:root {
  --accent: #3dcf7a;
  --text: #ffffff;
  --muted: #b7bec9;
  --side: 250px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background:
    linear-gradient(180deg, rgba(5, 10, 22, 0.72), rgba(5, 10, 22, 0.86)),
    #050a16 url("/img/bg.png?v=63") center / cover no-repeat fixed;
  display: grid;
  grid-template-columns: var(--side) 1fr;
}
a { color: var(--accent); }
.book-side {
  position: sticky;
  top: 0;
  height: 100vh;
  padding: 24px 18px;
  overflow: auto;
  background: rgba(5, 10, 22, 0.35);
}
.book-brand img { width: 150px; height: auto; display: block; margin: 0 auto 16px; }
.book-kicker {
  margin: 0 0 14px;
  text-align: center;
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 800;
}
.book-side nav { display: grid; gap: 4px; }
.book-side nav a {
  color: var(--text);
  text-decoration: none;
  padding: 8px 10px;
  font-size: 14px;
  font-weight: 600;
}
.book-side nav a:hover,
.book-side nav a.is-on {
  color: var(--accent);
  text-shadow: 0 0 10px rgba(61, 207, 122, 0.8);
}
.back {
  display: block;
  margin-top: 28px;
  text-align: center;
  color: var(--muted);
  text-decoration: none;
  font-size: 13px;
}
.book {
  max-width: 780px;
  padding: 48px 40px 80px;
}
.crumb {
  color: var(--muted);
  font-size: 12px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}
article { margin-bottom: 48px; scroll-margin-top: 24px; }
h1, h2, h3 { letter-spacing: 0.03em; }
h1 { font-size: 36px; margin: 8px 0 16px; }
h2 { font-size: 22px; color: var(--accent); }
p, li { color: #d5dae2; line-height: 1.6; }
kbd, code {
  background: rgba(61, 207, 122, 0.12);
  color: var(--accent);
  padding: 1px 6px;
  font-size: 0.95em;
}
@media (max-width: 860px) {
  body { grid-template-columns: 1fr; }
  .book-side { position: relative; height: auto; }
  .book { padding: 24px 18px 64px; }
}