:root {
  --primary-600: #2250df;
  --primary-500: #2b70ef;
  --primary-50: #f0f5ff;
  --radius-lg: 0.75rem;
  --text-base: 1.125rem;

  --bg: #fafafa;
  --surface: #ffffff;
  --text-primary: #1a1a2e;
  --text-secondary: #555570;
  --text-muted: #8888a0;
  --border: #e4e4ec;
  --accent-ai: #7c3aed;
  --accent-dev: #059669;
  --accent-product: #d97706;
  --accent-security: #dc2626;
  --accent-oss: #2563eb;
  --accent-infra: #0891b2;
  --accent-frontend: #db2777;
  --accent-data: #4f46e5;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", sans-serif;
  background: var(--bg);
  color: var(--text-primary);
  font-size: var(--text-base);
  line-height: 1.8;
  padding: 2rem 1rem;
}

.container {
  max-width: 720px;
  margin: 0 auto;
}

header {
  text-align: center;
  margin-bottom: 2.5rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border);
}

header h1 {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

header .date {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-top: 0.25rem;
}

header .tagline {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-top: 0.5rem;
}

.section {
  margin-bottom: 2rem;
}

.section-title {
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.section-title::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--border);
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.25rem;
  margin-bottom: 0.75rem;
  transition: box-shadow 0.15s ease;
}

.card:hover {
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
}

.card-header {
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  margin-bottom: 0.5rem;
}

.card h3 {
  font-size: 1.05rem;
  font-weight: 600;
  line-height: 1.5;
}

.card h3 a {
  color: var(--text-primary);
  text-decoration: none;
}

.card h3 a:hover {
  color: var(--primary-500);
}

.card .summary {
  color: var(--text-secondary);
  font-size: 0.92rem;
  line-height: 1.7;
}

.card .meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-top: 0.6rem;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.key-points {
  margin-top: 0.6rem;
  padding-left: 0.25rem;
}

.key-points ul {
  list-style: none;
  padding: 0;
}

.key-points li {
  position: relative;
  padding-left: 1.1rem;
  font-size: 0.88rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.key-points li::before {
  content: "•";
  position: absolute;
  left: 0;
  color: var(--primary-500);
  font-weight: 700;
}

.why-it-matters {
  margin-top: 0.6rem;
  padding: 0.6rem 0.75rem;
  background: #fffbeb;
  border-radius: 0.5rem;
  font-size: 0.88rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.tag {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 600;
  padding: 0.15rem 0.5rem;
  border-radius: 9999px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  flex-shrink: 0;
}

.content-type {
  font-size: 0.8rem;
  color: var(--text-muted);
  flex-shrink: 0;
  white-space: nowrap;
}

.tag-ai { background: #f3e8ff; color: var(--accent-ai); }
.tag-dev { background: #ecfdf5; color: var(--accent-dev); }
.tag-product { background: #fffbeb; color: var(--accent-product); }
.tag-security { background: #fef2f2; color: var(--accent-security); }
.tag-oss { background: var(--primary-50); color: var(--accent-oss); }
.tag-infra { background: #ecfeff; color: var(--accent-infra); }
.tag-frontend { background: #fdf2f8; color: var(--accent-frontend); }
.tag-data { background: #eef2ff; color: var(--accent-data); }

.highlight {
  background: linear-gradient(135deg, var(--primary-50), #f5f0ff);
  border-color: transparent;
}

.card.featured {
  background: linear-gradient(135deg, var(--primary-50), #f5f0ff);
  border: none;
  border-left: 4px solid var(--primary-500);
}

.quick-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
}

.quick-link:last-child {
  border-bottom: none;
}

.quick-link a {
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text-primary);
  text-decoration: none;
}

.quick-link a:hover {
  color: var(--primary-500);
}

.quick-summary {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.quick-link .meta {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-left: auto;
}

footer {
  text-align: center;
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.8rem;
}

footer a {
  color: var(--primary-500);
  text-decoration: none;
}

.archive-link {
  display: inline-block;
  margin-top: 1rem;
  color: var(--primary-500);
  font-size: 0.9rem;
  text-decoration: none;
}

.archive-link:hover {
  text-decoration: underline;
}

.stats-bar {
  display: flex;
  justify-content: center;
  gap: 1.5rem;
  padding: 0.6rem 0;
  margin-bottom: 1rem;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.toc {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 2rem;
}

.toc a {
  display: inline-block;
  padding: 0.25rem 0.6rem;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  text-decoration: none;
  border: 1px solid var(--border);
  border-radius: 9999px;
  transition: all 0.15s ease;
}

.toc a:hover {
  color: var(--primary-500);
  border-color: var(--primary-500);
}

.numbers-bar {
  display: flex;
  justify-content: center;
  gap: 2rem;
  padding: 1.25rem 0;
  margin-bottom: 2rem;
  border-bottom: 1px solid var(--border);
}

.number-item {
  text-align: center;
}

.number-value {
  display: block;
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--primary-600);
  letter-spacing: -0.02em;
}

.number-label {
  display: block;
  font-size: 0.7rem;
  color: var(--text-muted);
  margin-top: 0.15rem;
  max-width: 120px;
}

.card.deep-dive {
  border-left-width: 6px;
}

.card.deep-dive .summary {
  font-size: 0.95rem;
}

.editorial {
  margin-top: 0.6rem;
  padding: 0.6rem 0.75rem;
  background: #f0f5ff;
  border-radius: 0.5rem;
  font-size: 0.88rem;
  color: var(--text-secondary);
  line-height: 1.6;
  border-left: 3px solid var(--primary-500);
}

.engagement {
  color: var(--accent-product);
  font-weight: 600;
}

.weekly-keywords {
  margin-bottom: 2rem;
}

.keyword-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin: 0.75rem 0;
}

.keyword-chip {
  display: inline-block;
  padding: 0.3rem 0.75rem;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--primary-600);
  background: var(--primary-50);
  border-radius: 9999px;
}

.keyword-summary {
  font-size: 0.88rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

@media (max-width: 600px) {
  body { padding: 1rem 0.75rem; }
  header h1 { font-size: 1.4rem; }
  .card { padding: 1rem; }
  .card-header { flex-wrap: wrap; gap: 0.4rem; }
  .card h3 { font-size: 0.95rem; width: 100%; }
  .card .meta { flex-wrap: wrap; gap: 0.4rem; }
  .card .summary { font-size: 0.85rem; }
  .quick-link { flex-wrap: wrap; }
  .quick-link .meta { margin-left: 0; width: 100%; margin-top: 0.25rem; }
  .stats-bar { gap: 0.75rem; font-size: 0.72rem; }
  .numbers-bar { flex-direction: column; align-items: center; gap: 1rem; }
  .number-label { max-width: 240px; }
  .number-value { font-size: 1.25rem; }
  .number-label { font-size: 0.7rem; }
  .toc { gap: 0.35rem; }
  .toc a { font-size: 0.7rem; padding: 0.2rem 0.5rem; }
  .editorial { font-size: 0.82rem; }
  .why-it-matters { font-size: 0.82rem; }
  .key-points li { font-size: 0.82rem; }
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f0f1a;
    --surface: #1a1a2e;
    --text-primary: #e4e4ec;
    --text-secondary: #a0a0b8;
    --text-muted: #6b6b80;
    --border: #2a2a3e;
    --primary-50: #1a1a3e;
    --primary-600: #5b8af5;
    --primary-500: #6b9af5;
  }

  .tag-ai { background: #2d1b69; }
  .tag-dev { background: #0a3d2a; }
  .tag-product { background: #3d2a0a; }
  .tag-security { background: #3d0a0a; }
  .tag-oss { background: #0a1a3d; }
  .tag-infra { background: #0a2d3d; }
  .tag-frontend { background: #3d0a2d; }
  .tag-data { background: #1a1a4d; }

  .card.featured,
  .highlight {
    background: linear-gradient(135deg, #1a1a3e, #1f1a3e);
  }

  .why-it-matters { background: #2a2510; }
  .editorial { background: #141a2e; }
  .keyword-chip { background: #1a1a3e; }
}

.site-nav {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.75rem;
}

.site-nav a {
  display: inline-block;
  padding: 0.25rem 0.6rem;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  text-decoration: none;
  border: 1px solid var(--border);
  border-radius: 9999px;
  transition: all 0.15s ease;
}

.site-nav a:hover,
.site-nav a.active {
  color: var(--primary-500);
  border-color: var(--primary-500);
}