#display{
    height: 50px;
    font-size: 35px;
}
.row{
    display: flex;/*egymás mellé teszi a benne lévő elemeket*/
    width: 256px;
}
.col{
    border: 1px solid black;
    height: 50px;
    width: calc(calc(100% - calc(7px * 8)) / 4);
    margin: 7px;
    font-size: 35px;
    text-align: center;
    line-height: 50px;
    cursor: pointer;
}
.maxi-col{
    width: 100%;
}