#builder {
    container-name: demo;
    container-type: inline-size;
}

/* @container relies on JS shim */
@container demo (max-width: 980px) {
    .bld-2, .bld-2:last-of-type, .bld-3, .bld-3:last-of-type, .bld-4, .bld-4:last-of-type, .bld-6, .bld-6:last-of-type, .bld-8, .bld-8:last-of-type {
        float: none;
        width: 100%;
        margin-right: 0;
    }
}

/* Media Queries */
@media screen and (max-width: 980px) {
    .bld-2, .bld-2:last-of-type, .bld-3, .bld-3:last-of-type, .bld-4, .bld-4:last-of-type, .bld-6, .bld-6:last-of-type, .bld-8, .bld-8:last-of-type {
        float: none;
        width: 100%;
        margin-right: 0;
    }
}