.photo-gallery {
  position: relative;
}
.photo-gallery__list:after {
  content: "";
  display: block;
  clear: both;
}
.photo-gallery__sizer, .photo-gallery__item {
  width: calc(25% - 15px);
}
@media screen and (max-width: 820px) {
  .photo-gallery__sizer, .photo-gallery__item {
    width: calc(50% - 10px);
  }
}
.photo-gallery__item {
  float: left;
  margin-bottom: 20px;
}
.photo-gallery__item img {
  max-width: none;
  width: 100%;
}