing: .04em;
  color: var(--silver);
}

/* ---------- 章节 03 版本演进 ---------- */
.page-about .verlist {
  position: relative;
  margin-top: clamp(18px, 3vw, 28px);
  padding-left: 26px;
}

.page-about .verlist::before {
  content: "";
  position: absolute;
  left: 5px;
  top: 8px;
  bottom: 8px;
  width: 1px;
  background: var(--hairline);
}

.page-about .verlist__item {
  position: relative;
  border-bottom: 1px solid var(--hairline);
}

.page-about .verlist__item:first-child {
  border-top: 1px solid var(--hairline);
}

.page-about .verlist__node {
  position: absolute;
  left: -26px;
  top: 20px;
  width: 11px;
  height: 11px;
  background: var(--ink-900);
  border: 1px solid var(--orange);
}

.page-about .verlist__item[data-open="true"] .verlist__node,
.page-about .verlist__trigger[aria-expanded="true"] .verlist__node {
  background: var(--orange);
}

.page-about .verlist__trigger {
  display: flex;
  align-items: center;
  gap: 14px;
  width: 100%;
  padding: 17px 0;
  border: 0;
  background: none;
  text-align: left;
  cursor: pointer;
  color: inherit;
  font: inherit;
}

.page-about .verlist__idx {
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: .1em;
  color: var(--cyan);
}

.page-about .verlist__title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(15px, 1.8vw, 18px);
  line-height: 1.5;
  color: var(--paper);
  transition: color var(--t-fast) var(--ease);
}

.page-about .verlist__trigger:hover .verlist__title,
.page-about .verlist__trigger:focus-visible .verlist__title {
  color: var(--orange);
}

.page-about .verlist__icon {
  position: relative;
  flex: 0 0 14px;
  width: 14px;
  height: 14px;
  margin-left: auto;
}

.page-about .verlist__icon::before,
.page-about .verlist__icon::after {
  content: "";
  position: absolute;
  left: 0;
  top: 6px;
  width: 14px;
  height: 1px;
  background: var(--silver);
  transition: transform var(--t-mid) var(--ease), background var(--t-fast) var(--ease);
}

.page-about .verlist__icon::after {
  transform: rotate(90deg);
}

.page-about .verlist__trigger[aria-expanded="true"] .verlist__icon::after {
  transform: rotate(90deg) scaleX(0);
}

.page-about .verlist__trigger[aria-expanded="true"] .verlist__icon::before {
  background: var(--orange);
}

.page-about .verlist .accordion__panel {
  padding: 0 0 4px;
}

.page-about .verlist .accordion__body {
  padding: 0 0 20px;
}

.page-about .verlist .accordion__body p {
  margin: 0;
  max-width: 62ch;
  font-size: clamp(14px, 1.6vw, 16px);
  line-height: 1.85;
  color: var(--silver);
}

/* ---------- 章节 04 流程 ---------- */
.page-about .flow {
  margin-top: clamp(22px, 3vw, 32px);
}

.page-about .flow__step {
  display: grid;
  grid-template-columns: 88px minmax(0, 1fr);
  gap: 14px;
  padding: 16px 0;
  border-top: 1px solid var(--hairline);
}

.page-about .flow__step:last-of-type {
  border-bottom: 1px solid var(--hairline);
}

.page-about .flow__idx {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: .12em;
  color: var(--orange);
}

.page-about .flow__name {
  margin: 0 0 6px;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 15.5px;
  color: var(--paper);
}

.page-about .flow__desc {
  margin: 0;
  max-width: 58ch;
  font-size: clamp(13.5px, 1.55vw, 15.5px);
  line-height: 1.8;
  color: var(--silver);
}

.page-about .flow__arrow {
  display: block;
  width: 0;
  height: 0;
  margin: 6px 0 6px 34px;
  border-left: 5px solid transparent;
  border-right: 5px solid transparent;
  border-top: 7px solid var(--magenta);
}

/* ---------- 章节 06 联系 ---------- */
.page-about .contact-lines {
  margin-top: clamp(20px, 3vw, 30px);
  border-top: 1px solid var(--hairline);
}

.page-about .contact-lines .contact-line {
  display: grid;
  grid-template-columns: 1fr;
  gap: 6px;
  padding: 15px 0;
  border-bottom: 1px solid var(--hairline);
}

.page-about .contact-lines .contact-line__key {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: .16em;
  color: var(--silver);
}

.page-about .contact-lines .contact-line__value {
  font-size: clamp(14px, 1.6vw, 16px);
  line-height: 1.6;
  color: var(--paper-hi);
  word-break: break-word;
}

.page-about .copy-btn {
  justify-self: start;
  padding: 7px 14px;
  border: 1px solid var(--hairline);
  border-radius: 0;
  background: transparent;
  color: var(--silver);
  font-family: var(--font-body);
  font-size: 12.5px;
  letter-spacing: .08em;
  cursor: pointer;
  transition: background var(--t-fast) var(--ease), color var(--t-fast) var(--ease), border-color var(--t-fast) var(--ease);
}

.page-about .copy-btn:hover,
.page-about .copy-btn:focus-visible {
  border-color: var(--cyan);
  color: var(--cyan);
}

.page-about .copy-btn.is-copied {
  background: var(--cyan);
  border-color: var(--cyan);
  color: var(--ink-900);
}

.page-about .about-cta {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: clamp(24px, 3.5vw, 36px);
}

/* ---------- 宽屏布局 ---------- */
@media (min-width: 720px) {
  .page-about .about-stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .contact-lines .contact-line {
    grid-template-columns: 104px minmax(0, 1fr) auto;
    gap: 16px;
    align-items: center;
  }

  .page-about .copy-btn {
    justify-self: end;
  }
}

@media (min-width: 980px) {
  .page-about .about-hero__grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
    gap: clamp(32px, 4vw, 64px);
    align-items: start;
  }

  .page-about .fix-grid {
    grid-template-columns: minmax(0, 1.35fr) minmax(0, .65fr);
  }

  .page-about .chapter-rail {
    flex-direction: column;
    align-items: flex-start;
    gap: 18px;
  }
}

@media (min-width: 1040px) {
  .page-about .chapter-grid {
    grid-template-columns: 172px minmax(0, 1fr);
    gap: clamp(24px, 3vw, 48px);
  }

  .page-about .chapter-rail {
    position: sticky;
    top: calc(var(--header-h) + 82px);
    align-self: start;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-index__item,
  .page-about .verlist__icon::before,
  .page-about .verlist__icon::after,
  .page-about .copy-btn,
  .page-about .about-chapnav__link {
    transition: none;
  }
}
</main>