:root {
  --color-bg: #ffffff;
  --color-bg-alt: #eef2f9;
  --color-text: #1a1f3a;
  --color-text-muted: #4b557a;
  --color-accent: #2a3470;
  --color-accent-strong: #171d4b;
  --color-border: #d6dce8;
  --max-width: 760px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Hiragino Kaku Gothic ProN",
    "Hiragino Sans", "Yu Gothic UI", "Yu Gothic", Meiryo, sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  padding: 0;
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.75;
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.25rem;
}

a {
  color: var(--color-accent);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.site-header {
  border-bottom: 1px solid var(--color-border);
  background-color: var(--color-bg);
  position: sticky;
  top: 0;
  z-index: 10;
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 0.5rem 1rem;
  padding-top: 0.875rem;
  padding-bottom: 0.875rem;
}

.site-title {
  display: inline-flex;
  align-items: center;
  font-weight: 700;
  font-size: 1.125rem;
  color: var(--color-text);
  letter-spacing: 0.02em;
}

.site-logo {
  height: 40px;
  width: auto;
  display: block;
}

.hero-logo {
  display: block;
  max-width: 200px;
  width: 55%;
  height: auto;
  margin: 0 auto 0.75rem;
}

.site-nav {
  display: flex;
  gap: 1.25rem;
  flex-wrap: wrap;
  font-size: 0.9375rem;
}

.site-nav a {
  color: var(--color-text-muted);
}

.site-nav a:hover {
  color: var(--color-accent);
  text-decoration: none;
}

.hero {
  padding: 1.5rem 0 1.25rem;
  background: linear-gradient(135deg, #171d4b 0%, #2a3470 100%);
  color: #ffffff;
  text-align: center;
}

.hero h1 {
  font-size: 1.375rem;
  line-height: 1.4;
  margin: 0 0 0.25rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  color: #ffffff;
}

.hero .english-title {
  color: rgba(255, 255, 255, 0.78);
  margin: 0;
  font-size: 0.875rem;
}

.intro {
  padding: 2rem 0;
  border-bottom: 1px solid var(--color-border);
}

.intro p {
  margin: 0 auto;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 1rem;
  max-width: 40em;
}

.english-title {
  font-style: italic;
  color: var(--color-text-muted);
  margin: 0 0 1.75rem;
  font-size: 1rem;
}

.lead {
  font-size: 1.0625rem;
  color: var(--color-text-muted);
  margin: 0;
  max-width: 38em;
}

.section {
  padding: 3.5rem 0;
  border-bottom: 1px solid var(--color-border);
}

.section-alt {
  background-color: var(--color-bg-alt);
}

.section h2 {
  font-size: 1.5rem;
  font-weight: 600;
  margin: 0 0 1.5rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--color-accent-strong);
  display: inline-block;
  color: var(--color-accent-strong);
}

.section h3 {
  font-size: 1.125rem;
  font-weight: 600;
  margin: 2rem 0 0.75rem;
  color: var(--color-accent);
}

.section p {
  margin: 0 0 1rem;
}

.section ul {
  padding-left: 1.5rem;
  margin: 0 0 1rem;
}

.section ul li {
  margin-bottom: 0.375rem;
}

.info-list {
  margin: 1.25rem 0;
  display: grid;
  grid-template-columns: minmax(7rem, max-content) 1fr;
  gap: 0.75rem 1.5rem;
}

.info-list dt {
  font-weight: 600;
  color: var(--color-text-muted);
  font-size: 0.9375rem;
}

.info-list dd {
  margin: 0;
}

.info-list dd ul {
  padding-left: 1.25rem;
  margin: 0;
}

.note {
  font-size: 0.9375rem;
  color: var(--color-text-muted);
  border-left: 3px solid var(--color-border);
  padding: 0.25rem 0 0.25rem 1rem;
  margin: 1.5rem 0 0;
}

.ref-list {
  padding-left: 1.5rem;
  margin: 0;
}

.ref-list li {
  margin-bottom: 1.25rem;
  line-height: 1.7;
}

.ref-list em {
  font-style: italic;
}

sup a {
  text-decoration: none;
}

.site-footer {
  padding: 2rem 0;
  text-align: center;
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

.site-footer p {
  margin: 0;
}

.kana {
  display: inline-block;
  color: var(--color-text-muted);
  font-size: 0.8125rem;
  margin-top: 0.125rem;
}

@media (max-width: 600px) {
  .hero {
    padding: 2.5rem 0 2rem;
  }

  .hero h1 {
    font-size: 1.5rem;
  }

  .section {
    padding: 2.5rem 0;
  }

  .info-list {
    grid-template-columns: 1fr;
    gap: 0.25rem 0;
  }

  .info-list dt {
    margin-top: 0.5rem;
  }

  .site-nav {
    gap: 0.75rem 1rem;
    font-size: 0.875rem;
  }
}