<section class="skewed" id="wrapper">
  <div class="layer bottom">
    <div class="content-wrap">
      <div class="content-body">
        <h1>Happy Halloween</h1>
      </div>
      <img src="https://res.cloudinary.com/dbpolimgc/image/upload/v1539199490/Mask%20Assets/Mask-bw.jpg" alt="mask negative">
    </div>
  </div>
  
  <div class="layer top">
    <div class="content-wrap">
      <div class="content-body">
        <h1>Trick or Treat</h1>
      </div>
      <img src="https://res.cloudinary.com/dbpolimgc/image/upload/v1539199490/Mask%20Assets/Mask-actual.jpg" alt="mask">
    </div>
  </div>
  
  <div class="handle"></div>
</section>

body {
  margin: 0
  padding: 0
  font-size: 100%;
  line-height: 1.6;
  font-family: Helvetica, sans-serif;
}

#wrapper {
  position: relative;
  width: 100%;
  min-height: 55vw;
  overflow: hidden;
}

.layer {
  position: absolute;
  width: 100vw;
  min-height: 55vw;
  overflow: hidden;
}

.layer .content-wrap {
  position: absolute;
  width: 100vw;
  min-height: 55vw;
}

.layer .content-body {
  position: absolute;
  width: 25%;
  top: 50%;
  text-align: center;
  transform: translateY(-50%);
  color: #fff;
}

.layer img {
  position: absolute;
  width: 35%;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.layer h1 {
  font-size: 2em;
}

.bottom {
  background: #222;
  z-index: 1;
}

.bottom .content-body {
  right: 5%;
}

.bottom h1 {
  color: #fdab00;
}

/* top layer */
.top {
  background: #eee;
  color: #222;
  z-index: 2;
  width: 50vw;
}

.top .content-body {
  left: 5%;
  color: #222;
}

.handle {
  position: absolute;
  height: 100%;
  display: block;
  background-color: #fdab00;
  width: 5px; /*for the bar*/
  top: 0;
  left: 50%;
  z-index: 3;
}

/* skew effect */
.skewed .handle {
  top: 50%;
  transform: rotate(30deg) translateY(-50%);
  height: 200%;
  transform-origin: top;
}

.skewed .top {
  transform: skew(-30deg);
  margin-left: -1000px;
  width: calc(50vw + 1000px);
}

.skewed .top .content-wrap {
  transform: skew(30deg);
  margin-left: 1000px;
}

@media(max-width: 768px) {
  body {
    font-size: 75%;
  }
}

document.addEventListener('DOMContentLoaded', function() {
  let wrapper = document.getElementById('wrapper');
  let topLayer = wrapper.querySelector('.top');
  let handle = wrapper.querySelector('.handle');
  let skew = 0;
  let delta = 0;
  
    if(wrapper.className.indexOf('skewed') != -1) {
    skew = 1000;
  }

  wrapper.addEventListener('mousemove', function(event) {
    delta = (event.clientX - window.innerWidth / 2) * 0.5;
    handle.style.left = event.clientX + delta + 'px';
    topLayer.style.width = event.clientX + skew + delta + 'px';
  });
});