.page-about {
  --about-hair: 1px solid var(--ink-700);
  --about-side-w: 216px;
}

/* 首屏 */
.page-about .about-hero {
  padding-block: clamp(26px, 4.2vw, 54px) clamp(22px, 3.4vw, 42px);
  border-bottom: var(--about-hair);
}

.page-about .about-hero h1 {
  margin: 14px 0 0;
  max-width: 22ch;
  font-family: var(--font-head);
  font-weight: 300;
  font-size: clamp(30px, 5.4vw, 56px);
  line-height: 1.1;
  letter-spacing: -0.02em;
  color: var(--white-050);
}

.page-about .about-hero__lede {
  margin: clamp(16px, 2.2vw, 24px) 0 0;
  max-width: 60ch;
  font-size: var(--t-sm);
  line-height: 1.8;
  color: var(--slate-300);
}

.page-about .hero-figures {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: clamp(12px, 2.4vw, 32px);
  margin: clamp(24px, 3.6vw, 40px) 0 0;
  padding-top: clamp(16px, 2.2vw, 26px);
  border-top: var(--about-hair);
}

.page-about .hero-figure dt {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.08em;
  color: var(--cyan-200);
}

.page-about .hero-figure dd {
  margin: 8px 0 0;
  font-family: var(--font-mono);
  font-size: clamp(20px, 3.2vw, 30px);
  font-weight: 500;
  letter-spacing: -0.01em;
  color: var(--white-050);
}

/* 章节索引 */
.page-about .chapter-index {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  padding-block: clamp(16px, 2.4vw, 24px);
  border-bottom: var(--about-hair);
}

.page-about .chapter-index a {
  padding: 7px 14px;
  border: 1px solid var(--ink-700);
  border-radius: var(--pill);
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.04em;
  color: var(--slate-300);
  text-decoration: none;
  transition: color 0.18s var(--ease), background-color 0.18s var(--ease),
    border-color 0.18s var(--ease);
}

.page-about .chapter-index a:hover,
.page-about .chapter-index a:focus-visible {
  color: var(--ink-950);
  background: var(--cyan-400);
  border-color: var(--cyan-400);
}

.page-about .chapter-index a[aria-current="true"] {
  color: var(--ink-950);
  background: var(--lime-400);
  border-color: var(--lime-400);
}

/* 章节骨架 */
.page-about .chapter {
  padding-block: clamp(38px, 5.6vw, 82px);
  border-bottom: var(--about-hair);
}

.page-about .chapter:last-of-type {
  border-bottom: 0;
}

.page-about .chapter__head {
  margin-bottom: clamp(22px, 3.4vw, 44px);
}

.page-about .chapter__no {
  margin: 0 0 12px;
  font-size: var(--t-xs);
  letter-spacing: 0.18em;
  color: var(--cyan-400);
}

.page-about .chapter__title {
  margin: 0;
  max-width: 24ch;
  font-family: var(--font-head);
  font-weight: 300;
  font-size: clamp(25px, 4vw, 40px);
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: var(--white-050);
}

.page-about .chapter__body {
  display: grid;
  gap: clamp(22px, 3vw, 40px);
  align-items: start;
}

.page-about .about-figure {
  grid-column: 1 / -1;
  margin: 0;
}

.page-about .about-figure img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
  border-radius: var(--r-md);
}

/* 正文与右侧注释 */
.page-about .prose p,
.page-about .prose-intro {
  margin: 0 0 16px;
  max-width: 62ch;
  font-size: var(--t-sm);
  line-height: 1.8;
  color: var(--slate-300);
}

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

.page-about .prose a {
  color: var(--cyan-400);
  text-decoration: underline;
  text-underline-offset: 3px;
}

.page-about .prose a:hover,
.page-about .prose a:focus-visible {
  color: var(--lime-400);
}

.page-about .chapter__side {
  display: grid;
  gap: 14px;
  align-content: start;
}

.page-about .side-note {
  display: grid;
  gap: 4px;
  margin: 0;
}

.page-about .side-note__k {
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.08em;
  color: var(--cyan-200);
}

.page-about .side-note__v {
  font-family: var(--font-mono);
  font-size: var(--t-sm);
  line-height: 1.5;
  color: var(--white-050);
}

.page-about .side-note__v a {
  color: var(--cyan-400);
  text-decoration: underline;
  text-underline-offset: 3px;
}

.page-about .side-note__v a:hover,
.page-about .side-note__v a:focus-visible {
  color: var(--lime-400);
}

.page-about .side-note--accent .side-note__v {
  color: var(--lime-400);
}

/* 版本历程 */
.page-about .era-list {
  margin-top: clamp(18px, 2.4vw, 28px);
  border-top: var(--about-hair);
}

.page-about .era {
  border-bottom: var(--about-hair);
}

.page-about .era__trigger {
  display: grid;
  grid-template-columns: 48px minmax(0, 1fr) 16px;
  align-items: center;
  gap: 14px;
  width: 100%;
  padding: 16px 0;
  background: transparent;
  border: 0;
  color: var(--white-050);
  font: inherit;
  text-align: left;
  cursor: pointer;
}

.page-about .era__tag {
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.1em;
  color: var(--cyan-400);
}

.page-about .era__name {
  font-size: var(--t-sm);
  line-height: 1.5;
  color: var(--slate-300);
  transition: color 0.18s var(--ease);
}

.page-about .era__trigger:hover .era__name,
.page-about .era__trigger:focus-visible .era__name,
.page-about .era__trigger[aria-expanded="true"] .era__name {
  color: var(--white-050);
}

.page-about .era__mark {
  position: relative;
  justify-self: end;
  width: 16px;
  height: 16px;
  border: 1px solid var(--ink-700);
  border-radius: 5px;
  transition: border-color 0.18s var(--ease);
}

.page-about .era__trigger[aria-expanded="true"] .era__mark {
  border-color: var(--lime-400);
}

.page-about .era__mark::before,
.page-about .era__mark::after {
  content: "";
  position: absolute;
  left: 50%;
  top: 50%;
  translate: -50% -50%;
  background: var(--cyan-400);
}

.page-about .era__mark::before {
  width: 8px;
  height: 1px;
}

.page-about .era__mark::after {
  width: 1px;
  height: 8px;
  transition: opacity 0.18s var(--ease);
}

.page-about .era__trigger[aria-expanded="true"] .era__mark::before {
  background: var(--lime-400);
}

.page-about .era__trigger[aria-expanded="true"] .era__mark::after {
  opacity: 0;
}

.page-about .era__panel {
  padding: 0 0 20px 62px;
}

.page-about .era__panel p {
  margin: 0;
  max-width: 58ch;
  font-size: var(--t-sm);
  line-height: 1.75;
  color: var(--slate-300);
}

/* 职能列表 */
.page-about .role-list {
  display: grid;
  gap: 0;
  margin: clamp(20px, 2.6vw, 30px) 0 0;
  border-top: var(--about-hair);
}

.page-about .role {
  display: grid;
  gap: 6px;
  padding: 16px 0;
  border-bottom: var(--about-hair);
}

.page-about .role dt {
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.08em;
  color: var(--cyan-200);
}

.page-about .role dd {
  margin: 0;
  max-width: 58ch;
  font-size: var(--t-sm);
  line-height: 1.75;
  color: var(--slate-300);
}

.page-about .role-list + .prose-intro {
  margin-top: clamp(20px, 2.6vw, 30px);
}

/* 自我衡量 */
.page-about .metric-list {
  display: grid;
  gap: 0;
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: var(--about-hair);
}

.page-about .metric-list li {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: baseline;
  gap: 14px;
  padding: 15px 0;
  border-bottom: var(--about-hair);
}

.page-about .metric-list__label {
  font-size: var(--t-sm);
  line-height: 1.6;
  color: var(--slate-300);
}

.page-about .metric-list__value {
  font-family: var(--font-mono);
  font-size: var(--t-sm);
  letter-spacing: 0.02em;
  color: var(--cyan-400);
  white-space: nowrap;
}

/* 中等屏幕及以上 */
@media (min-width: 900px) {
  .page-about .chapter__body {
    grid-template-columns: minmax(0, 1fr) var(--about-side-w);
    gap: clamp(32px, 5vw, 72px);
  }

  .page-about .chapter__side {
    border-left: 1px dashed var(--ink-700);
    padding-left: 22px;
    padding-top: 4px;
  }

  .page-about .role {
    grid-template-columns: 104px minmax(0, 1fr);
    gap: 22px;
    align-items: baseline;
  }

  .page-about .era__trigger {
    grid-template-columns: 56px minmax(0, 1fr) 18px;
    gap: 18px;
  }

  .page-about .era__panel {
    padding-left: 74px;
  }
}

@media (max-width: 560px) {
  .page-about .about-hero h1 {
    max-width: none;
  }

  .page-about .hero-figures {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 14px 18px;
  }

  .page-about .chapter-index {
    flex-wrap: nowrap;
    overflow-x: auto;
    padding-bottom: 18px;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
  }

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

  .page-about .chapter-index a {
    flex: 0 0 auto;
  }

  .page-about .era__panel {
    padding-left: 0;
  }

  .page-about .metric-list li {
    grid-template-columns: minmax(0, 1fr);
    gap: 6px;
  }
}