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HTML 

              
                <!DOCTYPE html>
<meta charset="utf-8">
<style>



</style>
<body onclick="myFunction()">
  <div class="fullscreen-bg ">
  <video style="display: none;" loop muted autoplay class="fullscreen-bg__video">
        <source src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/93690/berlin.mp4" type="video/mp4">
    </video>
</div>
  <div id="thing" style="background: red; height: 100px; width: 100px; position: absolute; display: none;"></div>
  	<div id="rain"></div>

<script src="//d3js.org/d3.v3.min.js"></script>
<script>

var width = Math.max(960, innerWidth),
    height = Math.max(500, innerHeight);

var x1 = width / 2,
    y1 = height / 2,
    x0 = x1,
    y0 = y1,
    i = 0,
    r = 200,
    τ = 2 * Math.PI;

var canvas = d3.select("#rain").append("canvas")
    .attr("width", width)
    .attr("height", height)
    .on("ontouchstart" in document ? "touchmove" : "mousemove", move);

var context = canvas.node().getContext("2d");
context.globalCompositeOperation = "lighter";
context.lineWidth = 2;

d3.timer(function() {
  context.clearRect(0, 0, width, height);

  var z = d3.hsl(++i % 360, 1, .5).rgb(),
      c = "rgba(" + z.r + "," + z.g + "," + z.b + ",",
      x = x0 += (x1 - x0) * .1,
      y = y0 += (y1 - y0) * .1;

  d3.select({}).transition()
      .duration(1000)
      .ease(Math.sqrt)
      .tween("circle", function() {
        return function(t) {
          context.strokeStyle = c + (1 - t) + ")";
          context.beginPath();
          context.arc(x, y, r * t, 0, τ);
          context.stroke();
        };
      });
});

function move() {
  var mouse = d3.mouse(this);
  x1 = mouse[0];
  y1 = mouse[1];
  d3.event.preventDefault();
}

</script>
!

CSS 

              
                
#rain {
  position: relative;
  top: 0;
  left: 0;
  display: flex;
  width:100%;
    height: 100%;
  /*overflow:hidden;*/
  /*border: 1px solid #fff;*/
}

.fullscreen-bg {
  position: absolute;
  width: 110%;
  margin-left: -100px;
  height: 100%;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  overflow: hidden;
  z-index: -100;
}
@keyframes mynewmove {
  from {
    transform: scale(1) skew(0);
    border-color: rgba(62,190,155, 1);
  }

  to {
    transform: scale(2) skew(0);
  }
}

@keyframes mynewmove2 {
  from {
    transform: scale(1) skew(0);
    border-color: rgba(58,144,171, 1);
  }

  to {
    transform: scale(2) skew(0);
  }
}
!

JS 

              
                function myFunction() {
$('video').fadeIn(3000);
}

setInterval(() => {
          var parent=document.getElementById('rain');

          console.log('background',   document.body.style.backgroundColor);
          var div = document.createElement("div");
          div.style.position='absolute';
          div.classList.add('drop');
          div.style.width='55px';
          div.style.height='25px';
          div.style.border="10px solid rgba(62,190,155,0)";

          div.style.borderRadius='50%';

          var top = Math.random()*100+'%';
          div.style.top=top;

          var left = Math.random()*100+'%';

          div.style.left=left;


          div.style.animation = "mynewmove 3s 1"; 

          parent.appendChild(div);
       
       
       // rain 2
                var parent=document.getElementById('rain');

          console.log('background',   document.body.style.backgroundColor);
          var div = document.createElement("div");
          div.style.position='absolute';
          div.classList.add('drop');
          div.style.width='55px';
          div.style.height='25px';
          div.style.border="thin solid rgba(58,144,171,0)";

          div.style.borderRadius='50%';

          var top = Math.random()*100+'%';
          div.style.top=top;

          var left = Math.random()*100+'%';

          div.style.left=left;


          div.style.animation = "mynewmove2 2s 1"; 

          parent.appendChild(div);

        }, 100);
!
999px

Console