:root {
  --body-font: "Hiragino Mincho Pro", "Noto Serif JP", "Yu Mincho", Georgia, serif;
  --sans-font: "Hiragino Kaku Gothic Pro", "Noto Sans JP", "Yu Gothic", "Helvetica Neue", sans-serif;
  --max-width: 880px;
  --accent: #0055cc;
  --border: #d8d8d8;
}
html { font-size: 16px; }
body {
  font-family: var(--body-font);
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 2em 5em;
  line-height: 1.9;
  color: #1c1c1c;
  background: #fff;
}
h1, h2, h3, h4, h5, h6 {
  font-family: var(--sans-font);
  font-weight: bold;
  margin-top: 1.8em;
  line-height: 1.4;
}
h1 { font-size: 1.75em; border-bottom: 2px solid #333; padding-bottom: 0.3em; }
h2 { font-size: 1.35em; border-bottom: 1px solid var(--border); padding-bottom: 0.2em; }
h3 { font-size: 1.12em; }
p  { margin: 0.8em 0; }
a  { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
blockquote {
  border-left: 3px solid #aaa;
  margin: 1em 0;
  padding: 0.4em 1em;
  color: #555;
}
code {
  font-size: 0.9em;
  background: #f5f5f5;
  padding: 0.1em 0.35em;
  border-radius: 3px;
}
pre { background: #f5f5f5; padding: 1em; border-radius: 4px; overflow-x: auto; }
pre code { background: none; padding: 0; }
table { border-collapse: collapse; width: 100%; margin: 1em 0; }
th, td { border: 1px solid #ccc; padding: 0.45em 0.75em; text-align: left; }
th { background: #f0f0f0; font-family: var(--sans-font); }
hr { border: none; border-top: 1px solid var(--border); margin: 2em 0; }
/* Math display blocks */
.math.display { overflow-x: auto; padding: 0.5em 0; }
/* Navigation bar */
.site-nav {
  font-family: var(--sans-font);
  font-size: 0.88em;
  background: #f8f8f8;
  border-bottom: 1px solid var(--border);
  padding: 0.55em 2em;
  margin: 0 -2em 2.5em;
}
.site-nav a { color: var(--accent); }
/* Footer */
footer {
  margin-top: 3.5em;
  padding-top: 1em;
  border-top: 1px solid var(--border);
  font-size: 0.82em;
  color: #666;
  font-family: var(--sans-font);
}