TryGhost/Ghost

.cover { background-size: cover!important; }
.contain { background-size: contain!important; }

@media (--breakpoint-not-small) {
  .cover-ns { background-size: cover!important; }
  .contain-ns { background-size: contain!important; }
}

@media (--breakpoint-medium) {
  .cover-m { background-size: cover!important; }
  .contain-m { background-size: contain!important; }
}

@media (--breakpoint-large) {
  .cover-l { background-size: cover!important; }
  .contain-l { background-size: contain!important; }
}