layout.css

.layout--two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
}

.simple-box {
  padding: 0.5rem;
  background: #ccc;
}

.simple-box-title,
.simple-box-description {
  background: #fff;
}

File

core/modules/ckeditor5/tests/modules/ckeditor5_test/css/layout.css

.layout--two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
}

.simple-box {
  padding: 0.5rem;
  background: #ccc;
}

.simple-box-title,
.simple-box-description {
  background: #fff;
}