import { createTimeline, utils } from 'animejs';

const [ $reverseButton ] = utils.$('.reverse');

const tl = createTimeline()
.add('.circle',   { x: '15rem' })
.add('.triangle', { x: '15rem' }, 500)
.add('.square',   { x: '15rem' }, 1000);

const reverseTimeline = () => tl.reverse();

$reverseButton.addEventListener('click', reverseTimeline);

<div class="large row">
  <div class="medium pyramid">
    <div class="triangle"></div>
    <div class="square"></div>
    <div class="circle"></div>
  </div>
</div>
<div class="medium row">
  <fieldset class="controls">
    <button class="button reverse">Reverse</button>
  </fieldset>
</div>