<!DOCTYPE html>
<html>
  <head>
    <title>My Awesome Screensaver</title>
    <style>
     * {
       padding: 0;
       margin: 0;
     }
    </style>
    <script>
     // load any incoming URL parameters. you could just use the
     // URLSearchParams object directly to manage these variables, but
     // having them in a hash is a little easier sometimes.
     var tmpParams = new URLSearchParams(document.location.search);
     window.urlParams = {};

     for(let k of tmpParams.keys() ) {
       window.urlParams[k] = tmpParams.get(k);
     }
    </script>
  </head>
  <body>
    <div id="wrapper">
      
    </div>
  </body>
  <script>
   var url = unescape(decodeURIComponent(window.urlParams.screenshot));
   document.querySelector("#wrapper").style.backgroundImage = 'url(' + url + ')';
  </script>

  <script language="javascript" type="text/javascript" src="./p5.min.js"></script>
  <script language="javascript" type="text/javascript" src="./sketch.js"></script>  
</html>

<!DOCTYPE html>
<html>
  <head>
    <title>My Awesome Screensaver</title>
    <style>
     body {
       background-color: black;
     }
     * {
       padding: 0;
       margin: 0;
     }
     #background {
       position: absolute;
       top: 0;
       left: 0;
       width: 100%;
       height: 100%;
       opacity: 0.45;
     }
     #wrapper {
       position: absolute;
       top: 0;
       left: 0;
     }
    </style>
    <script>
     // load any incoming URL parameters. you could just use the
     // URLSearchParams object directly to manage these variables, but
     // having them in a hash is a little easier sometimes.
     var tmpParams = new URLSearchParams(document.location.search);
     window.urlParams = {};

     for(let k of tmpParams.keys() ) {
       window.urlParams[k] = tmpParams.get(k);
     }
    </script>
  </head>
  <body>
    <div id="background"></div>
    <div id="wrapper"></div>
  </body>
  <script>
   var url = unescape(decodeURIComponent(window.urlParams.screenshot));
   document.querySelector("#background").style.backgroundImage = 'url(' + url + ')';

  </script>

  <script language="javascript" type="text/javascript" src="./p5.min.js"></script>
  <script language="javascript" type="text/javascript" src="./sketch.js"></script>  
</html>

Add some transparency to background
Add some transparency to background
