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                <div class="box gsap">GSAP</div>
<div class="box css">CSS Animation</div>


                /* The CSS animation being used */
@keyframes move-it {
  to { transform: translateX(100vw) translateX(-100%) rotate(360deg); }

.box {
  width: 200px;
  height: 200px;
  background: green;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #FFF;

.css { background: orange; }

html { overflow: hidden; }




var tl = new TimelineMax();

var duration = 2;
var ease = 'Power2.easeInOut';

/* Setting up the CSS animation on the element */
tl.set('.css', {
  animationName: 'move-it', // Animation name
  animationPlayState: 'paused', // Pause the animation so it doesn't play 
  animationTimingFunction: 'linear', // Linear easing so the animation follows GSAP's easing 
  animationDuration: duration + 's', // Length of the tween
  animationDelay: '0s', // Ensure there's no delay
  // Infinite iteration and alternating direction to prevent visual glitches when reaching 100% progress
  animationIterationCount: 'infinite', 
  animationDirection: 'alternate'

/* Now we tween the animation-delay to -duration */'.css', duration, {
  animationDelay: -duration + 's',
  ease: ease,
  onUpdate: function(){
    TweenLite.set(, { animationName: '' });
    TweenLite.set(, { animationName: 'move-it' });

/* Equivalent animation in GSAP, to show the animation is in sync */'.gsap', duration, {
  x: window.innerWidth,
  xPercent: -100,
  rotation: 360,
  ease: ease
}, 0);