.page-about {
  --about-index-width: 220px;
  --about-timeline-width: 72px;
  position: relative;
  background: var(--color-bg);
  color: var(--color-text);
}

.page-about .about-hero {
  position: relative;
  overflow: hidden;
  padding: calc(var(--header-height) + 48px) 0 56px;
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  right: -80px;
  top: -80px;
  width: 340px;
  height: 340px;
  border-radius: 50%;
  border: 60px solid rgba(255, 196, 0, 0.05);
  pointer-events: none;
}

.page-about .about-hero-inner {
  position: relative;
  z-index: 1;
}

.page-about .about-breadcrumb {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
  margin-bottom: 32px;
}

.page-about .about-breadcrumb a {
  color: var(--color-text-secondary);
  text-decoration: none;
  transition: color 0.2s ease;
}

.page-about .about-breadcrumb a:hover {
  color: var(--color-yellow);
}

.page-about .about-breadcrumb span {
  margin: 0 6px;
  color: var(--color-text-muted);
}

.page-about .about-hero-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 36px;
}

.page-about .about-hero-media {
  position: relative;
  max-width: 420px;
  margin: 0 auto;
}

.page-about .about-hero-media::before {
  content: "";
  position: absolute;
  inset: 16px -12px -12px 16px;
  border: 2px solid var(--color-yellow);
  border-radius: var(--radius-lg);
  z-index: 0;
}

.page-about .about-hero-badge {
  position: relative;
  z-index: 1;
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-pop);
}

.page-about .about-hero-kicker {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-yellow);
  margin-bottom: 14px;
}

.page-about .about-hero-kicker::before {
  content: "";
  width: 24px;
  height: 2px;
  background: var(--color-yellow);
  flex-shrink: 0;
}

.page-about .about-hero h1 {
  font-family: var(--font-headline);
  font-size: clamp(36px, 7vw, 68px);
  line-height: 1.08;
  font-weight: 900;
  letter-spacing: -0.02em;
  margin: 0 0 16px;
}

.page-about .about-hero-lead {
  font-size: clamp(18px, 3vw, 26px);
  line-height: 1.5;
  font-weight: 700;
  color: var(--color-yellow);
  margin: 0 0 12px;
}

.page-about .about-hero-desc {
  font-size: 15px;
  line-height: 1.75;
  color: var(--color-text-secondary);
  max-width: 58ch;
  margin: 0 0 26px;
}

.page-about .about-index-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.page-about .about-index-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 14px;
  border: 1px solid var(--color-border);
  border-radius: 999px;
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: 13px;
  transition: border-color 0.2s ease, color 0.2s ease;
}

.page-about .about-index-link .about-index-num {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--color-yellow);
}

.page-about .about-index-link:hover {
  border-color: var(--color-yellow);
  color: var(--color-yellow);
}

.page-about .about-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: 40px;
  margin: 48px auto 0;
  position: relative;
}

.page-about .about-index-wrap {
  display: none;
}

.page-about .about-docs {
  position: relative;
  max-width: 850px;
}

.page-about .about-timeline {
  display: none;
}

.page-about .about-chapter {
  position: relative;
  padding: 52px 0 60px;
  border-bottom: 1px solid var(--color-border);
  scroll-margin-top: calc(var(--header-height) + 20px);
}

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

.page-about .about-chapter-head {
  display: flex;
  align-items: center;
  gap: 22px;
  margin-bottom: 28px;
  position: relative;
}

.page-about .about-chapter-num {
  font-family: var(--font-mono);
  font-size: 64px;
  font-weight: 700;
  line-height: 1;
  color: var(--color-yellow);
  opacity: 0.16;
  letter-spacing: -0.04em;
  min-width: 72px;
}

.page-about .about-chapter-tag {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--color-cyan);
  margin-bottom: 6px;
  text-transform: uppercase;
}

.page-about .about-chapter-head h2 {
  font-family: var(--font-headline);
  font-size: clamp(25px, 4vw, 36px);
  line-height: 1.15;
  font-weight: 900;
  margin: 0;
}

.page-about .about-chapter-body p {
  font-size: 15px;
  line-height: 1.8;
  color: var(--color-text-secondary);
  margin: 0 0 16px;
}

.page-about .about-chapter-body > p:first-of-type {
  color: var(--color-text);
  font-size: 16px;
}

.page-about .about-evolution {
  margin: 36px 0 8px;
  padding-left: 28px;
  position: relative;
}

.page-about .about-evo-line {
  position: absolute;
  left: 6px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: linear-gradient(to bottom, var(--color-yellow), var(--color-cyan) 60%, var(--color-orange));
}

.page-about .about-evo-item {
  position: relative;
  padding: 0 0 30px;
}

.page-about .about-evo-item:last-child {
  padding-bottom: 0;
}

.page-about .about-evo-dot {
  position: absolute;
  left: -27px;
  top: 7px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--color-yellow);
  box-shadow: 0 0 0 4px rgba(255, 196, 0, 0.14);
}

.page-about .about-evo-item:nth-child(3) .about-evo-dot {
  background: var(--color-cyan);
  box-shadow: 0 0 0 4px rgba(0, 212, 255, 0.14);
}

.page-about .about-evo-item:nth-child(4) .about-evo-dot {
  background: var(--color-orange);
  box-shadow: 0 0 0 4px rgba(255, 107, 0, 0.14);
}

.page-about .about-evo-item h3 {
  font-size: 17px;
  font-weight: 800;
  margin: 0 0 4px;
  color: var(--color-text);
}

.page-about .about-evo-item p {
  font-size: 14px;
  line-height: 1.6;
  color: var(--color-text-secondary);
  margin: 0;
}

.page-about .about-redesign-figure,
.page-about .about-service-figure {
  margin: 32px 0;
}

.page-about .about-redesign-figure img,
.page-about .about-service-figure img {
  width: 100%;
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-card);
}

.page-about .about-redesign-figure figcaption,
.page-about .about-service-figure figcaption {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
  color: var(--color-text-muted);
  margin-top: 12px;
}

.page-about .about-speed-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
  margin: 32px 0;
}

.page-about .about-speed-item {
  background: var(--color-panel);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 20px;
  transition: border-color 0.2s ease, transform 0.2s ease;
}

.page-about .about-speed-item:hover {
  border-color: var(--color-orange);
  transform: translateY(-2px);
}

.page-about .about-speed-icon {
  display: block;
  font-size: 22px;
  line-height: 1;
  margin-bottom: 10px;
  color: var(--color-yellow);
  font-family: var(--font-mono);
}

.page-about .about-speed-item strong {
  display: block;
  font-size: 16px;
  font-weight: 800;
  margin-bottom: 6px;
}

.page-about .about-speed-item p {
  font-size: 14px;
  line-height: 1.6;
  color: var(--color-text-secondary);
  margin: 0;
}

.page-about .about-version-wrap {
  display: grid;
  grid-template-columns: 1fr;
  gap: 22px;
  margin: 34px 0;
}

.page-about .about-version-card {
  position: relative;
  background: linear-gradient(135deg, var(--color-panel), var(--color-section));
  border: 1px solid var(--color-yellow);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-card);
}

.page-about .about-version-card-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
}

.page-about .about-version-label {
  font-size: 13px;
  letter-spacing: 0.04em;
  color: var(--color-text-secondary);
}

.page-about .about-version-code {
  font-family: var(--font-mono);
  font-size: 42px;
  line-height: 1;
  font-weight: 700;
  color: var(--color-yellow);
}

.page-about .about-version-hint {
  display: none;
}

.page-about .about-version-updates {
  border-top: 1px dashed var(--color-border);
  margin-top: 16px;
  padding-top: 16px;
}

.page-about .about-version-updates ul {
  margin: 8px 0 0;
  padding-left: 18px;
}

.page-about .about-version-updates li {
  font-size: 14px;
  line-height: 1.75;
  color: var(--color-text-secondary);
}

.page-about .about-version-desc {
  font-size: 14px;
  line-height: 1.75;
  color: var(--color-text-secondary);
  margin: 0;
}

.page-about .about-metrics {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
  margin: 34px 0;
}

.page-about .about-metric {
  background: var(--color-panel);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 24px 16px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.page-about .about-metric::after {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  height: 3px;
  width: 100%;
  background: linear-gradient(90deg, var(--color-yellow), var(--color-orange));
}

.page-about .about-metric[data-visible] {
  animation: about-rise 0.7s ease both;
}

@keyframes about-rise {
  from {
    opacity: 0.4;
    transform: translateY(18px);
  }
  to {
    opacity: 1;
    transform: none;
  }
}

.page-about .about-metric-value {
  font-family: var(--font-mono);
  font-size: clamp(40px, 7vw, 58px);
  font-weight: 700;
  line-height: 1;
  color: var(--color-yellow);
}

.page-about .about-metric-value .about-metric-unit {
  font-size: 0.45em;
  color: var(--color-cyan);
  margin-left: 2px;
}

.page-about .about-metric-label {
  display: block;
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--color-text-secondary);
  margin-top: 10px;
}

.page-about .about-service-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
  margin: 32px 0;
}

.page-about .about-service-card {
  background: transparent;
  border: 1px solid var(--color-border);
  border-top: 2px solid var(--color-yellow);
  border-radius: var(--radius-md);
  padding: 20px;
  transition: border-color 0.2s ease;
}

.page-about .about-service-card:hover {
  border-color: var(--color-yellow);
}

.page-about .about-service-card h3 {
  font-size: 16px;
  font-weight: 800;
  margin: 0 0 6px;
}

.page-about .about-service-card p {
  font-size: 14px;
  line-height: 1.65;
  color: var(--color-text-secondary);
  margin: 0;
}

.page-about .about-service-cta {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 32px;
  padding: 22px;
  background: var(--color-section);
  border-radius: var(--radius-md);
}

.page-about .about-chapter-link {
  margin-top: 22px;
}

.page-about .btn.btn-outline {
  text-decoration: none;
}

@media (min-width: 768px) {
  .page-about .about-hero-grid {
    grid-template-columns: 400px 1fr;
    align-items: center;
    gap: 56px;
  }

  .page-about .about-hero-copy {
    padding-top: 8px;
  }

  .page-about .about-speed-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .page-about .about-metrics {
    grid-template-columns: repeat(3, 1fr);
  }

  .page-about .about-service-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .page-about .about-version-wrap {
    grid-template-columns: 320px 1fr;
    align-items: start;
  }

  .page-about .about-version-hint {
    display: block;
    font-family: var(--font-mono);
    font-size: 12px;
    color: var(--color-text-muted);
    margin: 14px 0 0;
  }

  .page-about .about-version-updates {
    max-height: 0;
    opacity: 0;
    overflow: hidden;
    margin-top: 0;
    padding-top: 0;
    border-top: 0;
    transition: max-height 0.35s ease, opacity 0.25s ease, margin-top 0.3s ease, padding-top 0.3s ease;
  }

  .page-about .about-version-card:hover .about-version-updates,
  .page-about .about-version-card:focus-within .about-version-updates,
  .page-about .about-version-card:focus .about-version-updates {
    max-height: 280px;
    opacity: 1;
    margin-top: 16px;
    padding-top: 16px;
    border-top: 1px dashed var(--color-border);
  }

  .page-about .about-evolution {
    padding-left: 34px;
  }
}

@media (min-width: 1080px) {
  .page-about .about-layout {
    grid-template-columns: var(--about-index-width) 1fr;
    gap: 76px;
  }

  .page-about .about-index-wrap {
    display: block;
    position: sticky;
    top: calc(var(--header-height) + 24px);
    align-self: start;
  }

  .page-about .about-side-index {
    border-left: 2px solid var(--color-border);
    padding-left: 22px;
  }

  .page-about .about-side-link {
    display: flex;
    gap: 12px;
    align-items: baseline;
    padding: 12px 0;
    text-decoration: none;
    color: var(--color-text-secondary);
    font-size: 14px;
    border-bottom: 1px solid var(--color-border);
    transition: color 0.2s ease, border-color 0.2s ease;
  }

  .page-about .about-side-link span {
    font-family: var(--font-mono);
    font-size: 12px;
    color: var(--color-yellow);
  }

  .page-about .about-side-link:hover {
    color: var(--color-yellow);
    border-color: var(--color-yellow);
  }

  .page-about .about-timeline {
    display: block;
    position: absolute;
    left: -76px;
    top: 0;
    bottom: 0;
    width: var(--about-timeline-width);
    pointer-events: none;
    z-index: 1;
  }

  .page-about .about-timeline-svg {
    display: block;
    width: 100%;
    height: 100%;
  }

  .page-about .about-timeline-dot {
    position: absolute;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: var(--color-yellow);
    box-shadow: 0 0 0 4px rgba(255, 196, 0, 0.18);
  }

  .page-about .about-timeline-dot:nth-of-type(1) {
    top: 4.4%;
    background: var(--color-yellow);
    box-shadow: 0 0 0 4px rgba(255, 196, 0, 0.18);
  }

  .page-about .about-timeline-dot:nth-of-type(2) {
    top: 33.3%;
    background: var(--color-cyan);
    box-shadow: 0 0 0 4px rgba(0, 212, 255, 0.18);
  }

  .page-about .about-timeline-dot:nth-of-type(3) {
    top: 62.2%;
    background: var(--color-orange);
    box-shadow: 0 0 0 4px rgba(255, 107, 0, 0.18);
  }

  .page-about .about-timeline-dot:nth-of-type(4) {
    top: 88.9%;
    background: var(--color-yellow);
    box-shadow: 0 0 0 4px rgba(255, 196, 0, 0.18);
  }

  .page-about .about-chapter {
    padding: 64px 0 72px;
  }

  .page-about .about-chapter-num {
    font-size: 88px;
    min-width: 104px;
  }

  .page-about .about-chapter-body {
    max-width: 70ch;
  }

  .page-about .about-chapter-body p {
    font-size: 16px;
  }
}