/* xs < 768 */
@media screen and (max-width: 767px) {
    body {
        font-size: 0.9em;
    }
}

/* sm */
@media screen and (min-width: 768px) {
    body {
        font-size: 1em;
    }
}

/* md */
@media screen and (min-width: 992px) {
    body {
        font-size: 1.2em;
    }
}

/* lg */
@media screen and (min-width: 1200px) {
    body {
        font-size: 1.3em;
    }
}