.columns {
    max-width: 1200px;
    margin: 6rem auto 0;
    display: flex;
}
@media only screen and (min-width: 1200px) {
    .columns__single {
        display: inline-block;
        vertical-align: top;
    }

    .columns--article {
        display: flex;
    }

    .columns__single--article {
        display: flex;
        flex-direction: column;
        flex-grow: 1;
    }

    .columns__child--article:last-child {
        flex-grow: 1;
    }
}