:root {
  --background-top: #47585c;
  --background-bottom: #d4dcda;
}

html,
body {
  margin: 0;
  padding: 0;
  border: 0;
  font: inherit;
  overflow: hidden;
  vertical-align: baseline;
  background-image: linear-gradient(
    var(--background-bottom),
    var(--background-top)
  );
}

body {
  height: 100vh;
  line-height: 1;
  background-image: linear-gradient(
    var(--background-top),
    var(--background-bottom)
  );
}

iframe {
  width: 100%;
  height: 100%;
  border: none;
  position: fixed;
  top: 0;
  left: 0;
}