:root {
  color-scheme: light dark;
  --bg: #f7f9fc;
  --surface: #ffffff;
  --text: #18212f;
  --muted: #5e6b7a;
  --line: #dbe3ec;
  --accent: #1769aa;
  --accent-strong: #0b4f84;
  --soft: #eaf4fc;
  --warning: #7a4d00;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #111820;
    --surface: #19232e;
    --text: #eef4fa;
    --muted: #b6c2ce;
    --line: #334252;
    --accent: #74b9ee;
    --accent-strong: #a8d7f7;
    --soft: #1d3447;
    --warning: #ffd38a;
  }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", sans-serif;
  font-size: 17px;
  line-height: 1.8;
}
a { color: var(--accent); text-underline-offset: 0.18em; }
a:hover { color: var(--accent-strong); }
header {
  border-bottom: 1px solid var(--line);
  background: var(--surface);
}
.nav {
  max-width: 920px;
  margin: 0 auto;
  padding: 14px 18px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}
.brand {
  color: var(--text);
  font-weight: 750;
  text-decoration: none;
  letter-spacing: 0.01em;
}
nav ul {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
}
nav a { text-decoration: none; font-weight: 650; }
main {
  max-width: 920px;
  margin: 0 auto;
  padding: 34px 18px 60px;
}
.hero {
  padding: 34px 28px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--surface);
  box-shadow: 0 10px 30px rgb(0 0 0 / 0.05);
}
h1, h2, h3 { line-height: 1.42; }
h1 { margin: 0 0 12px; font-size: clamp(2rem, 6vw, 3rem); }
h2 { margin-top: 2.3rem; font-size: 1.45rem; }
h3 { margin-top: 1.6rem; font-size: 1.15rem; }
p { margin: 0.75rem 0; }
ul { padding-left: 1.4rem; }
li { margin: 0.3rem 0; }
.lead { font-size: 1.08rem; color: var(--muted); }
.meta { color: var(--muted); }
.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 16px;
  margin-top: 24px;
}
.card {
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--surface);
}
.card h2 { margin-top: 0; font-size: 1.2rem; }
.button {
  display: inline-block;
  margin-top: 12px;
  padding: 11px 18px;
  border-radius: 999px;
  background: var(--accent);
  color: white;
  text-decoration: none;
  font-weight: 700;
}
.button:hover { color: white; background: var(--accent-strong); }
.notice {
  margin: 24px 0;
  padding: 16px 18px;
  border-left: 5px solid var(--accent);
  border-radius: 8px;
  background: var(--soft);
}
.policy {
  padding: 28px;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--surface);
}
footer {
  border-top: 1px solid var(--line);
  color: var(--muted);
  background: var(--surface);
}
.footer-inner {
  max-width: 920px;
  margin: 0 auto;
  padding: 22px 18px 34px;
}
.small { font-size: 0.92rem; }
@media (max-width: 640px) {
  .nav { align-items: flex-start; flex-direction: column; gap: 8px; }
  main { padding-top: 22px; }
  .hero, .policy { padding: 22px 18px; }
  body { font-size: 16px; }
}