|  | <!DOCTYPE html> | 
|  | <title>Reference for Scroll timeline with Web Animation using the root scroller</title> | 
|  | <style> | 
|  | html { | 
|  | min-height: 100%; | 
|  | min-width: 100%; | 
|  | padding-bottom: 100px; | 
|  | padding-right: 100px; | 
|  | } | 
|  |  | 
|  | #box { | 
|  | width: 100px; | 
|  | height: 100px; | 
|  | background-color: green; | 
|  | transform: translate(0, 100px); | 
|  | opacity: 0.5; | 
|  | will-change: transform; /* force compositing */ | 
|  | } | 
|  |  | 
|  | #covered { | 
|  | width: 100px; | 
|  | height: 100px; | 
|  | background-color: red; | 
|  | } | 
|  | </style> | 
|  |  | 
|  | <div id="box"></div> | 
|  | <div id="covered"></div> | 
|  |  | 
|  | <script> | 
|  | window.addEventListener('load', function() { | 
|  | // Move the scroller to halfway. | 
|  | const scroller = document.scrollingElement; | 
|  | const maxScroll = scroller.scrollHeight - scroller.clientHeight; | 
|  | scroller.scrollTop = 0.5 * maxScroll; | 
|  | }); | 
|  | </script> |