.page-about {
  --story-rail: 176px;
  --story-top: 108px;
  background-color: var(--color-surface);
  color: var(--color-ink);
}

/* ===== 首屏：深墨章节预览台 ===== */
.page-about .story-hero {
  position: relative;
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  padding-block: calc(var(--space-8) * 2) var(--section-y);
  overflow: hidden;
}

.page-about .story-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: radial-gradient(circle at 1px 1px, var(--color-contrast-line) 1px, transparent 1.7px);
  background-size: 88px 88px;
  pointer-events: none;
}

.page-about .story-hero::after {
  content: "";
  position: absolute;
  inset-block: -20%;
  inset-inline-start: 58%;
  inset-inline-end: -14%;
  background: linear-gradient(118deg, transparent 0%, color-mix(in srgb, var(--color-contrast-accent) 20%, transparent) 48%, transparent 100%);
  transform: skewY(-4deg);
  pointer-events: none;
}

.page-about .story-hero__inner {
  position: relative;
  z-index: 1;
}

.page-about .story-hero__crumb {
  color: color-mix(in srgb, var(--color-contrast-ink) 62%, var(--color-contrast-surface));
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
}

.page-about .story-hero__crumb a {
  color: inherit;
  text-decoration: none;
}

.page-about .story-hero__crumb a:hover,
.page-about .story-hero__crumb a:focus-visible {
  color: var(--color-contrast-accent);
  text-decoration: underline;
  text-underline-offset: 4px;
}

.page-about .story-hero__eyebrow {
  margin-block-start: var(--space-6);
  color: var(--color-contrast-accent);
}

.page-about .story-hero__title {
  margin: var(--space-3) 0 0;
  font-family: var(--font-heading);
  font-size: clamp(var(--text-2xl), 4.6vw, var(--text-4xl));
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-contrast-ink);
  max-width: 22ch;
}

.page-about .story-hero__lede {
  margin: var(--space-3) 0 0;
  max-width: var(--measure);
  font-size: var(--text-lg);
  line-height: var(--leading-body);
  color: color-mix(in srgb, var(--color-contrast-ink) 84%, var(--color-contrast-surface));
}

.page-about .story-figures {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-4) var(--space-3);
  margin: var(--space-8) 0 0;
  padding-block-start: var(--space-4);
  border-block-start: var(--border-thin) solid var(--color-contrast-line);
}

.page-about .story-figures__cell {
  min-width: 0;
}

.page-about .story-figures__key {
  margin: 0 0 var(--space-1);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  color: color-mix(in srgb, var(--color-contrast-ink) 58%, var(--color-contrast-surface));
}

.page-about .story-figures__val {
  display: flex;
  align-items: baseline;
  gap: 2px;
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  line-height: 1;
  color: var(--color-contrast-accent);
}

.page-about .story-figures__unit {
  font-family: var(--font-body);
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
  color: color-mix(in srgb, var(--color-contrast-ink) 62%, var(--color-contrast-surface));
}

/* ===== 正文骨架 ===== */
.page-about .story-body {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  row-gap: var(--space-8);
  padding-block: var(--section-y);
  align-items: start;
}

.page-about .story-flow {
  min-width: 0;
}

/* ===== 跟随目录 ===== */
.page-about .story-toc {
  border-block-start: var(--border-thick) solid var(--color-primary);
  padding-block-start: var(--space-2);
}

.page-about .story-toc .toc-rail__title {
  margin: 0;
  font-size: var(--text-xs);
  letter-spacing: 0.22em;
  color: var(--color-ink-muted);
}

.page-about .story-toc__list {
  list-style: none;
  display: flex;
  gap: var(--space-3);
  margin: var(--space-2) 0 0;
  padding: 0;
  overflow-x: auto;
  scrollbar-width: none;
}

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

.page-about .story-toc__item {
  flex: 0 0 auto;
}

.page-about .story-toc__link {
  display: block;
  padding-block: var(--space-1);
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
  white-space: nowrap;
  text-decoration: none;
  color: var(--color-ink-muted);
  border-block-end: var(--border-thin) solid transparent;
}

.page-about .story-toc__link:hover,
.page-about .story-toc__link:focus-visible {
  color: var(--color-primary);
  border-block-end-color: var(--color-primary);
}

/* ===== 章节 ===== */
.page-about .story-chapter + .story-chapter {
  margin-block-start: var(--space-8);
  padding-block-start: var(--space-8);
  border-block-start: calc(var(--border-thin) * 3) double var(--color-line);
}

.page-about .story-chapter__index {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.16em;
  color: var(--color-ink-muted);
}

.page-about .story-chapter__num {
  font-size: var(--text-xl);
  font-weight: var(--weight-heading);
  letter-spacing: 0;
  color: var(--color-primary);
}

.page-about .story-chapter__title {
  margin: 0;
  max-width: 24ch;
  font-family: var(--font-heading);
  font-size: var(--text-3xl);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

.page-about .story-chapter__text {
  max-width: var(--measure);
  margin-block-start: var(--space-4);
}

.page-about .story-chapter__text--after {
  margin-block-start: var(--space-6);
}

.page-about .story-chapter__text p {
  margin: 0 0 var(--space-3);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink);
}

.page-about .story-chapter__text p:last-child {
  margin-block-end: 0;
}

.page-about .story-chapter__text a {
  color: var(--color-primary);
  text-decoration: none;
  border-block-end: var(--border-thin) solid var(--color-primary-soft);
}

.page-about .story-chapter__text a:hover,
.page-about .story-chapter__text a:focus-visible {
  border-block-end-color: var(--color-primary);
}

/* ===== 图片框 ===== */
.page-about .story-media {
  margin: var(--space-6) 0 0;
  border: 0;
  background: none;
  overflow: visible;
}

.page-about .story-media img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  border: var(--border-thin) solid var(--color-line);
}

.page-about .story-media__cap {
  margin-block-start: var(--space-2);
  font-size: var(--text-sm);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

/* ===== 三次扩张 ===== */
.page-about .story-stages {
  list-style: none;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-6);
  margin: var(--space-6) 0 0;
  padding: 0;
}

.page-about .story-stage {
  position: relative;
  padding-block-start: var(--space-3);
  border-block-start: var(--border-thick) solid var(--color-line);
}

.page-about .story-stage::before {
  content: "";
  position: absolute;
  inset-block-start: calc(var(--border-thick) * -1);
  inset-inline-start: 0;
  width: 36px;
  height: var(--border-thick);
  background-color: var(--color-primary);
}

.page-about .story-stage__kicker {
  margin: 0 0 var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  color: var(--color-accent);
}

.page-about .story-stage__title {
  margin: 0 0 var(--space-2);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  color: var(--color-ink);
}

.page-about .story-stage__body {
  margin: 0;
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

/* ===== 三种节奏 ===== */
.page-about .story-cycles {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-2);
  margin-block-start: var(--space-6);
}

.page-about .story-cycle {
  padding: var(--space-3);
  background-color: var(--color-surface-alt);
  border-inline-start: var(--border-thick) solid var(--color-accent);
}

.page-about .story-cycle__key {
  margin: 0 0 var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  color: var(--color-ink-muted);
}

.page-about .story-cycle__val {
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-2xl);
  line-height: 1.1;
  color: var(--color-primary);
}

.page-about .story-cycle__unit {
  margin-inline-start: 4px;
  font-family: var(--font-body);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}

.page-about .story-cycle__note {
  margin: 0;
  font-size: var(--text-sm);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

/* ===== 能力边界 ===== */
.page-about .story-boundary {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-4);
  margin-block-start: var(--space-4);
}

.page-about .story-boundary__col {
  padding: var(--space-3) var(--space-3) var(--space-4);
  border: var(--border-thin) solid var(--color-line);
}

.page-about .story-boundary__col--do {
  background-color: var(--color-highlight);
  border-block-start: var(--border-thick) solid var(--color-primary);
}

.page-about .story-boundary__col--dont {
  background-color: var(--color-surface-alt);
  border-block-start: var(--border-thick) solid var(--color-ink-muted);
}

.page-about .story-boundary__head {
  margin: 0 0 var(--space-3);
  font-family: var(--font-heading);
  font-size: var(--text-xl);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

.page-about .story-boundary__list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .story-boundary__list li {
  position: relative;
  margin-block-end: var(--space-2);
  padding-inline-start: var(--space-3);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink);
}

.page-about .story-boundary__list li:last-child {
  margin-block-end: 0;
}

.page-about .story-boundary__list li::before {
  content: "";
  position: absolute;
  inset-inline-start: 0;
  inset-block-start: 0.78em;
  width: 12px;
  height: var(--border-thick);
  background-color: var(--color-primary);
}

.page-about .story-boundary__col--dont .story-boundary__list li::before {
  background-color: var(--color-ink-muted);
}

/* ===== 下一步 ===== */
.page-about .story-next__list {
  list-style: none;
  margin: var(--space-4) 0 0;
  padding: 0;
  border-block-start: var(--border-thick) solid var(--color-ink);
}

.page-about .story-next__item {
  border-block-end: var(--border-thin) solid var(--color-line);
}

.page-about .story-next__link {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: var(--space-1) var(--space-3);
  padding: var(--space-3) var(--space-2);
  text-decoration: none;
  color: inherit;
}

.page-about .story-next__link:hover,
.page-about .story-next__link:focus-visible {
  background-color: var(--color-surface-alt);
}

.page-about .story-next__num {
  grid-column: 1;
  grid-row: 1;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.1em;
  color: var(--color-primary);
}

.page-about .story-next__title {
  grid-column: 2;
  grid-row: 1;
  font-family: var(--font-heading);
  font-size: var(--text-xl);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

.page-about .story-next__desc {
  grid-column: 2;
  grid-row: 2;
  font-size: var(--text-sm);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

/* ===== 响应式 ===== */
@media (min-width: 720px) {
  .page-about .story-figures {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .story-cycles {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

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

@media (min-width: 860px) {
  .page-about .story-stages {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: var(--space-4);
  }
}

@media (min-width: 1040px) {
  .page-about .story-body {
    grid-template-columns: var(--story-rail) minmax(0, 1fr);
    column-gap: var(--space-8);
  }

  .page-about .story-toc {
    position: sticky;
    top: var(--story-top);
  }

  .page-about .story-toc__list {
    flex-direction: column;
    gap: 0;
    overflow-x: visible;
    margin-block-start: var(--space-3);
  }

  .page-about .story-toc__item {
    border-block-end: var(--border-thin) solid var(--color-line);
  }

  .page-about .story-toc__item:last-child {
    border-block-end: 0;
  }

  .page-about .story-toc__link {
    white-space: normal;
    border-block-end: 0;
    padding-inline-start: var(--space-1);
    border-inline-start: var(--border-thin) solid transparent;
  }

  .page-about .story-toc__link:hover,
  .page-about .story-toc__link:focus-visible {
    border-inline-start-color: var(--color-primary);
    border-block-end-color: transparent;
    padding-inline-start: var(--space-2);
  }
}
</main>