.photo-grid {
  display: grid;
  gap: 1em;
  grid-template-columns: 1fr;
  width: 100%;
  max-width: 60em;
}
@container (width > 38em) {
  .photo-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}
@container (width > 60em) {
  .photo-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.photo-grid figure {
  border: 2px solid white;
  padding: .4em;
}
.photo-grid img {
  display: block;
  width: 100%;
}