.page-about {
  --about-gap: 20px;
  --about-measure: 34em;
  background: var(--ink-900);
  color: var(--slate-100);
  font-family: var(--font-body);
  font-size: var(--fs-16);
  line-height: 1.8;
}

.page-about * {
  box-sizing: border-box;
}

.page-about .about-crumb {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 18px 20px 0;
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.04em;
  color: var(--slate-400);
}

.page-about .breadcrumb__sep {
  margin: 0 8px;
  color: var(--line-700);
}

/* ---------- 首屏框景 ---------- */

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

.page-about .about-hero__frame {
  position: relative;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 44px 20px 52px;
  border: 1px solid var(--line-700);
  background:
    radial-gradient(120% 130% at 0% 0%, rgba(22, 115, 255, 0.14), transparent 58%),
    var(--ink-950);
}

.page-about .about-hero__frame::before {
  content: "";
  position: absolute;
  top: 10px;
  left: 10px;
  width: 42px;
  height: 42px;
  border-top: 1px solid var(--mint-400);
  border-left: 1px solid var(--mint-400);
  pointer-events: none;
}

.page-about .about-hero__frame::after {
  content: "";
  position: absolute;
  left: 20px;
  right: 20px;
  bottom: 0;
  height: 7px;
  background-image: repeating-linear-gradient(90deg, var(--line-700) 0 1px, transparent 1px 34px);
  pointer-events: none;
}

.page-about .about-hero__code {
  display: inline-block;
  padding: 5px 12px;
  border: 1px solid var(--line-700);
  border-radius: 999px;
  background: rgba(10, 26, 47, 0.7);
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.14em;
  color: var(--mint-400);
}

.page-about .about-hero h1 {
  margin: 24px 0 0;
  max-width: 18em;
  font-family: var(--font-head);
  font-size: clamp(1.9rem, 6.4vw, 4rem);
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: -0.02em;
  color: var(--slate-100);
}

.page-about .about-hero__lede {
  max-width: var(--about-measure);
  margin: 22px 0 0;
  font-size: var(--fs-16);
  line-height: 1.85;
  color: var(--slate-400);
}

.page-about .about-hero__facts {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 10px 28px;
  margin: 30px 0 0;
  padding: 0;
}

.page-about .about-hero__facts li {
  display: flex;
  align-items: baseline;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.04em;
}

.page-about .about-hero__k {
  color: var(--slate-400);
}

.page-about .about-hero__v {
  color: var(--brand-300);
  font-weight: 700;
}

.page-about .about-hero__stamp {
  display: block;
  margin-top: 28px;
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.06em;
  color: var(--slate-400);
}

/* ---------- 双栏骨架 ---------- */

.page-about .about-layout {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 44px 20px 72px;
}

.page-about .about-layout > * {
  min-width: 0;
}

.page-about .about-rail {
  margin-bottom: 40px;
}

.page-about .about-rail__title {
  margin: 0 0 12px;
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.18em;
  color: var(--slate-400);
}

.page-about .about-rail__list {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 6px 8px;
  margin: 0;
  padding: 0;
}

.page-about .about-rail__link {
  display: inline-flex;
  align-items: baseline;
  gap: 8px;
  padding: 6px 10px;
  border-left: 2px solid transparent;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  background: rgba(18, 41, 74, 0.45);
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.03em;
  color: var(--slate-400);
  text-decoration: none;
  transition: color 160ms var(--ease), border-color 160ms var(--ease);
}

.page-about .about-rail__link:hover,
.page-about .about-rail__link:focus-visible {
  color: var(--slate-100);
}

.page-about .about-rail__link[aria-current="true"] {
  color: var(--mint-400);
  border-left-color: var(--mint-400);
}

.page-about .about-rail__idx {
  color: var(--brand-300);
  font-weight: 700;
}

/* ---------- 章节通用 ---------- */

.page-about .about-section + .about-section {
  margin-top: 60px;
}

.page-about .about-section .eyebrow {
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.18em;
  color: var(--brand-300);
}

.page-about .about-section h2 {
  margin: 0 0 20px;
  max-width: 20em;
  font-family: var(--font-head);
  font-size: clamp(1.4rem, 4.6vw, 2.05rem);
  font-weight: 700;
  line-height: 1.22;
  letter-spacing: -0.02em;
  color: var(--slate-100);
}

.page-about .about-section h3 {
  margin: 0 0 6px;
  font-family: var(--font-head);
  font-size: var(--fs-16);
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--slate-100);
}

.page-about .about-prose {
  max-width: var(--about-measure);
  font-size: var(--fs-16);
  line-height: 1.85;
  color: var(--slate-400);
}

.page-about .about-prose p {
  margin: 0 0 16px;
}

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

.page-about .about-subhead {
  margin: 40px 0 16px;
}

.page-about .about-inline-link {
  max-width: var(--about-measure);
  margin: 32px 0 0;
  font-size: var(--fs-14);
  line-height: 1.8;
  color: var(--slate-400);
}

/* ---------- 折叠与提示 ---------- */

.page-about .about-fold {
  max-width: var(--about-measure);
  margin-top: 24px;
  border: 1px solid var(--line-700);
  border-radius: var(--radius-sm);
  background: rgba(18, 41, 74, 0.4);
}

.page-about .about-fold > summary {
  position: relative;
  padding: 12px 44px 12px 16px;
  cursor: pointer;
  list-style: none;
  font-family: var(--font-mono);
  font-size: var(--fs-14);
  letter-spacing: 0.03em;
  color: var(--brand-300);
}

.page-about .about-fold > summary::-webkit-details-marker {
  display: none;
}

.page-about .about-fold > summary::after {
  content: "+";
  position: absolute;
  right: 16px;
  top: 50%;
  transform: translateY(-50%);
  font-family: var(--font-mono);
  font-size: var(--fs-18);
  color: var(--mint-400);
}

.page-about .about-fold[open] > summary::after {
  content: "−";
}

.page-about .about-fold__body {
  padding: 0 16px 14px;
  font-size: var(--fs-14);
  line-height: 1.85;
  color: var(--slate-400);
}

.page-about .about-fold__body p {
  margin: 0;
}

.page-about .about-note {
  max-width: var(--about-measure);
  margin-top: 24px;
}

/* ---------- 图片 ---------- */

.page-about .about-figure {
  margin: 26px 0 0;
  border: 1px solid var(--line-700);
  border-radius: var(--radius-md);
  overflow: hidden;
  background: var(--ink-950);
}

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

.page-about .about-figure figcaption {
  padding: 10px 14px;
  border-top: 1px solid var(--line-700);
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.03em;
  color: var(--slate-400);
}

/* ---------- 模块索引 ---------- */

.page-about .about-mods {
  list-style: none;
  display: grid;
  gap: 24px 32px;
  margin: 30px 0 0;
  padding: 0;
}

.page-about .about-mod {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  gap: 10px;
  align-items: start;
}

.page-about .about-mod__no {
  padding-top: 3px;
  font-family: var(--font-mono);
  font-size: var(--fs-14);
  font-weight: 700;
  letter-spacing: 0.06em;
  color: var(--brand-300);
}

.page-about .about-mod p {
  margin: 0;
  font-size: var(--fs-14);
  line-height: 1.8;
  color: var(--slate-400);
}

/* ---------- 三个动作 ---------- */

.page-about .about-actions {
  list-style: none;
  display: grid;
  gap: 40px;
  margin: 34px 0 0;
  padding: 0;
}

.page-about .about-action {
  display: grid;
  gap: 10px;
  align-items: start;
}

.page-about .about-action .step-index {
  display: block;
  font-family: var(--font-head);
  font-size: 68px;
  font-weight: 900;
  line-height: 0.86;
  letter-spacing: -0.04em;
  color: var(--brand-500);
}

.page-about .about-action__body {
  max-width: var(--about-measure);
}

.page-about .about-action__body p {
  margin: 0 0 10px;
  font-size: var(--fs-16);
  line-height: 1.8;
  color: var(--slate-400);
}

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

/* ---------- 分段切换 ---------- */

.page-about .about-seg {
  margin-top: 26px;
}

.page-about .about-seg__tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 18px;
}

.page-about .about-seg .segmented__btn {
  padding: 8px 14px;
  border: 1px solid var(--line-700);
  border-radius: var(--radius-sm);
  background: var(--ink-800);
  color: var(--slate-400);
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.04em;
  cursor: pointer;
  transition: color 160ms var(--ease), background 160ms var(--ease), border-color 160ms var(--ease);
}

.page-about .about-seg .segmented__btn:hover,
.page-about .about-seg .segmented__btn:focus-visible {
  color: var(--slate-100);
  border-color: var(--brand-300);
}

.page-about .about-seg .segmented__btn[aria-selected="true"] {
  background: var(--mint-400);
  border-color: var(--mint-400);
  color: var(--ink-950);
  font-weight: 700;
}

.page-about .about-seg .segmented__panel {
  padding: 18px 20px;
  border: 1px solid var(--line-700);
  border-radius: var(--radius-md);
  background: rgba(18, 41, 74, 0.55);
  backdrop-filter: blur(6px);
}

.page-about .about-sample {
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-size: var(--fs-14);
  letter-spacing: 0.02em;
  color: var(--mint-400);
  word-break: break-word;
}

.page-about .about-panel-text {
  margin: 0;
  max-width: var(--about-measure);
  font-size: var(--fs-14);
  line-height: 1.8;
  color: var(--slate-400);
}

/* ---------- 变更标签 ---------- */

.page-about .about-labels {
  list-style: none;
  display: grid;
  gap: 14px;
  margin: 0;
  padding: 0;
}

.page-about .about-label {
  border-left: 2px solid var(--line-700);
  padding-left: 12px;
}

.page-about .about-label[open] {
  border-left-color: var(--mint-400);
}

.page-about .about-label__chip {
  display: inline-flex;
  align-items: center;
  padding: 5px 14px;
  border: 1px solid var(--line-700);
  border-radius: 999px;
  background: var(--ink-800);
  color: var(--slate-100);
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.08em;
  cursor: pointer;
  list-style: none;
  transition: border-color 160ms var(--ease), color 160ms var(--ease);
}

.page-about .about-label__chip::-webkit-details-marker {
  display: none;
}

.page-about .about-label__chip:hover,
.page-about .about-label__chip:focus-visible {
  border-color: var(--mint-400);
  color: var(--mint-400);
}

.page-about .about-label__tip {
  margin: 10px 0 0;
  max-width: var(--about-measure);
  font-size: var(--fs-14);
  line-height: 1.8;
  color: var(--slate-400);
}

/* ---------- 分队与链路 ---------- */

.page-about .about-chain {
  list-style: none;
  display: grid;
  gap: 26px;
  margin: 30px 0 0;
  padding: 0;
}

.page-about .about-chain__item {
  display: grid;
  grid-template-columns: 36px minmax(0, 1fr);
  gap: 4px 12px;
  align-items: start;
}

.page-about .about-chain__no {
  grid-row: 1 / 3;
  padding-top: 2px;
  font-family: var(--font-mono);
  font-size: var(--fs-14);
  font-weight: 700;
  letter-spacing: 0.06em;
  color: var(--mint-400);
}

.page-about .about-chain__item h3 {
  grid-column: 2;
}

.page-about .about-chain__item p {
  grid-column: 2;
  margin: 0;
  max-width: var(--about-measure);
  font-size: var(--fs-14);
  line-height: 1.8;
  color: var(--slate-400);
}

.page-about .about-rhythm {
  max-width: var(--about-measure);
  margin-top: 34px;
  padding: 18px 20px;
  border: 1px solid var(--line-700);
  border-radius: var(--radius-md);
  background: rgba(18, 41, 74, 0.45);
  backdrop-filter: blur(6px);
}

.page-about .about-rhythm__label {
  margin: 0 0 12px;
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.18em;
  color: var(--brand-300);
}

.page-about .about-rhythm ul {
  list-style: none;
  display: grid;
  gap: 8px;
  margin: 0;
  padding: 0;
}

.page-about .about-rhythm li {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 16px;
  font-family: var(--font-mono);
  font-size: var(--fs-14);
  letter-spacing: 0.02em;
}

.page-about .about-rhythm__k {
  min-width: 5.5em;
  color: var(--slate-400);
}

.page-about .about-rhythm__v {
  color: var(--slate-100);
}

/* ---------- 加载慢双列 ---------- */

.page-about .about-latency {
  display: grid;
  gap: 30px;
}

.page-about .about-latency__text > .about-prose {
  margin-bottom: 4px;
}

.page-about .about-latency .about-chain {
  margin-top: 22px;
}

.page-about .about-figure--side {
  margin: 0;
  align-self: start;
}

/* ---------- 误解澄清 ---------- */

.page-about .about-myths {
  list-style: none;
  display: grid;
  gap: 22px;
  margin: 0;
  padding: 0;
}

.page-about .about-myth {
  max-width: var(--about-measure);
  padding-left: 16px;
  border-left: 2px solid var(--line-700);
}

.page-about .about-myth h3 {
  margin-bottom: 8px;
}

.page-about .about-myth p {
  margin: 0;
  font-size: var(--fs-14);
  line-height: 1.8;
  color: var(--slate-400);
}

/* ---------- 页尾元信息 ---------- */

.page-about .about-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 26px;
  margin-top: 64px;
  padding-top: 20px;
  border-top: 1px solid var(--line-700);
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.04em;
  color: var(--slate-400);
}

/* ---------- 断点 ---------- */

@media (min-width: 640px) {
  .page-about .about-crumb {
    padding-top: 24px;
  }

  .page-about .about-hero__frame {
    padding: 56px 36px 62px;
  }

  .page-about .about-layout {
    padding: 56px 24px 84px;
  }

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

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

  .page-about .about-chain {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 30px 32px;
  }

  .page-about .about-chain--team .about-chain__item {
    grid-template-columns: 36px minmax(0, 1fr);
  }
}

@media (min-width: 1024px) {
  .page-about .about-hero__frame {
    padding: 72px 48px 76px;
  }

  .page-about .about-layout {
    display: grid;
    grid-template-columns: minmax(196px, 23%) minmax(0, 1fr);
    gap: 56px;
    padding: 72px 24px 96px;
  }

  .page-about .about-rail {
    position: sticky;
    top: calc(var(--header-h) + 28px);
    align-self: start;
    margin-bottom: 0;
    padding-right: 8px;
    border-right: 1px solid var(--line-700);
  }

  .page-about .about-rail__list {
    flex-direction: column;
    flex-wrap: nowrap;
    gap: 2px;
  }

  .page-about .about-rail__link {
    width: 100%;
    background: transparent;
    padding: 7px 8px 7px 12px;
  }

  .page-about .about-section + .about-section {
    margin-top: 84px;
  }

  .page-about .about-action {
    grid-template-columns: 116px minmax(0, 1fr);
    gap: 26px;
  }

  .page-about .about-action .step-index {
    font-size: 96px;
  }

  .page-about .about-latency {
    grid-template-columns: minmax(0, 1.35fr) minmax(0, 1fr);
    gap: 46px;
    align-items: start;
  }

  .page-about .about-latency .about-chain {
    grid-template-columns: minmax(0, 1fr);
  }

  .page-about .about-figure--side {
    position: sticky;
    top: calc(var(--header-h) + 28px);
  }
}

@media (min-width: 1280px) {
  .page-about .about-action .step-index {
    font-size: 116px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-rail__link,
  .page-about .about-seg .segmented__btn,
  .page-about .about-label__chip {
    transition: none;
  }
}

@media (hover: none) {
  .page-about .about-rail__link:hover {
    color: var(--slate-400);
  }
}