.page-about {
  --about-paper-line: rgba(10, 25, 47, 0.05);
  --about-paper-rule: rgba(10, 25, 47, 0.1);
  position: relative;
  color: var(--c-paper);
  background:
    radial-gradient(90% 320px at 88% 8%, rgba(75, 108, 183, 0.34), transparent 60%),
    radial-gradient(70% 200px at 6% 20%, rgba(255, 215, 0, 0.1), transparent 50%),
    linear-gradient(180deg, var(--c-bg) 0%, var(--c-bg-deep) 100%);
}

.page-about .about-board {
  padding: 24px 0 96px;
}

.page-about .about-breadcrumb {
  margin-bottom: 32px;
  font-size: 14px;
  color: var(--c-gray);
}

.page-about .about-breadcrumb a {
  color: var(--c-paper);
  text-decoration: none;
}

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

.page-about .about-breadcrumb .sep {
  margin: 0 8px;
  color: var(--c-gold);
}

.page-about .about-hero {
  position: relative;
  padding: 24px 0 56px;
  border-bottom: 1px solid rgba(168, 178, 209, 0.22);
}

.page-about .about-hero-kicker {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 28px;
  font-size: 14px;
  letter-spacing: 0.08em;
  color: var(--c-gold);
}

.page-about .about-title {
  margin: 0;
  max-width: 900px;
  font-size: clamp(46px, 9vw, 88px);
  font-weight: 900;
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--c-paper);
}

.page-about .about-hero-desc {
  max-width: 680px;
  margin: 22px 0 0;
  font-size: 17px;
  line-height: 1.8;
  color: var(--c-gray);
}

.page-about .about-hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 28px;
  margin-top: 40px;
  padding-top: 24px;
  border-top: 1px solid rgba(168, 178, 209, 0.24);
}

.page-about .hero-meta-item {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.page-about .hero-meta-num {
  font-size: 30px;
  font-weight: 900;
  color: var(--c-gold);
  letter-spacing: -0.02em;
}

.page-about .hero-meta-label {
  font-size: 13px;
  color: var(--c-gray);
  letter-spacing: 0.04em;
}

.page-about .about-hero-line {
  position: absolute;
  left: 0;
  bottom: -1px;
  width: 33.333%;
  height: 3px;
  background: linear-gradient(90deg, var(--c-gold), var(--c-gold-soft), transparent);
}

.page-about .about-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: 32px;
  margin-top: 40px;
}

.page-about .about-sidebar {
  order: 2;
}

.page-about .about-content {
  order: 1;
}

.page-about .panel-side {
  background: rgba(11, 19, 43, 0.72);
  border: 1px solid var(--c-border);
  border-top: 3px solid var(--c-gold);
  border-radius: 2px;
  padding: 20px;
  margin-bottom: 20px;
  -webkit-backdrop-filter: blur(6px);
  backdrop-filter: blur(6px);
}

.page-about .sidebar-title {
  margin: 0 0 16px;
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--c-gold);
  text-transform: uppercase;
}

.page-about .sidebar-list {
  list-style: none;
  counter-reset: sidx;
  margin: 0;
  padding: 0;
}

.page-about .sidebar-list li {
  counter-increment: sidx;
  border-bottom: 1px dashed rgba(168, 178, 209, 0.2);
  padding: 10px 0;
}

.page-about .sidebar-list li:last-child {
  border-bottom: none;
}

.page-about .sidebar-list a {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 15px;
  color: var(--c-paper);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.page-about .sidebar-list a::before {
  content: counter(sidx, decimal-leading-zero);
  font-size: 12px;
  font-weight: 700;
  color: var(--c-gold);
}

.page-about .sidebar-list a:hover {
  color: var(--c-gold);
}

.page-about .glossary-list {
  margin: 0;
  padding: 0;
}

.page-about .glossary-item {
  padding: 8px 0;
  border-bottom: 1px dashed rgba(168, 178, 209, 0.2);
}

.page-about .glossary-item:last-child {
  border-bottom: none;
}

.page-about .glossary-item dt {
  font-weight: 700;
  font-size: 15px;
  color: var(--c-paper);
}

.page-about .glossary-item dd {
  margin: 4px 0 0;
  font-size: 13px;
  line-height: 1.6;
  color: var(--c-gray);
}

.page-about .reading-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .reading-list li a {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 8px 0;
  border-bottom: 1px dashed rgba(168, 178, 209, 0.2);
  font-size: 14px;
  color: var(--c-paper);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.page-about .reading-list li:last-child a {
  border-bottom: none;
}

.page-about .reading-list li a::after {
  content: "→";
  color: var(--c-gold);
}

.page-about .reading-list li a:hover {
  color: var(--c-gold);
}

.page-about .section-block {
  position: relative;
  margin-bottom: 32px;
  padding: 28px 24px 32px;
  border-radius: 3px;
  background-color: var(--c-paper);
  background-image: linear-gradient(var(--about-paper-line) 1px, transparent 1px);
  background-size: 100% 28px;
  color: var(--c-bg);
  box-shadow: 0 20px 48px rgba(0, 0, 0, 0.34);
  scroll-margin-top: calc(var(--header-height) + 20px);
  border: 1px solid rgba(10, 25, 47, 0.08);
}

.page-about .section-block::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--c-gold) 0%, var(--c-gold-soft) 60%, transparent 100%);
}

.page-about .section-block::after {
  content: "";
  position: absolute;
  top: 12px;
  right: 16px;
  width: 18px;
  height: 5px;
  border-radius: 1px;
  background: var(--c-gold-soft);
  opacity: 0.3;
}

.page-about .section-head {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  margin-bottom: 28px;
  padding-right: 40px;
}

.page-about .section-index {
  min-width: 72px;
  font-size: clamp(48px, 7vw, 64px);
  font-weight: 900;
  line-height: 1;
  letter-spacing: -0.04em;
  color: rgba(10, 25, 47, 0.12);
}

.page-about .section-head-text .index-label {
  display: block;
  margin-bottom: 6px;
}

.page-about .section-head h2 {
  margin: 0;
  font-size: clamp(26px, 4vw, 32px);
  font-weight: 900;
  letter-spacing: -0.01em;
  color: var(--c-bg);
}

.page-about .section-intro {
  margin: -8px 0 28px;
  font-size: 15px;
  line-height: 1.75;
  color: #334155;
}

.page-about .story-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: 24px;
  margin-bottom: 28px;
}

.page-about .story-copy p {
  margin: 0 0 16px;
  font-size: 15px;
  line-height: 1.85;
  color: #233450;
}

.page-about .story-commitment {
  align-self: start;
  padding: 20px 20px 18px;
  border-left: 4px solid var(--c-gold);
  background: linear-gradient(135deg, rgba(75, 108, 183, 0.1), rgba(255, 215, 0, 0.08));
}

.page-about .story-commitment p {
  margin: 0 0 12px;
  font-size: 15px;
  font-weight: 700;
  line-height: 1.75;
  color: var(--c-bg);
}

.page-about .commitment-mark {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--c-gold-soft);
}

.page-about .story-visual {
  margin: 0;
}

.page-about .story-visual img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 3px;
  border: 1px solid var(--about-paper-rule);
}

.page-about .story-visual figcaption,
.page-about .data-figure figcaption,
.page-about .coverage-visual figcaption {
  margin-top: 10px;
  padding-left: 16px;
  border-left: 2px solid var(--c-gold);
  font-size: 13px;
  color: var(--c-gray);
}

.page-about .milestone-scroll {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  padding-bottom: 16px;
  scrollbar-width: thin;
  scrollbar-color: var(--c-gold) transparent;
}

.page-about .milestone-track {
  display: flex;
  gap: 16px;
  min-width: 840px;
  padding-top: 8px;
}

.page-about .milestone-card {
  position: relative;
  flex: 0 0 240px;
  padding: 24px 20px 18px;
  border-radius: 3px;
  border-top: 4px solid var(--c-gold);
  background: linear-gradient(135deg, var(--c-bg) 0%, var(--c-bg-deep) 100%);
  color: var(--c-paper);
  box-shadow: 0 10px 24px rgba(10, 25, 47, 0.22);
  cursor: default;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.page-about .milestone-card:hover,
.page-about .milestone-card:focus {
  transform: translateY(-6px);
  box-shadow: 0 16px 28px rgba(10, 25, 47, 0.32);
}

.page-about .milestone-card:focus-visible {
  outline: 2px solid var(--c-gold);
  outline-offset: 3px;
}

.page-about .milestone-year {
  display: block;
  font-size: 42px;
  font-weight: 900;
  line-height: 1;
  letter-spacing: -0.03em;
  color: var(--c-gold);
}

.page-about .milestone-card h3 {
  margin: 14px 0 4px;
  font-size: 18px;
  font-weight: 700;
  color: var(--c-paper);
}

.page-about .milestone-tag {
  font-size: 12px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--c-gray);
}

.page-about .milestone-card-detail {
  max-height: 0;
  opacity: 0;
  overflow: hidden;
  transition: max-height 0.32s var(--ease-out), opacity 0.32s var(--ease-out), padding-top 0.32s var(--ease-out);
}

.page-about .milestone-card-detail p {
  margin: 0;
  padding-top: 14px;
  border-top: 1px solid rgba(168, 178, 209, 0.2);
  font-size: 14px;
  line-height: 1.7;
  color: var(--c-gray);
}

.page-about .milestone-card:hover .milestone-card-detail,
.page-about .milestone-card:focus .milestone-card-detail,
.page-about .milestone-card:focus-within .milestone-card-detail {
  max-height: 300px;
  opacity: 1;
  padding-top: 14px;
}

.page-about .milestone-scroll-hint {
  display: inline-block;
  margin-top: 4px;
  font-size: 12px;
  color: var(--c-gray);
}

.page-about .data-stats {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin-bottom: 32px;
}

.page-about .stat-item {
  padding: 20px 16px;
  border: 1px solid rgba(10, 25, 47, 0.1);
  border-bottom: 3px solid var(--c-gold);
  background: linear-gradient(160deg, #f1faee 0%, #e7ecf5 100%);
}

.page-about .stat-num {
  display: block;
  font-size: clamp(34px, 6vw, 44px);
  font-weight: 900;
  line-height: 1.05;
  letter-spacing: -0.03em;
  color: var(--c-bg);
}

.page-about .stat-plus,
.page-about .stat-unit {
  font-size: 20px;
  font-weight: 900;
  color: var(--c-gold-soft);
}

.page-about .stat-label {
  display: block;
  margin-top: 8px;
  font-size: 14px;
  font-weight: 500;
  color: #3e5c8a;
}

.page-about .data-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: 28px;
}

.page-about .data-figure {
  margin: 0;
}

.page-about .data-figure img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 3px;
  border: 1px solid rgba(10, 25, 47, 0.1);
}

.page-about .data-note {
  padding: 24px;
  border-radius: 3px;
  background: linear-gradient(160deg, var(--c-bg) 0%, var(--c-bg-deep) 100%);
  color: var(--c-paper);
  align-self: start;
}

.page-about .data-note h3 {
  margin: 0 0 12px;
  font-size: 20px;
  font-weight: 700;
  color: var(--c-gold);
}

.page-about .data-note p {
  margin: 0 0 12px;
  font-size: 14px;
  line-height: 1.8;
  color: var(--c-gray);
}

.page-about .data-note-rule {
  height: 1px;
  margin: 20px 0;
  background: linear-gradient(90deg, var(--c-gold), transparent);
}

.page-about .data-note p.data-update-line {
  margin-bottom: 0;
  font-size: 14px;
  font-weight: 700;
  color: var(--c-paper);
}

.page-about .coverage-visual {
  margin: 0 0 28px;
}

.page-about .coverage-visual img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 3px;
  border: 1px solid rgba(10, 25, 47, 0.1);
}

.page-about .coverage-platforms {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
  margin-bottom: 28px;
}

.page-about .platform-card {
  padding: 16px 18px;
  border: 1px solid rgba(10, 25, 47, 0.1);
  border-left: 4px solid var(--c-indigo);
  background: rgba(75, 108, 183, 0.04);
}

.page-about .platform-label {
  display: block;
  margin-bottom: 6px;
  font-size: 16px;
  font-weight: 900;
  letter-spacing: 0.02em;
  color: var(--c-bg);
}

.page-about .platform-card p {
  margin: 0;
  font-size: 14px;
  line-height: 1.7;
  color: #334155;
}

.page-about .version-switch {
  padding: 24px;
  border: 1px solid rgba(10, 25, 47, 0.1);
  border-radius: 3px;
  background: linear-gradient(160deg, #eaf0f7 0%, #f4f8fb 100%);
}

.page-about .switch-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 20px;
}

.page-about .chart-tab {
  display: inline-block;
  padding: 8px 16px;
  border: 1px solid rgba(10, 25, 47, 0.2);
  border-radius: 2px;
  font-size: 14px;
  font-weight: 400;
  text-decoration: none;
  color: var(--c-bg);
  background: transparent;
  transition: background var(--transition-fast), border-color var(--transition-fast);
}

.page-about .chart-tab:first-child {
  background: var(--c-gold);
  border-color: var(--c-gold);
  color: var(--c-bg);
  font-weight: 700;
}

.page-about .version-switch:has(#panel-legacy:target) .chart-tab:first-child {
  background: transparent;
  border-color: rgba(10, 25, 47, 0.2);
  color: var(--c-bg);
  font-weight: 400;
}

.page-about .version-switch:has(#panel-legacy:target) .chart-tab:last-child {
  background: var(--c-gold);
  border-color: var(--c-gold);
  color: var(--c-bg);
  font-weight: 700;
}

.page-about .chart-tab:hover,
.page-about .chart-tab:focus-visible {
  background: var(--c-gold);
  border-color: var(--c-gold);
  color: var(--c-bg);
  font-weight: 700;
}

.page-about .version-board {
  padding: 20px;
  border-radius: 3px;
  border-left: 4px solid var(--c-gold);
  background: var(--c-paper);
}

.page-about .version-board h3 {
  margin: 0 0 12px;
  font-size: 18px;
  font-weight: 700;
  color: var(--c-bg);
}

.page-about .version-board ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .version-board li {
  position: relative;
  padding: 6px 0 6px 20px;
  font-size: 14px;
  line-height: 1.7;
  color: #334155;
}

.page-about .version-board li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 13px;
  width: 8px;
  height: 8px;
  background: var(--c-gold);
  border-radius: 50% 50% 50% 0;
  transform: rotate(45deg);
}

.page-about .version-panel-legacy {
  display: none;
}

.page-about #panel-legacy:target {
  display: block;
}

.page-about #panel-legacy:target ~ .version-panel-new {
  display: none;
}

.page-about .principles-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 18px;
}

.page-about .principle-card {
  position: relative;
  padding: 28px 24px;
  border-radius: 3px;
  border-top: 4px solid var(--c-red);
  background: linear-gradient(160deg, var(--c-bg) 0%, var(--c-bg-deep) 100%);
  color: var(--c-paper);
}

.page-about .principle-card:nth-child(2) {
  border-top-color: var(--c-gold);
}

.page-about .principle-card:nth-child(3) {
  border-top-color: var(--c-indigo);
}

.page-about .principle-num {
  display: inline-block;
  margin-bottom: 20px;
  padding: 4px 10px;
  border: 1px solid rgba(255, 215, 0, 0.4);
  border-radius: 2px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--c-gold);
}

.page-about .principle-card h3 {
  margin: 0 0 10px;
  font-size: 22px;
  font-weight: 700;
  color: var(--c-paper);
}

.page-about .principle-card p {
  margin: 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--c-gray);
}

.page-about .about-afterword {
  margin-top: 16px;
  padding: 28px 24px;
  border: 1px solid rgba(168, 178, 209, 0.24);
  border-radius: 3px;
  background:
    linear-gradient(135deg, rgba(255, 215, 0, 0.14) 0%, transparent 42%),
    linear-gradient(160deg, var(--c-bg) 0%, var(--c-bg-deep) 100%);
  color: var(--c-paper);
}

.page-about .afterword-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 24px;
}

.page-about .afterword-sheet h2 {
  margin: 8px 0 10px;
  font-size: 28px;
  font-weight: 900;
  color: var(--c-paper);
}

.page-about .afterword-sheet p {
  margin: 0;
  font-size: 15px;
  line-height: 1.7;
  color: var(--c-gray);
}

.page-about .afterword-links {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: 1fr;
  gap: 8px;
}

.page-about .afterword-links a {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 12px 16px;
  border: 1px solid var(--c-border);
  border-radius: 2px;
  background: rgba(11, 19, 43, 0.7);
  font-size: 15px;
  font-weight: 500;
  text-decoration: none;
  color: var(--c-paper);
  transition: background var(--transition-fast), border-color var(--transition-fast);
}

.page-about .afterword-links a:hover {
  background: rgba(255, 215, 0, 0.12);
  border-color: var(--c-gold);
}

.page-about .afterword-links .ar {
  font-size: 18px;
  color: var(--c-gold);
}

.page-about a:focus-visible {
  outline: 2px solid var(--c-gold);
  outline-offset: 2px;
  border-radius: 2px;
}

@media (min-width: 768px) {
  .page-about .about-hero-desc {
    font-size: 19px;
  }

  .page-about .story-layout {
    grid-template-columns: 1fr 0.8fr;
    align-items: start;
  }

  .page-about .data-stats {
    grid-template-columns: repeat(4, 1fr);
  }

  .page-about .data-layout {
    grid-template-columns: 1fr 0.78fr;
    align-items: start;
  }

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

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

  .page-about .afterword-grid {
    grid-template-columns: 1fr 1fr;
    align-items: center;
  }
}

@media (min-width: 1024px) {
  .page-about .about-layout {
    grid-template-columns: 300px minmax(0, 1fr);
    gap: 40px;
    align-items: start;
  }

  .page-about .about-sidebar {
    order: 1;
    position: sticky;
    top: calc(var(--header-height) + 16px);
  }

  .page-about .about-content {
    order: 2;
  }

  .page-about .section-block {
    padding: 40px 36px 44px;
  }
}