.flex_row {
        display: flex;
        flex-wrap: wrap;
        flex-direction:row;
    }

.flex_row_stretch {
    display: flex;
    flex-wrap: wrap;
    flex-direction: row;
    align-items:stretch;
}

.flex_row_center {
    display: flex;
    flex-wrap: wrap;
    flex-direction: row;
    align-items: center;
}

.flex_row_stiff div:nth-child(n){
    white-space:nowrap;
    flex:1;
}


    .flex_cell_450 {
        flex: 0 1 450px;
    }

    .flex_cell_400 {
        flex: 0 1 400px;
    }

    .flex_cell_350 {
        flex: 0 1 350px;
    }

    .flex_cell_300 {
        flex: 0 1 300px;
    }

    .flex_cell_250 {
        flex: 0 1 250px;
    }

    .flex_cell_150 {
        flex: 0 1 150px;
    }

    .flex_cell_100 {
        flex: 0 1 100px;
    }

    .flex_cell_50 {
        flex: 0 1 50px;
    }