.page-about {
  --about-bg-brand: rgba(46, 125, 50, 0.06);
  --about-bg-archive: rgba(26, 35, 126, 0.05);
  --about-bg-support: rgba(255, 193, 7, 0.08);
  --about-number-size: 4.5rem;
  --about-number-color: var(--color-primary);
  --about-hero-gap: 2rem;
  --about-section-radius: 24px;
  --about-section-padding: 2rem 1.5rem;
}

/* ---- 移动端优先 ---- */
.page-about .breadcrumb {
  padding: 1rem 1.25rem 0;
  font-family: var(--font-body);
  font-size: var(--size-sm);
  color: var(--color-text-secondary);
  max-width: var(--max-width);
  margin: 0 auto;
}
.page-about .breadcrumb a {
  color: var(--color-primary);
  text-decoration: none;
}
.page-about .breadcrumb a:hover {
  text-decoration: underline;
}
.page-about .breadcrumb-sep {
  margin: 0 0.35rem;
  color: var(--color-border);
}
.page-about .breadcrumb-current {
  color: var(--color-text-secondary);
}

/* ---- 首屏 ---- */
.page-about .about-hero {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  padding: 1.5rem 1.25rem 2.5rem;
  max-width: var(--max-width);
  margin: 0 auto;
}
.page-about .about-hero-image {
  order: 0;
  width: 100%;
  max-width: 400px;
  margin: 0 auto;
}
.page-about .about-hero-image img {
  display: block;
  width: 100%;
  height: auto;
  max-width: 100%;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  object-fit: cover;
  aspect-ratio: 1 / 1;
}
.page-about .about-hero-text {
  order: 1;
  position: relative;
}
.page-about .about-hero-text .rotated-note {
  display: inline-block;
  writing-mode: vertical-rl;
  font-family: var(--font-heading);
  font-size: var(--size-xs);
  letter-spacing: 0.15em;
  color: var(--color-secondary);
  position: absolute;
  left: -0.5rem;
  top: 0.25rem;
  opacity: 0.7;
  pointer-events: none;
}
.page-about .about-hero-text h1 {
  font-family: var(--font-heading);
  font-size: var(--size-3xl);
  font-weight: 900;
  line-height: 1.1;
  color: var(--color-primary);
  margin: 0 0 0.75rem 0.75rem;
  letter-spacing: 0.02em;
}
.page-about .about-lead {
  font-family: var(--font-body);
  font-size: var(--size-md);
  line-height: 1.6;
  color: var(--color-text);
  max-width: 480px;
  margin: 0 0 0 0.75rem;
}

/* ---- 章节导航 ---- */
.page-about .about-chapter-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1.25rem;
  padding: 1.25rem;
  max-width: var(--max-width);
  margin: 0 auto 1.5rem;
  border-top: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
}
.page-about .chapter-link {
  font-family: var(--font-body);
  font-size: var(--size-sm);
  font-weight: 600;
  color: var(--color-text-secondary);
  text-decoration: none;
  padding: 0.25rem 0;
  transition: color var(--transition-fast);
  display: inline-flex;
  align-items: baseline;
  gap: 0.35rem;
}
.page-about .chapter-link:hover,
.page-about .chapter-link:focus {
  color: var(--color-primary);
}
.page-about .chapter-num {
  font-family: var(--font-heading);
  font-size: var(--size-xs);
  color: var(--color-primary);
  opacity: 0.6;
}

/* ---- 通用章节 ---- */
.page-about .about-section {
  max-width: var(--max-width);
  margin: 0 auto 1.5rem;
  padding: 0 1.25rem;
}
.page-about .section-inner {
  background: var(--color-bg-light);
  border-radius: var(--about-section-radius);
  padding: var(--about-section-padding);
  position: relative;
  overflow: hidden;
}
.page-about .section-brand .section-inner {
  background: var(--about-bg-brand);
}
.page-about .section-archive .section-inner {
  background: var(--about-bg-archive);
}
.page-about .section-support .section-inner {
  background: var(--about-bg-support);
}

.page-about .section-number {
  font-family: var(--font-heading);
  font-size: var(--about-number-size);
  font-weight: 900;
  line-height: 1;
  color: var(--about-number-color);
  opacity: 0.12;
  position: absolute;
  top: -0.3rem;
  right: 0.5rem;
  pointer-events: none;
  user-select: none;
}
.page-about .section-title {
  font-family: var(--font-heading);
  font-size: var(--size-xl);
  font-weight: 900;
  line-height: 1.15;
  color: var(--color-text);
  margin: 0 0 1rem;
  position: relative;
  z-index: 1;
}
.page-about .section-body {
  font-family: var(--font-body);
  font-size: var(--size-base);
  line-height: 1.65;
  color: var(--color-text);
  position: relative;
  z-index: 1;
}
.page-about .section-body p {
  margin: 0 0 0.75rem;
}
.page-about .section-body p:last-child {
  margin-bottom: 0;
}

/* ---- details 展开收起 ---- */
.page-about .about-details {
  margin-top: 1rem;
  font-size: var(--size-sm);
  color: var(--color-text-secondary);
}
.page-about .about-details summary {
  cursor: pointer;
  font-weight: 600;
  color: var(--color-primary);
  padding: 0.25rem 0;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  transition: color var(--transition-fast);
}
.page-about .about-details summary:hover {
  color: var(--color-primary-dark);
}
.page-about .about-details summary::marker {
  content: "▸ ";
  color: var(--color-secondary);
}
.page-about .about-details[open] summary::marker {
  content: "▾ ";
}
.page-about .about-details p {
  margin: 0.75rem 0 0;
  padding-left: 0.5rem;
  border-left: 2px solid var(--color-secondary);
}

/* ---- 资料收录配图 ---- */
.page-about .section-image {
  margin-top: 1.25rem;
  position: relative;
  z-index: 1;
}
.page-about .section-image img {
  display: block;
  width: 100%;
  max-width: 300px;
  height: auto;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  object-fit: cover;
  aspect-ratio: 3 / 2;
}

/* ---- 技术支持图标 ---- */
.page-about .section-icon {
  margin-top: 1.25rem;
  position: relative;
  z-index: 1;
}
.page-about .section-icon img {
  display: block;
  width: 80px;
  height: 80px;
  max-width: 100%;
  border-radius: var(--radius-md);
  object-fit: contain;
  background: var(--color-white);
  padding: 0.5rem;
  box-shadow: var(--shadow-sm);
}

/* ---- 相关链接 ---- */
.page-about .about-related {
  max-width: var(--max-width);
  margin: 2rem auto 0;
  padding: 2rem 1.25rem 3rem;
  border-top: 1px solid var(--color-border);
}
.page-about .related-heading {
  font-family: var(--font-heading);
  font-size: var(--size-lg);
  font-weight: 900;
  color: var(--color-text);
  margin: 0 0 1rem;
}
.page-about .related-links {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem 1.5rem;
}
.page-about .related-link {
  font-family: var(--font-body);
  font-size: var(--size-base);
  font-weight: 600;
  color: var(--color-primary);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  transition: color var(--transition-fast), gap var(--transition-fast);
}
.page-about .related-link:hover,
.page-about .related-link:focus {
  color: var(--color-primary-dark);
  gap: 0.6rem;
}
.page-about .link-arrow {
  font-size: var(--size-md);
  transition: transform var(--transition-fast);
}
.page-about .related-link:hover .link-arrow {
  transform: translateX(3px);
}

/* ---- 桌面端 >= 768px ---- */
@media (min-width: 768px) {
  .page-about .breadcrumb {
    padding: 1.5rem 2rem 0;
  }

  .page-about .about-hero {
    flex-direction: row;
    align-items: center;
    gap: var(--about-hero-gap);
    padding: 2rem 2rem 3.5rem;
  }
  .page-about .about-hero-image {
    order: 0;
    flex: 0 0 45%;
    max-width: 480px;
    margin: 0;
  }
  .page-about .about-hero-text {
    order: 1;
    flex: 1 1 55%;
    padding-left: 0.75rem;
  }
  .page-about .about-hero-text .rotated-note {
    left: -1.25rem;
    top: 0.5rem;
    font-size: var(--size-sm);
  }
  .page-about .about-hero-text h1 {
    font-size: var(--size-4xl);
    margin-left: 0.5rem;
  }
  .page-about .about-lead {
    font-size: var(--size-lg);
    margin-left: 0.5rem;
  }

  .page-about .about-chapter-nav {
    padding: 1.5rem 2rem;
    gap: 0.75rem 2.5rem;
    margin-bottom: 2.5rem;
  }
  .page-about .chapter-link {
    font-size: var(--size-base);
  }

  .page-about .about-section {
    padding: 0 2rem;
    margin-bottom: 2rem;
  }
  .page-about .section-inner {
    padding: 3rem 2.5rem;
  }
  .page-about .section-number {
    font-size: 6rem;
    top: -0.5rem;
    right: 1rem;
  }
  .page-about .section-title {
    font-size: var(--size-2xl);
    margin-bottom: 1.25rem;
  }
  .page-about .section-body {
    font-size: var(--size-md);
  }

  .page-about .section-archive .section-inner {
    display: grid;
    grid-template-columns: 1fr 300px;
    gap: 1.5rem 2rem;
    align-items: start;
  }
  .page-about .section-archive .section-number {
    grid-column: 1 / -1;
  }
  .page-about .section-archive .section-title {
    grid-column: 1;
    grid-row: 2;
  }
  .page-about .section-archive .section-body {
    grid-column: 1;
    grid-row: 3;
  }
  .page-about .section-archive .section-image {
    grid-column: 2;
    grid-row: 2 / 4;
    margin-top: 0;
  }
  .page-about .section-archive .section-image img {
    max-width: 100%;
    aspect-ratio: 3 / 2;
  }

  .page-about .section-support .section-inner {
    display: grid;
    grid-template-columns: 1fr 120px;
    gap: 1rem 2rem;
    align-items: start;
  }
  .page-about .section-support .section-number {
    grid-column: 1 / -1;
  }
  .page-about .section-support .section-title {
    grid-column: 1;
    grid-row: 2;
  }
  .page-about .section-support .section-body {
    grid-column: 1;
    grid-row: 3;
  }
  .page-about .section-support .section-icon {
    grid-column: 2;
    grid-row: 2 / 4;
    margin-top: 0;
    justify-self: center;
  }
  .page-about .section-support .section-icon img {
    width: 100px;
    height: 100px;
  }

  .page-about .about-related {
    padding: 2.5rem 2rem 4rem;
  }
  .page-about .related-heading {
    font-size: var(--size-xl);
  }
  .page-about .related-links {
    gap: 1rem 2rem;
  }
}

/* ---- 桌面端 >= 1024px ---- */
@media (min-width: 1024px) {
  .page-about .about-hero {
    padding: 2.5rem 2rem 4rem;
    gap: 3rem;
  }
  .page-about .about-hero-image {
    flex: 0 0 40%;
    max-width: 520px;
  }
  .page-about .about-hero-text h1 {
    font-size: 3.5rem;
  }
  .page-about .about-lead {
    font-size: var(--size-xl);
    max-width: 520px;
  }

  .page-about .section-inner {
    padding: 3.5rem 3rem;
  }
  .page-about .section-number {
    font-size: 7rem;
  }
  .page-about .section-title {
    font-size: var(--size-3xl);
  }
}