:root {
  --gap: 1rem;
}

body {
  display: grid;
  grid-template-columns: [sidebar] 1fr [content] 3fr;
  grid-gap: var(--gap);
  overflow: hidden;
  padding: 0;
  margin: 0;

  max-width: unset;
  width: 100vw;
  height: 100vh;
}

.book.sidebar {
  padding: 0 var(--gap);
  overflow-y: auto;
  resize: horizontal;
}

.book.content {
  padding: var(--gap);
  overflow-y: auto;
}

article h1 {
  font-size: 2rem;
}