html, body {
  padding: 2px;
  margin: 0px;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  grid-gap: 4px;
}

.item {
  overflow: hidden;
  position: relative;
  width: 100%;
  padding-bottom: 100%;
  height: 0;
}

img {
  position: relative;
  left: 50%;
  transform: translateX(-50%);
  display: block;
}