.cluster {
    display: grid;
    justify-items: center;
    align-items: center;
    font-size: 11px;
    font-weight: bold;
}
.cluster.m1 {
    background-image: url("icons/m1.png");
    height: 53px;
    width: 53px;
}
.cluster.m2 {
    background-image: url("icons/m2.png");
    height: 56px;
    width: 56px;
}
.cluster.m3 {
    background-image: url("icons/m3.png");
    height: 66px;
    width: 66px;
}
.cluster.m4 {
    background-image: url("icons/m4.png");
    height: 78px;
    width: 78px;
}