.img-hover-popup {
  position: fixed;
  z-index: 1080;
  /* checkerboard transparency */
  background-image: linear-gradient(45deg, #ccc 25%, transparent 25%), linear-gradient(-45deg, #ccc 25%, transparent 25%), linear-gradient(45deg, transparent 75%, #ccc 75%), linear-gradient(-45deg, transparent 75%, #ccc 75%);
  background-size: 12px 12px;
  background-position: 0 0, 0 6px, 6px -6px, -6px 0;
  border-radius: 6px;
  box-shadow: 0 10px 40px rgba(0,0,0,.45);
  pointer-events: none;
  opacity: 0;
  transition: opacity .12s ease;
}

.img-hover-popup img {
  display: block;
  max-width: 90vw;
  object-fit: contain;
  background: transparent;
  border-radius: 6px;
}