:root {
  --bg: #000000;
  --bg2: #1a1a1a;
  --bg3: #111111;
  --border: #2d2d2d;
  --text: #f5f5f7;
  --muted: #86868b;
  --accent: #2997ff;
  --accent2: #5ac8fa;
  --font: 'Noto Sans JP', -apple-system, BlinkMacSystemFont, 'Helvetica Neue', sans-serif;
}

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

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  font-size: 17px;
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--accent2); }

/* Header */
header {
  border-bottom: 1px solid var(--border);
  padding: 1.2rem 2rem;
  display: flex;
  align-items: center;
  gap: 1.2rem;
  backdrop-filter: saturate(180%) blur(20px);
  background: rgba(0,0,0,0.8);
  position: sticky;
  top: 0;
  z-index: 100;
}

header .site-title {
  font-size: 1.3rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--text);
}

header .site-tagline {
  font-size: 0.82rem;
  color: var(--muted);
  font-weight: 400;
}

/* Main */
main {
  max-width: 780px;
  margin: 0 auto;
  padding: 4rem 2rem;
}

/* Footer */
footer {
  border-top: 1px solid var(--border);
  padding: 2rem;
  text-align: center;
  font-size: 0.78rem;
  color: var(--muted);
}

/* Index — hero */
.hero {
  text-align: center;
  padding: 3rem 0 4rem;
}

.hero h1 {
  font-size: 2.8rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.2;
  background: linear-gradient(135deg, #f5f5f7 30%, #86868b);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 1rem;
}

.hero p {
  font-size: 1.05rem;
  color: var(--muted);
  font-weight: 400;
}

/* Article list */
.section-label {
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 1.5rem;
}

.article-list { list-style: none; }

.article-list li {
  border-bottom: 1px solid var(--border);
  padding: 1.8rem 0;
  transition: background 0.15s;
}

.article-list li:first-child { padding-top: 0; }

.article-list .article-title {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text);
  display: block;
  margin-bottom: 0.4rem;
  letter-spacing: -0.01em;
  transition: color 0.15s;
}

.article-list .article-title:hover { color: var(--accent); }

.article-list .article-meta {
  font-size: 0.78rem;
  color: var(--muted);
  margin-bottom: 0.4rem;
}

.article-list .article-desc {
  font-size: 0.9rem;
  color: #999;
  line-height: 1.6;
}

/* Tags */
.tag {
  display: inline-block;
  background: rgba(41,151,255,0.12);
  border: 1px solid rgba(41,151,255,0.25);
  border-radius: 20px;
  padding: 0.05em 0.65em;
  font-size: 0.72rem;
  color: var(--accent);
  letter-spacing: 0.02em;
}

/* Article page */
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.82rem;
  color: var(--accent);
  margin-bottom: 2.5rem;
}

.back-link:hover { color: var(--accent2); }

.article-header {
  margin-bottom: 3rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--border);
}

.article-header h1 {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.35;
  margin-bottom: 0.8rem;
  color: var(--text);
}

.article-header .meta {
  font-size: 0.8rem;
  color: var(--muted);
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

/* Article body */
.article-body h2 {
  font-size: 1.3rem;
  font-weight: 700;
  margin: 2.5rem 0 0.8rem;
  letter-spacing: -0.02em;
  color: var(--text);
}

.article-body h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin: 1.8rem 0 0.5rem;
  color: var(--accent2);
}

.article-body p {
  margin-bottom: 1.2rem;
  color: #d1d1d6;
}

.article-body strong { color: var(--text); }

.article-body ul, .article-body ol {
  margin: 0.5rem 0 1.2rem 1.4rem;
  color: #d1d1d6;
}

.article-body li { margin-bottom: 0.4rem; }

.article-body blockquote {
  border-left: 2px solid var(--accent);
  padding: 0.6rem 1.2rem;
  color: var(--muted);
  margin: 1.5rem 0;
  font-style: italic;
  background: var(--bg2);
  border-radius: 0 6px 6px 0;
}

.article-body code {
  background: var(--bg2);
  border: 1px solid var(--border);
  padding: 0.15em 0.45em;
  border-radius: 4px;
  font-size: 0.85em;
  font-family: 'SF Mono', 'Courier New', monospace;
  color: var(--accent2);
}

.article-body pre {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1.2rem 1.4rem;
  overflow-x: auto;
  margin: 1.5rem 0;
}

.article-body pre code {
  background: none;
  border: none;
  padding: 0;
  color: #e0e0e0;
}

@media (max-width: 600px) {
  header { padding: 1rem 1.2rem; }
  main { padding: 2.5rem 1.2rem; }
  .hero h1 { font-size: 2rem; }
  .article-header h1 { font-size: 1.5rem; }
}