:root {
  --bg: #f7f8fb;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #667085;
  --line: #e5e7eb;
  --accent: #2563eb;
  --accent-soft: #eff6ff;
  --max: 920px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP",
               "Hiragino Kaku Gothic ProN", "Yu Gothic", Meiryo, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.8;
}
a { color: var(--accent); }
header {
  background: #fff;
  border-bottom: 1px solid var(--line);
}
.nav {
  max-width: var(--max);
  margin: 0 auto;
  padding: 16px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}
.brand {
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
}
.navlinks {
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
  font-size: 14px;
}
.navlinks a {
  color: var(--muted);
  text-decoration: none;
}
.navlinks a:hover { color: var(--accent); }
main {
  max-width: var(--max);
  margin: 36px auto 64px;
  padding: 0 20px;
}
.hero, .card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 30px;
}
.hero {
  padding: 42px 34px;
  margin-bottom: 24px;
}
.badge {
  display: inline-block;
  font-size: 13px;
  font-weight: 600;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 4px 10px;
  border-radius: 999px;
  margin-bottom: 12px;
}
h1, h2, h3 {
  line-height: 1.4;
  margin-top: 0;
}
h1 { font-size: clamp(28px, 5vw, 42px); margin-bottom: 18px; }
h2 { font-size: 24px; margin-top: 36px; margin-bottom: 14px; }
h3 { font-size: 18px; margin-top: 26px; margin-bottom: 10px; }
p { margin: 0 0 16px; }
.lead {
  font-size: 18px;
  color: #475467;
}
.muted, .updated {
  color: var(--muted);
  font-size: 14px;
}
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 16px;
  margin: 24px 0;
}
.feature {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 22px;
}
.feature h3 { margin-top: 0; }
ul, ol { padding-left: 1.5em; }
li { margin-bottom: 8px; }
.notice {
  border-left: 4px solid var(--accent);
  background: var(--accent-soft);
  padding: 16px 18px;
  border-radius: 8px;
  margin: 20px 0;
}
footer {
  border-top: 1px solid var(--line);
  background: #fff;
}
.footer-inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 24px 20px;
  color: var(--muted);
  font-size: 13px;
}
.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  margin-bottom: 8px;
}
.footer-links a {
  color: var(--muted);
  text-decoration: none;
}
code {
  background: #f2f4f7;
  padding: 2px 6px;
  border-radius: 5px;
}
@media (max-width: 640px) {
  .nav { align-items: flex-start; flex-direction: column; }
  .hero, .card { padding: 24px 20px; }
}