.pwpswp-gallery--flex {
    width: 100%;
    display: flex;
    flex-wrap: wrap;
}

.pwpswp-gallery__item--flex {
    flex-grow: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-flow: column;
    margin: 2.5em 1.5em;
}

/*.pwpswp-gallery__link--flex {}
.pwpswp-gallery__image--flex {}
.pwpswp-gallery__caption--flex {}*/