.fixed-size-square {
    display: table;
    width: 100px;
    height: 100px;
    background: #bdbdbd;
    float: right;
     border-style: solid;
    border-color: black;
    border-width: 4px;

}
.fixed-size-square span {
    display: table-cell;
    text-align: center;
    vertical-align: middle;
    color: white
}