html, body {
  padding: 0;
  margin:  0;
  height: 100%;
  width: 100%;
  overflow: hidden;
  background-color: white;
}

.img-container {
  background-image: linear-gradient(45deg, #ececec 25%, transparent 25%), linear-gradient(-45deg, #ececec 25%, transparent 25%), linear-gradient(45deg, transparent 75%, #ececec 75%), linear-gradient(-45deg, transparent 75%, #ececec 75%);
  background-size: 40px 40px;
  background-position: 0 0, 0 20px, 20px -20px, -20px 0px;

  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;

  height: 100%;
  overflow: auto;
}

.img-container > img,
.img-container > iframe {
  /* Oddly, this is necessary for vertical centering + auto */
  margin: 0 auto;
  position: relative;
  left: 0px;
  top:  0px;
  image-rendering: pixelated;
  flex: 0 0 auto;
}