.page-about {
  background: var(--ink);
  color: var(--text);
  overflow-x: clip;
}

/* ---------- hero ---------- */
.page-about .ab-hero {
  position: relative;
  overflow: hidden;
  border-bottom: 1px solid var(--line);
  background:
    radial-gradient(620px 340px at 84% -10%, rgba(255, 106, 44, 0.18), transparent 72%),
    radial-gradient(560px 320px at 4% 8%, rgba(34, 224, 214, 0.13), transparent 70%);
}

.page-about .ab-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(to right, var(--line) 1px, transparent 1px),
    linear-gradient(to bottom, var(--line) 1px, transparent 1px);
  background-size: 96px 96px;
  opacity: 0.16;
  pointer-events: none;
}

.page-about .ab-hero-inner {
  position: relative;
  max-width: var(--maxw);
  margin: 0 auto;
  padding: clamp(18px, 3vw, 32px) var(--gutter) clamp(44px, 7vw, 88px);
}

.page-about .ab-hero-grid {
  display: grid;
  gap: 28px;
  margin-top: clamp(20px, 4vw, 44px);
}

.page-about .ab-rail {
  display: none;
  border-left: 1px solid var(--line);
  padding-left: 14px;
}

.page-about .ab-rail-text {
  writing-mode: vertical-rl;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.24em;
  color: var(--muted);
  white-space: nowrap;
}

.page-about .ab-kicker {
  display: inline-block;
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--cyan);
}

.page-about .ab-title {
  margin: 0;
  max-width: 16em;
  font-size: clamp(28px, 6.4vw, 58px);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.025em;
  color: var(--text);
  transform: scaleX(0.97);
  transform-origin: left center;
}

.page-about .ab-title em {
  font-style: normal;
  color: var(--orange);
}

.page-about .ab-lede {
  margin: 22px 0 0;
  max-width: 38em;
  font-size: 15.5px;
  line-height: 1.85;
  color: var(--muted);
}

.page-about .ab-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 28px;
}

.page-about .ab-hero-side {
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: linear-gradient(160deg, rgba(15, 33, 56, 0.94), rgba(14, 42, 51, 0.72));
  padding: 8px 20px;
}

.page-about .ab-side-item {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 14px;
  padding: 14px 0;
  border-bottom: 1px dashed rgba(30, 58, 95, 0.9);
}

.page-about .ab-side-item:last-child {
  border-bottom: 0;
}

.page-about .ab-side-key {
  font-size: 12.5px;
  color: var(--muted);
  letter-spacing: 0.04em;
}

.page-about .ab-side-val {
  font-size: 15px;
  font-weight: 800;
  color: var(--text);
}

.page-about .ab-side-val--mono {
  font-family: var(--font-mono);
  color: var(--amber);
  font-variant-numeric: tabular-nums;
}

/* ---------- sticky index ---------- */
.page-about .ab-index {
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(10, 22, 40, 0.94);
  border-bottom: 1px solid var(--line);
}

.page-about .ab-index ol {
  display: flex;
  gap: 4px;
  list-style: none;
  margin: 0 auto;
  max-width: var(--maxw);
  padding: 10px var(--gutter);
  overflow-x: auto;
  scrollbar-width: none;
}

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

.page-about .ab-index li {
  flex: 0 0 auto;
}

.page-about .ab-index a {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  padding: 8px 14px;
  border: 1px solid transparent;
  border-radius: 999px;
  font-size: 13px;
  color: var(--muted);
  text-decoration: none;
  white-space: nowrap;
  transition: color 0.2s ease, border-color 0.2s ease, background 0.2s ease;
}

.page-about .ab-index a span {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  color: var(--cyan);
}

.page-about .ab-index a:hover,
.page-about .ab-index a:focus-visible {
  color: var(--text);
  border-color: var(--line);
  outline: none;
}

.page-about .ab-index a[aria-current],
.page-about .ab-index a.is-current {
  color: var(--text);
  border-color: var(--orange);
  background: rgba(255, 106, 44, 0.13);
}

/* ---------- chapters ---------- */
.page-about .ab-chapter {
  position: relative;
  padding: clamp(52px, 8vw, 104px) 0;
  border-top: 1px solid var(--line);
}

.page-about .ab-chapter--paper {
  background: var(--paper);
  color: #16283d;
}

.page-about .ab-ch-head {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  gap: 14px 26px;
  margin-bottom: clamp(24px, 4vw, 42px);
}

.page-about .ab-ch-num {
  font-family: var(--font-mono);
  font-weight: 800;
  font-size: clamp(54px, 10vw, 124px);
  line-height: 0.78;
  letter-spacing: -0.05em;
  color: var(--panel);
  -webkit-text-stroke: 1.5px var(--line);
}

.page-about .ab-chapter--paper .ab-ch-num {
  color: rgba(22, 40, 61, 0.14);
  -webkit-text-stroke: 1.5px rgba(22, 40, 61, 0.42);
}

.page-about .ab-ch-kicker {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--cyan);
}

.page-about .ab-chapter--paper .ab-ch-kicker {
  color: #0f7d78;
}

.page-about .ab-ch-title {
  margin: 0;
  max-width: 20em;
  font-size: clamp(22px, 3.4vw, 36px);
  font-weight: 800;
  line-height: 1.25;
  letter-spacing: -0.015em;
  color: var(--text);
}

.page-about .ab-chapter--paper .ab-ch-title {
  color: #10243c;
}

.page-about .ab-p {
  margin: 0 0 22px;
  max-width: 40em;
  font-size: 15px;
  line-height: 1.85;
  color: var(--muted);
}

.page-about .ab-p--lead {
  margin-bottom: clamp(24px, 4vw, 40px);
}

.page-about .ab-chapter--paper .ab-p {
  color: #44586f;
}

.page-about .ab-p--after {
  margin-top: 24px;
  margin-bottom: 0;
}

/* ---------- split ---------- */
.page-about .ab-split {
  display: grid;
  gap: 30px;
}

/* ---------- layer cards ---------- */
.page-about .ab-layers {
  display: grid;
  gap: 14px;
}

.page-about .ab-layer {
  position: relative;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: rgba(15, 33, 56, 0.72);
  padding: 24px 20px 20px;
}

.page-about .ab-layer::before {
  content: "";
  position: absolute;
  top: 0;
  left: 20px;
  width: 34px;
  height: 3px;
  border-radius: 0 0 3px 3px;
  background: var(--orange);
}

.page-about .ab-layer:nth-child(2)::before {
  background: var(--cyan);
}

.page-about .ab-layer:nth-child(3)::before {
  background: var(--amber);
}

.page-about .ab-layer-title {
  margin: 0 0 10px;
  font-size: 16px;
  font-weight: 800;
  letter-spacing: 0.01em;
  color: var(--text);
}

.page-about .ab-layer-text {
  margin: 0;
  font-size: 13.8px;
  line-height: 1.8;
  color: var(--muted);
}

/* ---------- figures ---------- */
.page-about .ab-figure {
  margin: 0;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--panel);
}

.page-about .ab-figure--wide {
  margin-top: clamp(28px, 5vw, 52px);
}

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

.page-about .ab-figure figcaption {
  padding: 12px 16px;
  border-top: 1px solid var(--line);
  background: rgba(14, 42, 51, 0.55);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.06em;
  color: var(--muted);
}

/* ---------- diagonal timeline ---------- */
.page-about .ab-timeline {
  position: relative;
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 16px;
}

.page-about .ab-timeline::before {
  content: "";
  position: absolute;
  top: 6%;
  left: 0;
  width: 82%;
  height: 1px;
  background: linear-gradient(90deg, rgba(34, 224, 214, 0.55), rgba(255, 106, 44, 0.5), transparent);
  transform: rotate(7deg);
  transform-origin: left center;
  pointer-events: none;
  display: none;
}

.page-about .ab-node {
  position: relative;
  z-index: 1;
}

.page-about .ab-node details {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: rgba(15, 33, 56, 0.88);
  overflow: hidden;
  transition: border-color 0.2s ease;
}

.page-about .ab-node details:hover,
.page-about .ab-node details[open] {
  border-color: rgba(255, 106, 44, 0.6);
}

.page-about .ab-node summary {
  display: grid;
  grid-template-columns: auto auto 1fr auto;
  align-items: center;
  gap: 12px;
  padding: 16px 18px;
  cursor: pointer;
  list-style: none;
}

.page-about .ab-node summary::-webkit-details-marker {
  display: none;
}

.page-about .ab-node summary:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: -2px;
}

.page-about .ab-node-dot {
  width: 11px;
  height: 11px;
  border-radius: 50%;
  border: 2px solid var(--orange);
  background: transparent;
}

.page-about .ab-node details[open] .ab-node-dot {
  background: var(--orange);
}

.page-about .ab-node-ver {
  font-family: var(--font-mono);
  font-size: 17px;
  font-weight: 800;
  letter-spacing: 0.04em;
  color: var(--amber);
}

.page-about .ab-node-name {
  font-size: 15px;
  font-weight: 700;
  color: var(--text);
}

.page-about .ab-node-arrow {
  font-family: var(--font-mono);
  font-size: 17px;
  color: var(--muted);
  transition: transform 0.2s ease, color 0.2s ease;
}

.page-about .ab-node details[open] .ab-node-arrow {
  transform: rotate(45deg);
  color: var(--orange);
}

.page-about .ab-node-body {
  padding: 0 18px 18px 41px;
}

.page-about .ab-node-body p {
  margin: 0;
  font-size: 13.8px;
  line-height: 1.85;
  color: var(--muted);
}

/* ---------- phase switcher ---------- */
.page-about .ab-phase-deck {
  position: relative;
}

.page-about .ab-phase-radio {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
  pointer-events: none;
}

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

.page-about .ab-phase-tab {
  display: inline-block;
  padding: 10px 18px;
  border: 1px solid var(--line);
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--muted);
  cursor: pointer;
  transition: color 0.2s ease, border-color 0.2s ease, background 0.2s ease;
}

.page-about .ab-phase-tab:hover {
  color: var(--text);
  border-color: var(--muted);
}

.page-about #ab-phase-1:checked ~ .ab-phase-tabs label[for="ab-phase-1"],
.page-about #ab-phase-2:checked ~ .ab-phase-tabs label[for="ab-phase-2"],
.page-about #ab-phase-3:checked ~ .ab-phase-tabs label[for="ab-phase-3"] {
  background: var(--orange);
  border-color: var(--orange);
  color: var(--ink);
  font-weight: 700;
}

.page-about .ab-phase-panel {
  display: none;
  border: 1px solid var(--line);
  border-left: 3px solid var(--orange);
  border-radius: var(--radius);
  background: rgba(15, 33, 56, 0.7);
  padding: 22px 20px;
}

.page-about #ab-phase-1:checked ~ .ab-phase-panels .ab-panel-1,
.page-about #ab-phase-2:checked ~ .ab-phase-panels .ab-panel-2,
.page-about #ab-phase-3:checked ~ .ab-phase-panels .ab-panel-3 {
  display: block;
}

.page-about .ab-panel-title {
  margin: 0 0 14px;
  font-size: 16px;
  font-weight: 800;
  color: var(--text);
}

.page-about .ab-list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 11px;
}

.page-about .ab-list li {
  position: relative;
  padding-left: 18px;
  font-size: 13.8px;
  line-height: 1.8;
  color: var(--muted);
}

.page-about .ab-list li::before {
  content: "";
  position: absolute;
  top: 9px;
  left: 0;
  width: 7px;
  height: 1px;
  background: var(--cyan);
}

/* ---------- fields ---------- */
.page-about .ab-fields {
  display: grid;
  gap: 12px;
  margin-bottom: clamp(26px, 4vw, 42px);
}

.page-about .ab-field {
  border: 1px solid rgba(22, 40, 61, 0.24);
  border-radius: var(--radius);
  background: rgba(255, 255, 255, 0.62);
  padding: 18px 18px 16px;
}

.page-about .ab-field-tag {
  display: inline-block;
  margin-bottom: 9px;
  padding: 4px 10px;
  border-radius: 4px;
  background: #10243c;
  color: var(--paper);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
}

.page-about .ab-field-text {
  margin: 0;
  font-size: 13.8px;
  line-height: 1.8;
  color: #44586f;
}

.page-about .ab-note-grid {
  display: grid;
  gap: 16px;
}

.page-about .ab-note {
  border-left: 3px solid #10243c;
  padding-left: 18px;
}

.page-about .ab-note--stat {
  border-left-color: #d9541e;
  display: flex;
  align-items: baseline;
  gap: 14px;
  flex-wrap: wrap;
}

.page-about .ab-note-title {
  margin: 0 0 10px;
  font-size: 16px;
  font-weight: 800;
  color: #10243c;
}

.page-about .ab-note-text {
  margin: 0;
  max-width: 40em;
  font-size: 14px;
  line-height: 1.85;
  color: #44586f;
}

.page-about .ab-stat-num {
  margin: 0;
  font-family: var(--font-mono);
  font-size: clamp(46px, 8vw, 76px);
  font-weight: 800;
  line-height: 0.9;
  letter-spacing: -0.04em;
  color: #d9541e;
  font-variant-numeric: tabular-nums;
}

.page-about .ab-stat-label {
  margin: 0;
  max-width: 18em;
  font-size: 13px;
  line-height: 1.75;
  color: #44586f;
}

/* ---------- roster band ---------- */
.page-about .ab-band {
  margin: 0 0 clamp(26px, 4vw, 44px);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  padding: 16px;
}

.page-about .ab-band-track {
  display: flex;
  gap: 3px;
  height: 42px;
  border-radius: 8px;
  overflow: hidden;
}

.page-about .ab-band-seg {
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.08em;
  color: var(--ink);
  white-space: nowrap;
  overflow: hidden;
}

.page-about .ab-band-seg--pre {
  flex: 28 1 0;
  background: rgba(34, 224, 214, 0.78);
}

.page-about .ab-band-seg--live {
  flex: 56 1 0;
  background: var(--orange);
  font-weight: 700;
}

.page-about .ab-band-seg--post {
  flex: 16 1 0;
  background: rgba(255, 194, 75, 0.82);
}

.page-about .ab-band-scale {
  display: flex;
  justify-content: space-between;
  margin-top: 10px;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.06em;
  color: var(--muted);
}

/* ---------- principles ---------- */
.page-about .ab-principles {
  display: grid;
  gap: 14px;
  margin-bottom: clamp(32px, 5vw, 56px);
}

.page-about .ab-principle {
  border-top: 1px solid var(--line);
  padding-top: 16px;
}

.page-about .ab-principle-title {
  margin: 0 0 9px;
  font-size: 15.5px;
  font-weight: 800;
  color: var(--text);
}

.page-about .ab-principle p {
  margin: 0;
  font-size: 13.8px;
  line-height: 1.85;
  color: var(--muted);
}

/* ---------- cta ---------- */
.page-about .ab-cta {
  display: grid;
  gap: 20px;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background:
    radial-gradient(420px 200px at 88% 0%, rgba(34, 224, 214, 0.14), transparent 70%),
    rgba(15, 33, 56, 0.78);
  padding: clamp(22px, 4vw, 36px);
}

.page-about .ab-cta-title {
  margin: 0 0 10px;
  font-size: clamp(18px, 2.6vw, 24px);
  font-weight: 800;
  line-height: 1.35;
  color: var(--text);
}

.page-about .ab-cta-sub {
  margin: 0;
  max-width: 34em;
  font-size: 13.8px;
  line-height: 1.8;
  color: var(--muted);
}

.page-about .ab-cta-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

/* ---------- responsive ---------- */
@media (min-width: 620px) {
  .page-about .ab-fields {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .page-about .ab-note-grid {
    grid-template-columns: minmax(0, 1.4fr) minmax(0, 0.8fr);
    align-items: start;
  }

  .page-about .ab-principles {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 22px;
  }
}

@media (min-width: 760px) {
  .page-about .ab-layers {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (min-width: 900px) {
  .page-about .ab-hero-grid {
    grid-template-columns: 46px minmax(0, 1fr) 286px;
    gap: 42px;
    align-items: start;
  }

  .page-about .ab-rail {
    display: block;
  }

  .page-about .ab-split {
    grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
    gap: 48px;
    align-items: start;
  }

  .page-about .ab-cta {
    grid-template-columns: minmax(0, 1fr) auto;
    align-items: center;
    gap: 32px;
  }

  .page-about .ab-cta-actions {
    justify-content: flex-end;
  }
}

@media (min-width: 980px) {
  .page-about .ab-timeline::before {
    display: block;
  }

  .page-about .ab-node:nth-child(1) {
    margin-left: 0;
  }

  .page-about .ab-node:nth-child(2) {
    margin-left: 6%;
  }

  .page-about .ab-node:nth-child(3) {
    margin-left: 12%;
  }

  .page-about .ab-node:nth-child(4) {
    margin-left: 18%;
  }

  .page-about .ab-fields {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}
<<<END>>>