/* carte = empreinte stable */
.media-card{
  position: relative;
}

/* si tu mets w/h en HTML, aspect-ratio est bonus, pas obligatoire */
.media-card__img,
.media-card__video{
  width: 100%;
  height: auto;
  display: block;
}

#isab-masonry { position: relative; }

#isab-masonry .grid-sizer,
#isab-masonry .media-card {
  width: 100%;
}

@media (min-width: 700px){
  #isab-masonry .grid-sizer,
  #isab-masonry .media-card { width: calc(100%/2); }
}


@media (min-width: 1400px){
  #isab-masonry .grid-sizer,
  #isab-masonry .media-card { width: calc(100%/3); }
}

/* gutter : padding sur l’item + negative margin sur le container */
#isab-masonry { margin: -0.5em; }
#isab-masonry .media-card { padding: 0.5em; box-sizing: border-box; }