CSS

css grid first child

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(45px, 1fr));
}
.grid div {
  border: 1px solid blue;
}

.grid div {
  grid-column: span 2;
}
.grid div:first-child, .grid div:last-child {
  grid-column: span 1;
}