:root{
  --picture-width: 20em;
  --page-width: 90vw;
}

.title,
.subtitle,
.topmatter {
  display: block;
  margin-left: auto;
  margin-right: auto;
  text-align: center;
}

.topmatter {
  max-width: var(--page-width);
  text-align: left;
}

.collection-controls {
  margin-top: 2em;
}

.controls * {
  display: inline;
  margin-right: .25em;
}

.controls--pic_count,
.controls--topic,
.controls--summary {
  display: block;
  margin-bottom: 1em;
  margin-top: 0;
}

.picture-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(var(--picture-width), 1fr));
  /* grid-template-rows: repeat(auto-fit, var(--picture-width)); */
  row-gap: 1em;
  grid-column-gap: 1em;
  text-align: center;
  max-width: var(--page-width);
  margin-left: auto;
  margin-right: auto;
}

.picture img {
  max-width: var(--picture-width);
  max-height: var(--picture-width);
  width: auto;
  height: auto;
}

.hidden {
  display: none;
}