.trix-content .attachment-gallery > rich-text-attachment,
.trix-content .attachment-gallery > .attachment {
    flex: 1 0 33%;
    padding: 0 0.5em;
    max-width: 33%;
}
.trix-content .attachment-gallery.attachment-gallery--2 > rich-text-attachment,
.trix-content .attachment-gallery.attachment-gallery--2 > .attachment,
.trix-content .attachment-gallery.attachment-gallery--4 > rich-text-attachment,
.trix-content .attachment-gallery.attachment-gallery--4 > .attachment {
    flex-basis: 50%;
    max-width: 50%;
}
.trix-content rich-text-attachment .attachment {
    padding: 0 !important;
    max-width: 100% !important;
}