custom.scss

.project-card-image {
  width: 100%;
  height: calc(33.3% - 2*20px); /* Fluid 3 columns (inc. 20px gutter) */
}

.project-card-image-auto {
  width: 100%;
  height: auto;
}

@media screen and (max-width: 1199px) {
  .project-card-image {
    width: 100%;
    height: calc(50% - 20px); /* Fluid 2 columns (inc. 20px gutter) */
  }
}
@media screen and (max-width: 768px) {
  .project-card-image {
    width: 100%;
    height: 100%; /* 1 column */
  }
}