:root {
  --bg: #f7f8fb;
  --surface: #ffffff;
  --text: #1b1f2a;
  --muted: #5b6474;
  --line: #e2e6ee;
  --accent: #0a84c6;
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b0f1a;
    --surface: #121829;
    --text: #e6eaf2;
    --muted: #9aa4b8;
    --line: #232c42;
    --accent: #3fd0ff;
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Hiragino Sans", "Hiragino Kaku Gothic ProN",
    "Noto Sans JP", "Segoe UI", sans-serif;
  line-height: 1.8;
}
header.site {
  border-bottom: 1px solid var(--line);
  background: var(--surface);
}
header.site .inner, main, footer.site .inner {
  max-width: 760px;
  margin: 0 auto;
  padding: 0 16px;
}
header.site .inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 56px;
  gap: 12px;
}
.brand { font-weight: 700; letter-spacing: 0.04em; color: var(--text); text-decoration: none; }
nav.lang a { margin-left: 12px; font-size: 14px; }
main { padding-top: 32px; padding-bottom: 48px; }
h1 { font-size: 28px; line-height: 1.4; margin: 0 0 8px; }
h2 { font-size: 20px; margin: 40px 0 8px; padding-top: 8px; border-top: 1px solid var(--line); }
h3 { font-size: 16px; margin: 24px 0 4px; }
p, li { font-size: 16px; }
ul { padding-left: 1.4em; }
a { color: var(--accent); overflow-wrap: anywhere; }
.meta { color: var(--muted); font-size: 14px; }
.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 20px;
  margin: 16px 0;
}
.card h2 { border-top: 0; margin-top: 0; padding-top: 0; }
section.lang-block + section.lang-block { margin-top: 64px; padding-top: 24px; border-top: 3px double var(--line); }
footer.site { border-top: 1px solid var(--line); color: var(--muted); font-size: 13px; }
footer.site .inner { padding-top: 16px; padding-bottom: 32px; }