/* container */
.responsive-two-columns {
    display: flex;
    flex-wrap: wrap;
}

    /* columns */
    .responsive-two-columns > * {
        width: 100%;
        padding: 1rem;
    }

/* tablet breakpoint */
@media (min-width:768px) {
    .responsive-two-columns > * {
        width: 50%;
    }
}