/* Explicit chapter and part heads; narrative sections do not opt in. */
.part-head .head,
.thought.part > .strata > .head,
.chapter.chapter-part > .head {
  text-align: center;
}

.part-head .sentence-block,
.thought.part > .strata > .head {
  grid-column: 1 / -1;
}

.part-head,
.thought.part,
.chapter.chapter-part {
  border-top: 1px solid var(--rule-fine);
  padding-top: calc(var(--air) * 2);
  margin-top: calc(var(--air) * 2);
}

.part-head .head h2,
.thought.part .head h2,
.chapter.chapter-part > .head h2 {
  max-width: 900px;
  margin-inline: auto;
}

.part-head .head .subtitle,
.thought.part .head .subtitle,
.chapter.chapter-part > .head .subtitle {
  max-width: none;
  margin-inline: auto;
  font-family: var(--apparatus);
  font-size: 1.16rem;
  line-height: 1.55;
  color: var(--ink-quiet);
}