/* (A) WHOLE PAGE */
* { box-sizing: border-box; }
body { background: #eee; }
 
/* (B) GALLERY WRAPPER */
.gallery {
  /* (B1) GRID LAYOUT - 3 IMAGES PER ROW */
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-gap: 20px;
 
  /* (B2) OPTIONAL WIDTH RESTRICT */
  max-width: 1000px;
  margin: 0 auto;
  overflow: hidden;
}

/* (C) GALLERY IMAGES */
.gallery img {
  /* (C1) DIMENSION */
  width: 100%;
  height: 150px; /* optional */
  padding: 10px;
  content-visibility: auto
 
  /* (C2) COLORS */
  border: 1px solid #ddd;
  background: #fff;
 
  /* (C3) IMAGE RESIZE */
  /* cover | contain | fill | scale-down */
  object-fit: contain;
  position: relative;
}

/* (D) ON SMALL SCREENS - 2 IMAGES PER ROW */
@media only screen and (max-width: 600px) {
  .gallery {
    grid-template-columns: repeat(2, 1fr);
  }
}