JSFiddle - React, Tailwind, and code Playground

HTML

<div class="sky"></div>
<div class="red"></div>

CSS

.sky {
	height:10000px; 
	width:100%; 
	position:absolute; 
	top:0px; 
	left:0px; 
	background-image:url(http://library.thinkquest.org/06aug/02339/clouds45.jpg); 
	z-index:1;
}

.red {
	height:10000px; 
	width:50%; 
	position:absolute; 
	top:0px; 
	right:25%; 
	background-image:url(http://www.charting-sustainability.org/writings/culture/red/red-pirate.jpg); 
	z-index:2; 
	background-position:center;
}

JavaScript

$(window).scroll(function() {
	  var scrollTop = $(window).scrollTop();
	  var divam = 1.2;
	  $(".sky").css({
		  "top":scrollTop/divam+"px",
		  "height":10000-(Math.round(scrollTop/divam))+"px"
	  });
	});