:root {
  --bg: #0d0d1a;
  --bg-card: rgba(255,255,255,0.03);
  --text: rgba(255,255,255,0.92);
  --text-muted: rgba(255,255,255,0.6);
  --accent: #6c63ff;
  --border: rgba(255,255,255,0.1);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Hiragino Sans", "Yu Gothic UI", "Meiryo", sans-serif;
  font-size: 15px;
  line-height: 1.8;
  letter-spacing: 0.02em;
}

main {
  max-width: 720px;
  margin: 0 auto;
  padding: 56px 24px 96px;
}

header {
  border-bottom: 1px solid var(--border);
  padding-bottom: 24px;
  margin-bottom: 40px;
}

h1 {
  font-size: 28px;
  margin: 0 0 8px;
  letter-spacing: 0.04em;
}

h2 {
  font-size: 18px;
  margin: 40px 0 12px;
  padding-left: 12px;
  border-left: 3px solid var(--accent);
  letter-spacing: 0.04em;
}

h3 {
  font-size: 15px;
  margin: 24px 0 8px;
  color: var(--accent);
}

p, li {
  color: var(--text);
}

ul, ol {
  padding-left: 20px;
}

li {
  margin-bottom: 6px;
}

.meta {
  color: var(--text-muted);
  font-size: 13px;
}

a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.2s;
}

a:hover, a:focus {
  border-bottom-color: var(--accent);
}

nav.toc {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px 24px;
  margin: 32px 0;
}

nav.toc h2 {
  margin-top: 0;
  font-size: 14px;
  color: var(--text-muted);
  border: none;
  padding: 0;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

nav.toc ul {
  margin: 8px 0 0;
  padding-left: 18px;
}

footer {
  margin-top: 80px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 13px;
  text-align: center;
}

footer a { margin: 0 8px; }

.callout {
  background: rgba(108,99,255,0.08);
  border-left: 3px solid var(--accent);
  padding: 12px 16px;
  border-radius: 4px;
  margin: 16px 0;
  font-size: 14px;
}