<section class="home-mast">
  <div class="home-mast__container">
    <div>
      <div class="absolute-bg" style="background-image: url('https://source.unsplash.com/3IEZsaXmzzs/1500x1200');"></div>
    </div>
    <div class="">
      <div class="absolute-bg" style="background-image: url('https://source.unsplash.com/BIZv8MWH00s/1500x1200');"></div>
    </div>
    <div class="">
      <div class="absolute-bg" style="background-image: url('https://source.unsplash.com/z55CR_d0ayg/1500x1200');"></div>
    </div>
    <div class="">
      <div class="absolute-bg" style="background-image: url('https://source.unsplash.com/-FgZlbzZ0R8/1500x1200');"></div>
    </div>
  </div>
</section>
// Variables
$color-alpha: #00a19b;
$color-beta: #bb1654;
$color-gamma: #006ba6;
$color-delta: #e6661f;

$color-white: #fff;

// Mixins
@mixin hover-overlay($background) {
  
  &:after {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    z-index: 0;

    height: 100%;
    width: 100%;

    background-color: $background;
    opacity: 0;
    transition: opacity 0.4s ease-in-out;
  }

  &:hover {

    &:after {
      opacity: 0.65;
      transition-delay: 0.6s;
    }
  }
}

// Base
* {
  box-sizing: border-box;
}

body {
  margin: 0;
}

// Helpers
.absolute-bg {
  position: absolute;
  top: 0;
  left: 0;
  z-index: 0;

  height: 100%;
  width: 100%;

  background-position: 50%;
  background-repeat: no-repeat;
  background-size: cover;
  overflow: hidden;
}

// Home Mast
.home-mast {
  height: 100vh;

  &__container {
    display: flex;
    height: 100%;

    & > * {
      position: relative;
      flex-grow: 1;
      padding: 1em;

      transition: flex-grow 0.6s cubic-bezier(0.4,0,0.2,1) 0.2s;

      &:hover {
        flex-grow: 3;
      }

      &:nth-child(1) {
        @include hover-overlay($color-alpha);
      }
      &:nth-child(2) {
        @include hover-overlay($color-beta);
      }
      &:nth-child(3) {
        @include hover-overlay($color-gamma);
      }
      &:nth-child(4) {
        @include hover-overlay($color-delta);
      }
    }
  }
}

External CSS

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External JavaScript

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