<div class="spacer">
</div>

<section class="l-accordion">
  <div class="l-accordion__slide" data-accordion-slide="1">
    <div class="l-accordion__inside">
      <h1>Slide 1</h1>
    </div>
  </div>
  <div class="l-accordion__slide" data-accordion-slide="2">
    <div class="l-accordion__inside">
      <h1>Slide 2</h1>
    </div>
  </div>
  <div class="l-accordion__slide" data-accordion-slide="3">
    <div class="l-accordion__inside">
      <h1>Slide 3</h1>
    </div>
  </div>
  <div class="l-accordion__slide" data-accordion-slide="4">
    <div class="l-accordion__inside">
      <h1>Slide 4</h1>
    </div>
  </div>


<div class="spacer">
</div>

body {
  margin: 0;
  font: 400 16px/1.5em 'Source Sans Pro', 'Segoe UI', 'Helvetica Neue', Roboto, Arial, sans-serif;

  max-width: 100vw;
}
.l-accordion {
  width: 100vw;
  height: 100vh;
  display: flex;
  flex-direction: row;
  justify-content: stretch;
}
.l-accordion__slide {
  flex: 1;
  transition: 0.4s ease-in-out;
  overflow: hidden;
  display: flex;
  border-left: 4px solid #fff;
}
[data-accordion-slide].l-accordion__slide:hover,
[data-accordion-slide].l-accordion__slide:focus {
  flex: 50;
}
.l-accordion__slide:first-child {
  border-left: 0;
  flex: 1.25;
  margin-left: -3em;
}
.l-accordion__slide:last-child {
  flex: 1.25;
  margin-right: -3em;
}
.l-accordion__inside {
  padding: 4em;
  background-cover: cover;
  background-position: center;
  margin: 0 -3em;
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
}
[data-accordion-slide="1"] .l-accordion__inside {
  background-image: url("https://i1.wp.com/www.soundpure.com/a/wp-content/uploads/2011/06/SR40V-horizontal.png?ssl=1");
  background-position: -50% 50%;
  background-repeat: no-repeat;
}
[data-accordion-slide="1"] .l-accordion__inside:hover {
  background-position: 50% 50%;
}


[data-accordion-slide="2"] .l-accordion__inside {
  background-image: url("https://i1.wp.com/www.soundpure.com/a/wp-content/uploads/2011/06/SR40V-horizontal.png?ssl=1");
  background-position: 60% 50%;
  background-repeat: no-repeat;
}
[data-accordion-slide="3"] .l-accordion__inside {
  background-image: url("https://i1.wp.com/www.soundpure.com/a/wp-content/uploads/2011/06/SR40V-horizontal.png?ssl=1");
  background-position: 72% 50%;
  background-repeat: no-repeat;
}
[data-accordion-slide="4"] .l-accordion__inside {
  background-image: url("https://i1.wp.com/www.soundpure.com/a/wp-content/uploads/2011/06/SR40V-horizontal.png?ssl=1");
  background-position: 100% 50%;
  background-repeat: no-repeat;
}
h1 {
  margin: 0;
  color: #fff;
  font-weight: 100;
  font-size: 3.5rem;
  white-space: nowrap;
  text-align: center;
  line-height: 1;
  text-shadow: 0 0 10px rgba(0,0,0,0.5);
}


.spacer {
  height: 50vh;
}