Keep OptinMonster 2 columns on smaller screens.

gistfile1.txt

@media screen and (max-width: 768px) {
 html div#om-{{id}} .{{ns}}-row-content.Row__content div {
        flex-direction: row !important;
    }
html div#om-{{id}} .{{ns}}-column.{{ns}}-col-1.Column.om-column.optin-left-column-class {
    display: inline-block !important;
    width: 30% !important; /* adjust percentage */
}
html div#om-{{id}} .{{ns}}-column.{{ns}}-col-2.Column.om-column.optin-right-column-class {
    display: inline-block !important;
    width: 69.99% !important; /* adjust percentage */
}
}

Can be adjusted to add more columns, and edit the width percentage of each column