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HTML 

              
                <div id="nav">
  <button id="play">play</button>
  <button id="pause">pause</button>
  <button id="reverse">reverse</button>
</div>
<div id="cloudContainer"></div>
!

CSS 

              
                @import "compass";

#nav {
  background-color:black;
  padding:10px;
}

button {
  padding:10px;
  cursor:pointer;
}
#cloudContainer {
  position:relative;
  width:100%;
  height:600px;
background-color: rgba(15,131,194,1);/* Old Browsers */
@include background-image(linear-gradient(top, rgba(15,131,194,1) 0%, rgba(117,189,209,1) 44%, rgba(156,219,224,1) 100%));

  overflow:hidden;
}

.cloud{
 position:absolute;
width:100px;
  height:50px;
 border-radius:50%;
 background-color:white;
 
}
!

JS 

              
                var allClouds = new TimelineLite(),
    $cloudContainer = $("#cloudContainer");


function initClouds() {
  //loop through creation of 10 clouds
  for(var i = 0; i < 8; i ++){
    //dynamically create a cloud element
    var cloud = $('<div class="cloud"></div>').appendTo($cloudContainer);
    //set its initial position and opacity using GSAP
    TweenLite.set(cloud, {left:-100, top:i*40, opacity:0});
    //create a repeating timeline for this cloud
    var cloudTl = new TimelineMax({repeat:-1});
    //fade opacity to 1
    cloudTl.to(cloud, 0.5, {opacity:1})
    //move cloud across its container div with random duration. Start time = 0
    .to(cloud, 20 + (Math.random() * 25), {left:"100%", ease:Linear.easeNone}, 0)
    //0.5 seconds before timeline ends start fading opacity to 0 
    .to(cloud, 0.5, {opacity:0}, "-=0.5")
    //add this cloud's timeline to the allClouds timeline at a random start time.
    allClouds.add(cloudTl, Math.random()*35);
  }
}

//control allClouds timeline

$("#play").click(function(){
  allClouds.play();
});

$("#pause").click(function(){
  allClouds.pause();
});

$("#reverse").click(function(){
  allClouds.reverse();
});


initClouds();
!
999px

Console