/* (A) WHOLE PAGE */
* {
  font-family: Arial, Helvetica, sans-serif;
  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, minmax(0, 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: 180px; /* optional */
  padding: 10px;

  /* (C2) COLORS */
  border: 1px solid #ddd;
  background: #fff;

  /* (C3) IMAGE RESIZE */
  /* cover | contain | fill | scale-down */
  object-fit: cover;
}

/* (D) ON SMALL SCREENS - 2 IMAGES PER ROW */
@media only screen and (max-width: 600px) {
  .gallery {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

/* (E) OPTIONAL ZOOM ON HOVER */
.gallery img:hover {
  z-index: 9;
  transform: scale(1.3);
  /* linear | ease | ease-in | ease-out | ease-in-out */
  transition: transform ease 0.5s;
}

/* (F) FULLSCREEN MODE */
.gallery img.full {
  position: fixed;
  top: 0; left: 0; z-index: 999;
  width: 100vw; height: 100vh;
  object-fit: contain;
  background: rgba(0, 0, 0, 0.7);
}
.gallery img.full:hover {
  z-index: 999;
  transform: none;
}