style.css

* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
  }

  body {
    height: 100vh;
    display: flex;
    background: #3c6e71;
  }
  
  .wrapper {
    width: 640px;
    height: 640px;
    margin: auto;
    display: flex;
    flex-wrap: wrap;
    perspective: 1000px;
  }

  .card {
    width: calc(25% - 10px);
    height: calc(25% - 10px);
    margin: 5px;
    position: relative;
    box-shadow: 1px 1px 1px rgba(0,0,0,.3);
    transform: scale(1);
    transform-style: preserve-3d;
    transition: transform .5s;
  }

  .card:active{
    transform: scale(0.96);
    transition: transform .2s;
  }
  
  .front-card,
  .back-card {
    width: 100%;
    height: 100%;
    padding: 20px;
    position: absolute;
    border-radius: 5px;
    backface-visibility: hidden;
  }

  .front-card{
    transform: rotateY(180deg);
    background: #ffffff;
  }
  .back-card{
    background: #e9edc9;
  }

  .card.flip{
    transform: rotateY(180deg);
  }