:root {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", sans-serif;
  color: #172033;
  background: #f6f8fb;
}
* { box-sizing: border-box; }
body { margin: 0; line-height: 1.75; }
header, main, footer { max-width: 880px; margin: 0 auto; padding: 24px; }
header { padding-top: 56px; }
.card {
  background: white;
  border: 1px solid #e4e8ef;
  border-radius: 16px;
  padding: 28px;
  box-shadow: 0 8px 30px rgba(27,39,63,.06);
}
h1 { font-size: 2rem; margin: 0 0 8px; }
h2 { margin-top: 2rem; font-size: 1.25rem; }
a { color: #2457d6; }
nav a { margin-right: 18px; }
.small { color: #5f6b7a; font-size: .92rem; }
footer { color: #667085; font-size: .9rem; padding-bottom: 48px; }
code { background: #eef2f7; padding: .15em .4em; border-radius: 5px; }
ul { padding-left: 1.4rem; }