.container {
display: grid;
}
.container.three-columns {
grid-template-columns: repeat(3, 1fr);
}
.container.four-columns {
grid-template-columns: repeat(4, 1fr);
}
.container div {
width: 3em;
height: 3em;
text-align: center;
line-height: 3em;
border-radius: 0.5em;
border: 0.2em solid lightgray;
}