.gallery {
  background: #EEE;
}

.gallery-cell {
  width: 66%;
  height: 200px;
  margin-right: 10px;
  background: #8C8;
  counter-increment: gallery-cell;
}

/* cell number */
.gallery-cell:before {
  display: block;
  text-align: center;
  content: counter(gallery-cell);
  line-height: 200px;
  font-size: 80px;
  color: white;
}

.gallery-cell {
  width: 100%;
}

@media screen and ( min-width: 768px ) {
  /* half-width cells for larger devices */
  .gallery-cell { width: 50%; }
}