html {
  height: 100%;
}

body {
  height: 100%;
  margin: 0;
  display: flex;
  justify-content: center;
  align-items: center;

  background: black;
}

.slide {
  max-width: 100%;
  max-height: 100%;
  display: none;
}

.slide-visible {
  display: block;
}