<div class="marquee">
  <div class="marquee__inner">
    <div class="marquee__content">MARQUEEEEEE!!!!!!</div>
  </div>
</div>
.marquee {
  position: relative;
  margin: 10px;
  padding: 10px;
  background-color: #eee;
  overflow: hidden;
  
  &__inner {
    display: inline-block;
    animation: marquee__inner 4s linear infinite alternate;
  }
  
  &__content {
    animation: marquee__content 4s linear infinite alternate;
    white-space: nowrap;
  }
}

@keyframes marquee__inner {
  0% { margin-left:0; }
  100% { margin-left: 100%; }
}
@keyframes marquee__content {
  0% { margin-left:0; }
  100% { margin-left:-100%; }
}

External CSS

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External JavaScript

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