:root {
  --bg: #f8fafc;
  --surface: #ffffff;
  --text: #1e293b;
  --muted: #64748b;
  --accent: #0f766e;
  --accent-light: #f0fdfa;
  --border: #e2e8f0;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Yu Gothic", "Meiryo", system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.8;
}
header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 1.25rem 1.5rem;
}
.nav-inner {
  max-width: 920px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}
.brand {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--accent);
  text-decoration: none;
  letter-spacing: 0.02em;
}
nav a {
  color: var(--muted);
  text-decoration: none;
  margin-left: 1.5rem;
  font-size: 0.95rem;
}
nav a:hover, nav a.active { color: var(--accent); font-weight: 600; }
main {
  max-width: 920px;
  margin: 2.2rem auto;
  padding: 0 1.5rem;
}
.hero {
  background: linear-gradient(135deg, #0f766e 0%, #115e59 100%);
  color: #ffffff;
  padding: 2.2rem 2rem;
  border-radius: 12px;
  margin-bottom: 2.2rem;
}
.hero h1 { font-size: 1.75rem; margin-bottom: 0.6rem; }
.hero p { opacity: 0.92; font-size: 0.98rem; }
.section-title {
  font-size: 1.25rem;
  margin-bottom: 1.1rem;
  padding-left: 0.75rem;
  border-left: 4px solid var(--accent);
}
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.25rem;
  margin-bottom: 2.5rem;
}
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1.4rem;
  transition: box-shadow 0.2s ease;
}
.card:hover { box-shadow: 0 6px 18px rgba(15, 23, 42, 0.06); }
.tag {
  display: inline-block;
  font-size: 0.75rem;
  background: var(--accent-light);
  color: var(--accent);
  padding: 0.15rem 0.55rem;
  border-radius: 999px;
  margin-bottom: 0.6rem;
  font-weight: 600;
}
.card h3 { font-size: 1.08rem; margin-bottom: 0.5rem; }
.card h3 a { color: var(--text); text-decoration: none; }
.card h3 a:hover { color: var(--accent); }
.card p { font-size: 0.9rem; color: var(--muted); }
.meta { font-size: 0.8rem; color: var(--muted); margin-top: 0.8rem; }
article {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 2rem;
}
article h1 { font-size: 1.6rem; margin-bottom: 0.5rem; }
article .meta { margin-bottom: 1.5rem; padding-bottom: 1rem; border-bottom: 1px solid var(--border); }
article h2 { font-size: 1.2rem; margin: 1.6rem 0 0.7rem; color: var(--accent); }
article p { margin-bottom: 1rem; }
article ul { margin: 0.5rem 0 1.2rem 1.4rem; }
pre {
  background: #0f172a;
  color: #e2e8f0;
  padding: 1rem;
  border-radius: 8px;
  overflow-x: auto;
  font-size: 0.85rem;
  margin: 1rem 0;
}
footer {
  max-width: 920px;
  margin: 3rem auto 2rem;
  padding: 1.5rem;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.85rem;
  text-align: center;
}