.page-about {
  --ab-hair: var(--ink-700);
  --ab-panel: var(--ink-800);
  --ab-ease: var(--ease);
}

/* ---------- breadcrumb ---------- */
.page-about .breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  padding-top: clamp(20px, 4vw, 36px);
  font-family: var(--font-mono);
  font-size: var(--fs-13);
  letter-spacing: 0.04em;
  color: var(--dim);
}
.page-about .breadcrumb a {
  color: var(--dim);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 180ms var(--ab-ease), border-color 180ms var(--ab-ease);
}
.page-about .breadcrumb a:hover,
.page-about .breadcrumb a:focus-visible {
  color: var(--cy);
  border-bottom-color: var(--cy);
}
.page-about .breadcrumb__sep {
  color: var(--ink-700);
}
.page-about .breadcrumb span[aria-current] {
  color: var(--cy-soft);
}

/* ---------- hero ---------- */
.page-about .about-hero {
  padding: clamp(34px, 6vw, 76px) 0 clamp(44px, 8vw, 110px);
}
.page-about .about-hero__title {
  margin: 18px 0 0;
  max-width: 20ch;
}
.page-about .about-hero__rule {
  display: block;
  width: min(240px, 46vw);
  height: 2px;
  margin-top: clamp(20px, 3.4vw, 34px);
  background: linear-gradient(90deg, var(--cy) 0%, rgba(60, 224, 224, 0) 100%);
}
.page-about .about-hero__lead {
  margin: clamp(22px, 3.6vw, 34px) 0 0;
  max-width: 44ch;
}
.page-about .about-hero__note {
  margin: clamp(14px, 2vw, 20px) 0 0;
  max-width: 40ch;
  font-size: var(--fs-13);
  font-family: var(--font-mono);
  letter-spacing: 0.05em;
  color: var(--dim);
}

/* ---------- chain numbers ---------- */
.page-about .about-chainblock {
  padding-bottom: clamp(8px, 2vw, 20px);
}
.page-about .about-chain {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1px;
  background: var(--ab-hair);
  border-top: 1px solid var(--ab-hair);
  border-bottom: 1px solid var(--ab-hair);
}
.page-about .about-chain__item {
  background: var(--ink-900);
  padding: clamp(22px, 3.2vw, 34px) clamp(16px, 2.2vw, 26px);
}
.page-about .about-chain__label {
  margin: 0;
  font-size: var(--fs-13);
  letter-spacing: 0.16em;
  color: var(--dim);
}
.page-about .about-chain__num {
  margin: 14px 0 0;
  font-family: var(--font-mono);
  font-size: clamp(2.25rem, 7.5vw, 4rem);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--cy);
}
.page-about .about-chain__unit {
  margin-left: 8px;
  font-size: 0.26em;
  letter-spacing: 0.08em;
  color: var(--text);
}
.page-about .about-chain__desc {
  margin: 14px 0 0;
  font-size: var(--fs-16);
  line-height: 1.7;
  color: var(--text);
}

/* ---------- section shell ---------- */
.page-about .about-sec {
  padding-block: clamp(56px, 9vw, 128px);
}
.page-about .about-sec + .about-sec {
  border-top: 1px solid var(--ab-hair);
}
.page-about .about-sec__head {
  max-width: 62ch;
}
.page-about .about-sec__head h2 {
  margin: 14px 0 0;
}
.page-about .about-sec__intro {
  margin: clamp(16px, 2.4vw, 24px) 0 0;
  font-size: var(--fs-18);
  line-height: 1.8;
  color: var(--text);
}
.page-about .about-sec__intro a,
.page-about .about-node__body a,
.page-about .about-eco__desc a,
.page-about .about-close__sub a {
  color: var(--cy);
  text-decoration: none;
  border-bottom: 1px solid rgba(60, 224, 224, 0.45);
  transition: color 180ms var(--ab-ease), border-color 180ms var(--ab-ease);
}
.page-about .about-sec__intro a:hover,
.page-about .about-node__body a:hover,
.page-about .about-eco__desc a:hover,
.page-about .about-close__sub a:hover {
  color: var(--cy-soft);
  border-bottom-color: var(--cy-soft);
}

/* ---------- timeline ---------- */
.page-about .about-timeline .wrap {
  position: relative;
}
.page-about .about-vnote {
  display: none;
  writing-mode: vertical-rl;
  text-orientation: mixed;
  position: absolute;
  right: 0;
  top: clamp(120px, 12vw, 200px);
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.3em;
  color: var(--dim);
  opacity: 0.75;
  user-select: none;
}
.page-about .about-tl {
  position: relative;
  list-style: none;
  margin: clamp(30px, 5vw, 56px) 0 0;
  padding: 0 0 0 30px;
}
.page-about .about-tl::before {
  content: "";
  position: absolute;
  left: 14px;
  top: 12px;
  bottom: 12px;
  width: 1px;
  background: linear-gradient(180deg, var(--cy) 0%, var(--ink-700) 55%, rgba(22, 35, 58, 0) 100%);
}
.page-about .about-tl__item {
  position: relative;
  padding-bottom: clamp(14px, 2.6vw, 26px);
}
.page-about .about-tl__item::before {
  content: "";
  position: absolute;
  left: -21px;
  top: 24px;
  width: 11px;
  height: 11px;
  border-radius: 50%;
  background: var(--ink-900);
  border: 1px solid var(--cy);
  transition: background 200ms var(--ab-ease), box-shadow 200ms var(--ab-ease);
}
.page-about .about-tl__item:has(.about-node[open])::before {
  background: var(--cy);
  box-shadow: 0 0 0 4px rgba(60, 224, 224, 0.16);
}
.page-about .about-node {
  background: var(--ab-panel);
  border: 1px solid var(--ab-hair);
  border-radius: var(--r-md);
  overflow: hidden;
  transition: border-color 220ms var(--ab-ease), background 220ms var(--ab-ease);
}
.page-about .about-node[open] {
  border-color: rgba(60, 224, 224, 0.42);
}
.page-about .about-node > summary {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 8px 16px;
  padding: clamp(14px, 2.4vw, 20px) clamp(16px, 2.6vw, 26px);
  cursor: pointer;
  list-style: none;
}
.page-about .about-node > summary::-webkit-details-marker {
  display: none;
}
.page-about .about-node > summary::after {
  content: "＋";
  margin-left: auto;
  align-self: center;
  font-family: var(--font-mono);
  font-size: var(--fs-16);
  color: var(--cy);
}
.page-about .about-node[open] > summary::after {
  content: "−";
  color: var(--signal);
}
.page-about .about-node__year {
  font-size: clamp(1.125rem, 3vw, 1.75rem);
  font-weight: 700;
  color: var(--cy);
  letter-spacing: 0.01em;
}
.page-about .about-node__label {
  font-size: clamp(1rem, 2.2vw, 1.25rem);
  font-weight: 800;
  color: var(--head);
}
.page-about .about-node__body {
  padding: 0 clamp(16px, 2.6vw, 26px) clamp(16px, 2.6vw, 24px);
  max-width: 64ch;
  font-size: var(--fs-16);
  line-height: 1.78;
  color: var(--text);
}
.page-about .about-node__body p {
  margin: 0;
}

/* ---------- figures ---------- */
.page-about .about-fig {
  margin: clamp(30px, 5vw, 58px) 0 0;
}
.page-about .about-fig .img-frame {
  overflow: hidden;
  border-radius: var(--r-lg);
  border: 1px solid var(--ab-hair);
  background: var(--ink-800);
}
.page-about .about-fig img {
  display: block;
  width: 100%;
  height: auto;
  max-width: 100%;
  object-fit: cover;
}
.page-about .about-fig--wide img {
  aspect-ratio: 16 / 9;
}
.page-about .about-fig--lead .img-frame {
  margin-bottom: clamp(28px, 4.6vw, 52px);
}
.page-about .about-cap {
  margin: 12px 0 0;
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.04em;
  line-height: 1.7;
  color: var(--dim);
}

/* ---------- roster ---------- */
.page-about .about-tablewrap {
  margin-top: clamp(26px, 4vw, 42px);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
.page-about .about-roster {
  width: 100%;
  min-width: 520px;
  border-collapse: collapse;
  font-size: var(--fs-16);
}
.page-about .about-roster thead th {
  padding: 10px 14px;
  text-align: left;
  font-size: var(--fs-13);
  font-weight: 600;
  letter-spacing: 0.1em;
  color: var(--dim);
  border-bottom: 1px solid var(--ab-hair);
}
.page-about .about-roster tbody th {
  padding: 16px 14px;
  text-align: left;
  font-weight: 700;
  color: var(--head);
  border-bottom: 1px solid var(--ab-hair);
}
.page-about .about-roster tbody td {
  padding: 16px 14px;
  color: var(--text);
  border-bottom: 1px solid var(--ab-hair);
  vertical-align: top;
}
.page-about .about-roster .num {
  text-align: right;
  font-family: var(--font-mono);
  font-size: var(--fs-18);
  font-weight: 700;
  color: var(--cy);
  white-space: nowrap;
}

/* ---------- process ---------- */
.page-about .about-proc {
  display: grid;
  grid-template-columns: 1fr;
  gap: 10px;
  margin-top: clamp(24px, 3.6vw, 36px);
}
.page-about .about-proc__step {
  margin: 0;
  padding: 14px 18px;
  border-left: 2px solid var(--cy);
  background: var(--ab-panel);
  border-radius: 0 var(--r-sm) var(--r-sm) 0;
  font-size: var(--fs-16);
  color: var(--text);
}
.page-about .about-proc__step .mono {
  margin-right: 10px;
  color: var(--signal);
  font-size: var(--fs-13);
}
.page-about .about-proc__note {
  margin: clamp(18px, 2.6vw, 26px) 0 0;
  max-width: 58ch;
  font-size: var(--fs-16);
  line-height: 1.78;
  color: var(--dim);
}

/* ---------- cadence ---------- */
.page-about .about-cadence__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(26px, 4.4vw, 52px);
  margin-top: clamp(26px, 4vw, 44px);
}
.page-about .about-beats {
  list-style: none;
  margin: 0;
  padding: 0;
}
.page-about .about-beats__item {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: baseline;
  column-gap: 16px;
  row-gap: 6px;
  padding: 16px 0;
  border-bottom: 1px solid var(--ab-hair);
}
.page-about .about-beats__item:first-child {
  border-top: 1px solid var(--ab-hair);
}
.page-about .about-beats__name {
  margin: 0;
  font-size: var(--fs-18);
  font-weight: 700;
  color: var(--head);
}
.page-about .about-beats__freq {
  margin: 0;
  font-size: var(--fs-13);
  letter-spacing: 0.05em;
  color: var(--cy);
  white-space: nowrap;
}
.page-about .about-beats__note {
  grid-column: 1 / -1;
  margin: 0;
  font-size: var(--fs-16);
  line-height: 1.7;
  color: var(--dim);
}
.page-about .about-fig--side {
  margin-top: 0;
}
.page-about .about-fig--side img {
  aspect-ratio: 27 / 19;
}

/* ---------- scale ---------- */
.page-about .about-scale__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(22px, 3.4vw, 36px);
  margin-top: clamp(30px, 5vw, 52px);
}
.page-about .about-scale__cell {
  padding-top: 18px;
  border-top: 2px solid var(--cy);
}
.page-about .about-scale__num {
  margin: 0;
  font-size: clamp(2.6rem, 8.5vw, 4.5rem);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.03em;
  color: var(--head);
}
.page-about .about-scale__unit {
  margin-left: 8px;
  font-size: 0.26em;
  letter-spacing: 0.06em;
  color: var(--cy);
}
.page-about .about-scale__label {
  margin: 14px 0 0;
  font-size: var(--fs-16);
  color: var(--text);
}
.page-about .about-scale__foot {
  margin: clamp(28px, 4.4vw, 46px) 0 0;
  max-width: 60ch;
  font-size: var(--fs-18);
  line-height: 1.8;
  color: var(--text);
}
.page-about .about-plate {
  display: inline-block;
  margin: clamp(22px, 3.4vw, 34px) 0 0;
  padding: 12px 16px;
  max-width: 42ch;
  background: var(--paper);
  color: var(--paper-ink);
  border-radius: var(--r-sm);
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.04em;
  line-height: 1.6;
}

/* ---------- eco ---------- */
.page-about .about-eco {
  list-style: none;
  margin: clamp(26px, 4vw, 44px) 0 0;
  padding: 0;
}
.page-about .about-eco__item {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 16px;
  padding: clamp(18px, 2.8vw, 28px) 0;
  border-top: 1px solid var(--ab-hair);
}
.page-about .about-eco__item:last-child {
  border-bottom: 1px solid var(--ab-hair);
}
.page-about .about-eco__no {
  padding-top: 8px;
  font-size: var(--fs-13);
  letter-spacing: 0.1em;
  color: var(--signal);
}
.page-about .about-eco__title {
  margin: 0;
  font-size: clamp(1.25rem, 3vw, 1.75rem);
  font-weight: 800;
  color: var(--head);
}
.page-about .about-eco__desc {
  margin: 10px 0 0;
  max-width: 62ch;
  font-size: var(--fs-16);
  line-height: 1.78;
  color: var(--text);
}
.page-about .about-eco__foot {
  margin: clamp(24px, 3.6vw, 38px) 0 0;
  padding-left: 18px;
  border-left: 2px solid var(--lime);
  font-size: var(--fs-16);
  line-height: 1.75;
  color: var(--text);
}

/* ---------- close ---------- */
.page-about .about-close {
  padding-block: clamp(56px, 9vw, 128px) clamp(64px, 10vw, 140px);
  border-top: 1px solid var(--ab-hair);
}
.page-about .about-close__big {
  margin: 0;
  font-size: clamp(3.5rem, 14vw, 9rem);
  font-weight: 700;
  line-height: 0.9;
  letter-spacing: -0.04em;
  color: var(--signal);
}
.page-about .about-close__unit {
  margin-left: 10px;
  font-size: 0.2em;
  letter-spacing: 0.08em;
  color: var(--text);
}
.page-about .about-close__line {
  margin: clamp(20px, 3vw, 30px) 0 0;
  max-width: 30ch;
  font-size: clamp(1.25rem, 3.6vw, 2rem);
  font-weight: 800;
  line-height: 1.4;
  color: var(--head);
}
.page-about .about-close__sub {
  margin: clamp(14px, 2.2vw, 20px) 0 0;
  max-width: 56ch;
  font-size: var(--fs-16);
  line-height: 1.78;
  color: var(--text);
}
.page-about .about-close__cta {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  margin-top: clamp(24px, 3.6vw, 36px);
}

/* ---------- media ---------- */
@media (min-width: 720px) {
  .page-about .about-chain {
    grid-template-columns: repeat(3, 1fr);
  }
  .page-about .about-proc {
    grid-template-columns: repeat(2, 1fr);
  }
  .page-about .about-scale__grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

@media (min-width: 900px) {
  .page-about .about-cadence__grid {
    grid-template-columns: 1.15fr 0.85fr;
    align-items: start;
  }
  .page-about .about-hero__lead {
    max-width: 56ch;
  }
}

@media (min-width: 1080px) {
  .page-about .about-vnote {
    display: block;
  }
  .page-about .about-tl {
    padding-left: 40px;
  }
  .page-about .about-tl::before {
    left: 14px;
  }
  .page-about .about-tl__item::before {
    left: -31px;
  }
  .page-about .about-timeline .wrap {
    padding-right: clamp(48px, 5vw, 72px);
  }
  .page-about .about-eco__item {
    grid-template-columns: 72px 1fr;
    gap: 24px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-node,
  .page-about .about-tl__item::before,
  .page-about .breadcrumb a {
    transition: none;
  }
}