* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html, body {
  width: 100%;
  height: 100%;
  overflow: hidden;
  background-color: #000;
}

img#mainImage {
  display: block;
  max-width: 100vw;
  max-height: 100vh;
  width: auto;
  height: auto;
  margin: auto;
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
}