:root {
  --fg: #1a1a1a;
  --fg-sub: #555;
  --bg: #ffffff;
  --bg-sub: #f7f7f5;
  --border: #e5e5e0;
  --accent: #1a5f4a;
  --accent-hover: #14483a;
  --error: #b04040;
  --success: #1a5f4a;
  --max-w: 720px;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: 'Noto Sans JP', -apple-system, BlinkMacSystemFont, 'Hiragino Sans', 'Yu Gothic UI', sans-serif;
  color: var(--fg);
  background: var(--bg);
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}
.container {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 24px;
}
header {
  padding: 24px 0;
  border-bottom: 1px solid var(--border);
}
.logo {
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--fg);
  text-decoration: none;
}
.logo::after {
  content: '.dev';
  color: var(--accent);
  font-weight: 400;
}
main section {
  padding: 64px 0;
  border-bottom: 1px solid var(--border);
}
main section:last-child { border-bottom: none; }
h1 {
  font-size: 32px;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.4;
  margin-bottom: 24px;
}
h2 {
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 24px;
  letter-spacing: -0.01em;
}
h3 {
  font-size: 17px;
  font-weight: 700;
  margin-bottom: 8px;
}
p { margin-bottom: 16px; color: var(--fg-sub); }
p:last-child { margin-bottom: 0; }
a { color: var(--accent); }
footer {
  padding: 32px 0 48px;
  text-align: center;
  font-size: 13px;
  color: var(--fg-sub);
}
footer a {
  color: var(--fg-sub);
  text-decoration: none;
  margin: 0 8px;
}
footer a:hover { color: var(--accent); }
@media (max-width: 640px) {
  h1 { font-size: 26px; }
  main section { padding: 48px 0; }
}