.page-about {
  --about-accent: var(--color-accent);
  --about-bg: var(--color-bg);
  --about-surface: var(--color-surface);
  --about-line: var(--color-line);
  --about-line-deep: var(--color-line-deep);
  --about-text: var(--color-text);
  --about-muted: var(--color-text-secondary);
  --about-green: var(--color-green);
  --about-blue: var(--color-link);
  --about-mono: var(--font-mono);
  --about-sans: var(--font-sans);
  --about-gap: clamp(1.5rem, 4vw, 3rem);
  position: relative;
  color: var(--about-text);
  font-family: var(--about-sans);
  background: var(--about-bg);
}

.page-about .breadcrumb {
  margin-bottom: var(--about-gap);
}

.page-about .manual-cover {
  position: relative;
  margin-bottom: clamp(2rem, 6vw, 4rem);
  border: 3px solid var(--about-text);
  background: var(--about-surface);
  box-shadow: 10px 10px 0 rgba(0, 0, 0, 0.65);
  padding: clamp(1.25rem, 3vw, 2.5rem);
  overflow: hidden;
}

.page-about .manual-cover::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 6px;
  height: 100%;
  background: var(--about-accent);
}

.page-about .cover-layout {
  display: grid;
  gap: 2rem;
  align-items: center;
}

.page-about .cover-kicker {
  font-family: var(--about-mono);
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--about-accent);
  margin: 0 0 0.75rem;
}

.page-about .cover-copy h1 {
  font-size: clamp(2.25rem, 5vw, 3.5rem);
  font-weight: 900;
  letter-spacing: -0.02em;
  line-height: 1.1;
  transform: skew(-5deg);
  transform-origin: left center;
  margin: 0 0 1rem;
}

.page-about .cover-lead {
  font-size: clamp(1rem, 1.5vw, 1.125rem);
  line-height: 1.8;
  color: var(--about-muted);
  max-width: 34em;
  margin: 0 0 1.5rem;
}

.page-about .cover-facts {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  padding: 0;
  margin: 0 0 1.25rem;
  font-family: var(--about-mono);
  font-size: 0.9rem;
}

.page-about .cover-facts li {
  display: flex;
  align-items: baseline;
  gap: 0.4rem;
  padding: 0.4rem 0.7rem;
  border: 1px solid var(--about-line-deep);
  background: var(--about-bg);
}

.page-about .cover-fact-label {
  color: var(--about-muted);
  font-size: 0.75rem;
  letter-spacing: 0.06em;
}

.page-about .cover-meta-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.page-about .cover-sigil {
  position: relative;
  width: 100%;
  max-width: 320px;
  justify-self: center;
}

.page-about .sigil-frame {
  display: grid;
  gap: 0.35rem;
  border: 3px solid var(--about-text);
  background: var(--about-bg);
  box-shadow: 8px 8px 0 var(--about-accent);
  padding: clamp(1rem, 3vw, 1.75rem);
  text-align: center;
  position: relative;
  z-index: 1;
}

.page-about .sigil-main {
  font-family: var(--about-mono);
  font-size: clamp(2.5rem, 6vw, 3.75rem);
  font-weight: 900;
  line-height: 1;
  color: var(--about-text);
  letter-spacing: -0.04em;
}

.page-about .sigil-sub {
  font-family: var(--about-mono);
  font-size: 0.8rem;
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--about-accent);
}

.page-about .sigil-code {
  font-family: var(--about-mono);
  font-size: 0.7rem;
  letter-spacing: 0.12em;
  color: var(--about-muted);
}

.page-about .sigil-corner {
  position: absolute;
  width: 42px;
  height: 42px;
  border: 3px solid var(--about-accent);
  z-index: 0;
}

.page-about .sigil-corner-a {
  top: -16px;
  right: -16px;
  border-bottom: 0;
  border-left: 0;
}

.page-about .sigil-corner-b {
  bottom: -16px;
  left: -16px;
  border-top: 0;
  border-right: 0;
}

.page-about .manual-toc {
  display: grid;
  gap: 1.25rem;
  margin-bottom: clamp(2rem, 6vw, 4rem);
  border: 2px solid var(--about-line-deep);
  background: var(--about-surface);
  box-shadow: 6px 6px 0 rgba(0, 0, 0, 0.5);
  padding: clamp(1.25rem, 3vw, 2rem);
}

.page-about .toc-intro {
  display: flex;
  align-items: baseline;
  gap: 1rem;
}

.page-about .toc-code {
  font-family: var(--about-mono);
  font-size: 0.8rem;
  letter-spacing: 0.16em;
  color: var(--about-accent);
}

.page-about .toc-intro h2 {
  font-size: 1.5rem;
  font-weight: 700;
  margin: 0;
}

.page-about .toc-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  gap: 0.75rem;
}

.page-about .toc-item a {
  display: grid;
  grid-template-columns: 3rem 1fr;
  gap: 0.5rem 1rem;
  padding: 0.75rem 1rem;
  border: 1px solid var(--about-line);
  background: var(--about-bg);
  text-decoration: none;
  color: var(--about-text);
  transition: border-color var(--ease-out), background var(--ease-out);
}

.page-about .toc-item a:hover {
  border-color: var(--about-accent);
  background: rgba(230, 57, 70, 0.08);
}

.page-about .toc-num {
  font-family: var(--about-mono);
  font-size: 1rem;
  color: var(--about-accent);
  font-weight: 700;
}

.page-about .toc-name {
  font-size: 1.1rem;
  font-weight: 700;
}

.page-about .toc-note {
  grid-column: 2;
  font-size: 0.875rem;
  color: var(--about-muted);
  margin-top: -0.5rem;
}

.page-about .manual-chapter {
  margin-bottom: clamp(1.75rem, 4vw, 3.5rem);
}

.page-about .chapter-details {
  border: 3px solid var(--about-text);
  background: var(--about-surface);
  box-shadow: 8px 8px 0 rgba(0, 0, 0, 0.6);
}

.page-about .chapter-summary {
  list-style: none;
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: clamp(1rem, 2.5vw, 1.5rem);
  cursor: pointer;
  border-bottom: 2px solid var(--about-line);
  user-select: none;
}

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

.page-about .chapter-index {
  font-family: var(--about-mono);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--about-accent);
  min-width: 2.25rem;
}

.page-about .chapter-title {
  font-size: clamp(1.35rem, 3vw, 1.75rem);
  font-weight: 800;
  margin: 0;
  transform: skew(-4deg);
  transform-origin: left center;
}

.page-about .chapter-tag {
  margin-left: auto;
}

.page-about .chapter-toggle {
  font-family: var(--about-mono);
  font-size: 1.4rem;
  color: var(--about-text);
  display: inline-block;
  transition: transform var(--ease-out);
}

.page-about .chapter-details[open] .chapter-toggle {
  transform: rotate(45deg);
  color: var(--about-accent);
}

.page-about .chapter-content {
  padding: clamp(1.25rem, 3vw, 2.25rem);
}

.page-about .chapter-grid {
  display: grid;
  gap: clamp(1.5rem, 4vw, 3rem);
  align-items: start;
}

.page-about .chapter-grid-boundary {
  align-items: start;
}

.page-about .chapter-subtitle {
  font-size: 1.25rem;
  font-weight: 700;
  margin: 0 0 1.25rem;
  color: var(--about-text);
}

.page-about .chapter-paragraph {
  color: var(--about-muted);
  line-height: 1.8;
  margin: 0 0 1.5rem;
}

.page-about .principle-list,
.page-about .scenario-list {
  display: grid;
  gap: 1.25rem;
}

.page-about .principle-item,
.page-about .scenario-item {
  padding: 1.25rem;
  border: 1px solid var(--about-line-deep);
  background: var(--about-bg);
  position: relative;
}

.page-about .principle-item h3,
.page-about .scenario-item h3 {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 1.15rem;
  font-weight: 700;
  margin: 0 0 0.6rem;
}

.page-about .principle-code,
.page-about .scenario-code {
  font-family: var(--about-mono);
  font-size: 0.75rem;
  color: var(--about-accent);
  background: rgba(230, 57, 70, 0.12);
  padding: 0.2rem 0.5rem;
}

.page-about .principle-item p,
.page-about .scenario-item p {
  margin: 0;
  color: var(--about-muted);
  line-height: 1.75;
}

.page-about .chapter-figure {
  margin: 0;
  border: 2px solid var(--about-line-deep);
  background: var(--about-bg);
  padding: 0.75rem;
}

.page-about .chapter-figure img,
.page-about .rhythm-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  border: 1px solid var(--about-line);
}

.page-about .chapter-figure figcaption,
.page-about .rhythm-figure figcaption {
  font-family: var(--about-mono);
  font-size: 0.8rem;
  color: var(--about-muted);
  padding: 0.75rem 0.25rem 0.15rem;
  letter-spacing: 0.05em;
}

.page-about .boundary-grid {
  display: grid;
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.page-about .boundary-card {
  border: 2px solid var(--about-line-deep);
  background: var(--about-bg);
  padding: 1.25rem;
}

.page-about .boundary-card-muted {
  border-style: dashed;
}

.page-about .boundary-label {
  display: inline-block;
  font-family: var(--about-mono);
  font-size: 0.75rem;
  letter-spacing: 0.1em;
  color: var(--about-accent);
  border: 1px solid var(--about-accent);
  padding: 0.2rem 0.6rem;
  margin-bottom: 0.9rem;
}

.page-about .boundary-card-muted .boundary-label {
  color: var(--about-blue);
  border-color: var(--about-blue);
}

.page-about .boundary-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  gap: 0.5rem;
}

.page-about .boundary-list li {
  padding-left: 1.25rem;
  position: relative;
  color: var(--about-muted);
  line-height: 1.6;
}

.page-about .boundary-list li::before {
  content: "—";
  position: absolute;
  left: 0;
  color: var(--about-accent);
  font-family: var(--about-mono);
}

.page-about .boundary-card-muted .boundary-list li::before {
  color: var(--about-blue);
}

.page-about .chapter-aside {
  min-width: 0;
}

.page-about .scope-panel {
  border: 2px solid var(--about-text);
  background: var(--about-bg);
  box-shadow: 6px 6px 0 rgba(0, 0, 0, 0.5);
  padding: 1.25rem;
  position: sticky;
  top: 1.5rem;
}

.page-about .scope-label {
  display: block;
  font-family: var(--about-mono);
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  color: var(--about-green);
  margin-bottom: 1rem;
}

.page-about .scope-list {
  margin: 0;
  display: grid;
  gap: 0.6rem;
}

.page-about .scope-row {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  padding-bottom: 0.6rem;
  border-bottom: 1px solid var(--about-line);
}

.page-about .scope-row dt {
  color: var(--about-muted);
  font-size: 0.875rem;
}

.page-about .scope-row dd {
  margin: 0;
  font-family: var(--about-mono);
  font-size: 0.875rem;
  font-weight: 700;
  text-align: right;
}

.page-about .chapter-rhythm {
  display: grid;
  gap: 1.5rem;
}

.page-about .rhythm-timeline {
  display: grid;
  grid-auto-columns: minmax(200px, 220px);
  grid-auto-flow: column;
  gap: 1rem;
  overflow-x: auto;
  padding: 1rem 1rem 1.25rem;
  border: 2px solid var(--about-line-deep);
  background: var(--about-bg);
  scrollbar-width: thin;
  scrollbar-color: var(--about-accent) var(--about-line);
}

.page-about .rhythm-item {
  position: relative;
  padding: 1.1rem;
  border: 1px solid var(--about-line-deep);
  background: var(--about-surface);
  min-height: 130px;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.page-about .rhythm-item::before {
  content: "";
  position: absolute;
  top: -1rem;
  left: 1.1rem;
  width: 2px;
  height: 1rem;
  background: var(--about-accent);
}

.page-about .rhythm-point {
  position: absolute;
  top: -0.5rem;
  left: 1.1rem;
  width: 10px;
  height: 10px;
  background: var(--about-accent);
  border-radius: 50%;
  transform: translateX(-50%);
}

.page-about .rhythm-point::after {
  content: "";
  position: absolute;
  inset: -4px;
  border: 1px solid var(--about-accent);
  border-radius: 50%;
  opacity: 0.6;
}

.page-about .rhythm-label {
  font-family: var(--about-mono);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--about-accent);
  letter-spacing: 0.06em;
}

.page-about .rhythm-text {
  font-size: 0.9rem;
  color: var(--about-muted);
  line-height: 1.6;
}

.page-about .rhythm-note {
  margin-top: 0.5rem;
}

.page-about .rhythm-figure {
  margin: 0;
  border: 2px solid var(--about-line-deep);
  background: var(--about-bg);
  padding: 0.75rem;
}

.page-about .manual-next {
  margin-top: clamp(2.5rem, 7vw, 4.5rem);
}

.page-about .next-panel {
  border: 3px solid var(--about-text);
  background: var(--about-surface);
  box-shadow: 10px 10px 0 rgba(0, 0, 0, 0.65);
  padding: clamp(1.5rem, 4vw, 3rem);
  position: relative;
}

.page-about .next-panel::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 6px;
  background: var(--about-accent);
}

.page-about .next-code {
  font-family: var(--about-mono);
  font-size: 0.8rem;
  letter-spacing: 0.16em;
  color: var(--about-accent);
}

.page-about .next-panel h2 {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 900;
  transform: skew(-4deg);
  transform-origin: left center;
  margin: 0.5rem 0 1rem;
}

.page-about .next-panel > p {
  color: var(--about-muted);
  line-height: 1.7;
  max-width: 40em;
  margin: 0 0 1.5rem;
}

.page-about .next-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}

.page-about .next-note {
  font-size: 0.875rem;
  color: var(--about-muted);
  margin: 0;
}

@media (min-width: 960px) {
  .page-about .cover-layout {
    grid-template-columns: minmax(0, 1fr) 320px;
    gap: 3rem;
  }

  .page-about .cover-sigil {
    justify-self: end;
  }

  .page-about .manual-toc {
    grid-template-columns: 200px 1fr;
  }

  .page-about .toc-list {
    grid-template-columns: 1fr 1fr;
  }

  .page-about .chapter-grid {
    grid-template-columns: minmax(0, 1fr) minmax(280px, 0.85fr);
  }

  .page-about .chapter-grid-boundary {
    grid-template-columns: minmax(0, 1.25fr) minmax(240px, 0.75fr);
  }

  .page-about .principle-list {
    grid-template-columns: 1fr;
  }

  .page-about .boundary-grid {
    grid-template-columns: 1fr 1fr;
  }

  .page-about .rhythm-timeline {
    grid-auto-columns: 1fr;
    overflow-x: visible;
    padding: 1.25rem;
  }
}

@media (min-width: 1240px) {
  .page-about .principle-item,
  .page-about .scenario-item {
    padding: 1.5rem;
  }

  .page-about .chapter-content {
    padding: clamp(1.5rem, 3vw, 2.75rem);
  }

  .page-about .rhythm-timeline {
    grid-auto-columns: 1fr;
  }
}