.page-about {
  --about-index-w: clamp(180px, 28%, 260px);
  --about-gap: 2rem;
  --about-radius: var(--radius-md, 8px);
  --about-section-shadow: 0 2px 12px rgba(0,0,0,0.04);
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  color: var(--color-dark, #2B2D42);
  max-width: var(--content-max, 1280px);
  margin: 0 auto;
  padding: 1.5rem 1rem 3rem;
}
.page-about .about-grid {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}
.page-about .about-index {
  order: 0;
  width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: thin;
}
.page-about .about-index::-webkit-scrollbar {
  height: 4px;
  background: var(--color-light, #F1FAEE);
}
.page-about .about-index::-webkit-scrollbar-thumb {
  background: var(--color-red, #E63946);
  border-radius: 4px;
}
.page-about .about-index-nav {
  display: flex;
  flex-direction: row;
  gap: 0.5rem;
  padding: 0.25rem 0;
  min-width: max-content;
}
.page-about .about-index-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.6rem 1.2rem;
  background: var(--color-light, #F1FAEE);
  border-radius: var(--about-radius);
  text-decoration: none;
  transition: background var(--transition, 0.28s ease), color var(--transition, 0.28s ease);
  white-space: nowrap;
}
.page-about .about-index-item:hover,
.page-about .about-index-item:focus {
  background: rgba(230,57,70,0.08);
}
.page-about .about-index-item .index-number {
  font-family: var(--font-number, 'JetBrains Mono', monospace);
  font-weight: 600;
  font-size: 1.25rem;
  color: var(--color-red, #E63946);
  line-height: 1;
  transition: color var(--transition, 0.28s ease);
}
.page-about .about-index-item .index-title {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--color-blue, #1D3557);
  line-height: 1.3;
  transition: color var(--transition, 0.28s ease);
}
.page-about .about-index-item:hover .index-title,
.page-about .about-index-item:focus .index-title {
  color: var(--color-red, #E63946);
}
.page-about .about-content {
  order: 1;
  flex: 1;
  min-width: 0;
}
.page-about .about-content-header {
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 2px solid var(--color-light, #F1FAEE);
}
.page-about .about-breadcrumb {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.8rem;
  color: var(--color-dark, #2B2D42);
  opacity: 0.65;
  margin-bottom: 0.6rem;
}
.page-about .about-breadcrumb a {
  color: var(--color-blue, #1D3557);
  text-decoration: none;
  transition: color var(--transition, 0.28s ease);
}
.page-about .about-breadcrumb a:hover {
  color: var(--color-red, #E63946);
}
.page-about .breadcrumb-sep {
  color: var(--color-gold, #F4A261);
  font-weight: 600;
}
.page-about .about-page-title {
  font-family: 'Inter', system-ui, sans-serif;
  font-weight: 700;
  font-style: italic;
  font-size: 1.75rem;
  color: var(--color-blue, #1D3557);
  margin: 0 0 0.25rem;
  line-height: 1.2;
}
.page-about .about-page-desc {
  font-size: 0.95rem;
  color: var(--color-dark, #2B2D42);
  opacity: 0.7;
  margin: 0;
}
.page-about .about-section {
  background: var(--color-white, #FFFFFF);
  border-radius: var(--about-radius);
  box-shadow: var(--about-section-shadow);
  margin-bottom: 1rem;
  overflow: hidden;
  border: 1px solid rgba(0,0,0,0.04);
  transition: box-shadow var(--transition, 0.28s ease);
}
.page-about .about-section[open] {
  box-shadow: 0 4px 20px rgba(0,0,0,0.06);
}
.page-about .about-section summary {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 1rem 1.25rem;
  background: var(--color-blue, #1D3557);
  color: var(--color-white, #FFFFFF);
  font-weight: 600;
  font-size: 1.1rem;
  cursor: pointer;
  list-style: none;
  transition: background var(--transition, 0.28s ease);
  position: relative;
  user-select: none;
}
.page-about .about-section summary::-webkit-details-marker {
  display: none;
}
.page-about .about-section summary::after {
  content: '';
  width: 0.7rem;
  height: 0.7rem;
  border-right: 2px solid var(--color-gold, #F4A261);
  border-bottom: 2px solid var(--color-gold, #F4A261);
  transform: rotate(-45deg);
  margin-left: auto;
  transition: transform var(--transition, 0.28s ease);
  flex-shrink: 0;
}
.page-about .about-section[open] summary::after {
  transform: rotate(45deg);
}
.page-about .about-section summary:hover {
  background: #162945;
}
.page-about .section-summary-number {
  font-family: var(--font-number, 'JetBrains Mono', monospace);
  font-weight: 700;
  font-size: 1.3rem;
  color: var(--color-gold, #F4A261);
  line-height: 1;
  margin-right: 0.2rem;
}
.page-about .about-section-body {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  padding: 1.5rem 1.25rem;
  background: var(--color-light, #F1FAEE);
}
.page-about .section-text {
  flex: 1;
  min-width: 0;
}
.page-about .section-text p {
  margin: 0 0 0.75rem;
  font-size: 1rem;
  line-height: 1.65;
  color: var(--color-dark, #2B2D42);
}
.page-about .section-text p:last-child {
  margin-bottom: 0;
}
.page-about .highlight-red {
  color: var(--color-red, #E63946);
  font-weight: 600;
}
.page-about .section-figure {
  margin: 0;
  flex-shrink: 0;
}
.page-about .section-img {
  display: block;
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-sm, 4px);
  object-fit: cover;
  background: var(--color-light, #F1FAEE);
}
.page-about .icon-figure {
  align-self: flex-start;
}
.page-about .icon-img {
  display: block;
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-sm, 4px);
  object-fit: contain;
}
.page-about .feature-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}
.page-about .feature-list li {
  padding: 0.75rem 1rem;
  background: var(--color-white, #FFFFFF);
  border-radius: var(--radius-sm, 4px);
  border-left: 3px solid var(--color-red, #E63946);
  font-size: 0.95rem;
  line-height: 1.5;
  color: var(--color-dark, #2B2D42);
}
.page-about .feature-list li strong {
  color: var(--color-blue, #1D3557);
  font-weight: 600;
}
.page-about .contact-info {
  flex: 1;
  min-width: 0;
}
.page-about .contact-info p {
  margin: 0 0 0.6rem;
  font-size: 0.95rem;
  line-height: 1.6;
  color: var(--color-dark, #2B2D42);
}
.page-about .contact-info strong {
  color: var(--color-blue, #1D3557);
  font-weight: 600;
}
.page-about .contact-email {
  font-family: var(--font-number, 'JetBrains Mono', monospace);
  color: var(--color-red, #E63946);
  cursor: pointer;
  border-bottom: 1px dashed var(--color-red, #E63946);
  transition: opacity var(--transition, 0.28s ease);
}
.page-about .contact-email:hover {
  opacity: 0.75;
}
.page-about .contact-note {
  font-size: 0.875rem;
  color: var(--color-dark, #2B2D42);
  opacity: 0.75;
  margin-top: 0.5rem;
  padding-top: 0.5rem;
  border-top: 1px solid rgba(0,0,0,0.06);
}
.page-about .contact-link {
  display: inline-block;
  margin-top: 0.75rem;
  padding: 0.5rem 1.25rem;
  font-size: 0.9rem;
  border: 1px solid var(--color-blue, #1D3557);
  color: var(--color-blue, #1D3557);
  background: transparent;
  border-radius: var(--radius-sm, 4px);
  text-decoration: none;
  transition: background var(--transition, 0.28s ease), color var(--transition, 0.28s ease);
}
.page-about .contact-link:hover {
  background: var(--color-blue, #1D3557);
  color: var(--color-white, #FFFFFF);
}
.page-about .contact-figure {
  max-width: 300px;
}

@media (min-width: 768px) {
  .page-about {
    padding: 2rem 1.5rem 4rem;
  }
  .page-about .about-grid {
    flex-direction: row;
    align-items: flex-start;
    gap: var(--about-gap, 2rem);
  }
  .page-about .about-index {
    order: 0;
    width: var(--about-index-w);
    flex-shrink: 0;
    position: sticky;
    top: calc(var(--header-h, 56px) + 1.5rem);
    max-height: calc(100vh - var(--header-h, 56px) - 3rem);
    overflow-y: auto;
    overflow-x: visible;
    scrollbar-width: thin;
  }
  .page-about .about-index-nav {
    flex-direction: column;
    gap: 0.35rem;
    padding: 0.5rem 0.5rem 0.5rem 0;
    min-width: 0;
  }
  .page-about .about-index-item {
    padding: 0.65rem 1rem;
    background: transparent;
    border-radius: var(--radius-sm, 4px);
    border-left: 3px solid transparent;
    white-space: normal;
  }
  .page-about .about-index-item:hover,
  .page-about .about-index-item:focus {
    background: rgba(230,57,70,0.05);
    border-left-color: var(--color-red, #E63946);
  }
  .page-about .about-index-item .index-number {
    font-size: 1.4rem;
  }
  .page-about .about-index-item .index-title {
    font-size: 0.9rem;
  }
  .page-about .about-content {
    order: 1;
    flex: 1;
    min-width: 0;
  }
  .page-about .about-page-title {
    font-size: 2.25rem;
  }
  .page-about .about-section-body {
    flex-direction: row;
    align-items: flex-start;
  }
  .page-about .about-section-body .section-text {
    flex: 1;
  }
  .page-about .about-section-body .section-figure {
    max-width: 50%;
  }
  .page-about .contact-figure {
    max-width: 280px;
  }
}

@media (min-width: 1024px) {
  .page-about {
    padding: 2.5rem 2rem 5rem;
  }
  .page-about .about-page-title {
    font-size: 2.75rem;
  }
  .page-about .about-index-item .index-number {
    font-size: 1.6rem;
  }
}