// for this to work, also add body { margin: 0 and padding: 0 }
sS style_fullScreenBackgroundImage(S imgURL) {
  ret replaceDollarVars(newLinesToSpaces_trim([[
    background-image: url('$imgURL');
    background-repeat: no-repeat;
    background-size: contain;
    background-position: center;
    height: 100vh;
    width: 100vw;
    z-index: 0;
  ]]), +imgURL);
}