.die {
    position: relative;
    width: 48%;
    overflow: hidden;
    border: 1px solid black;
}

.die:before{
    content: "";
    display: block;
    padding-top: 100%;
}


.die-content {
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
}

.die-content div {
    display: table;
    width: 100%;
    height: 100%;
}


.die-content span {
    display: table-cell;
    text-align: center;
    vertical-align: middle;
    font-size: 10vw;
}