* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
  }
  
  body {
    height: 100vh;
    display: flex;
    align-items: center;
  }

  .memory-game {
    width: 640px;
    height: 640px;
    margin: auto;
    display: flex;
    flex-wrap: wrap;
    perspective: 1000px;
    
  }
  .time{
    text-align: center;
    padding: 0 0 0 50px;
    font-weight: bold;
    font-size: 28px;
    color: rgb(231, 160, 6);
  }
  span{
    color: brown;
  }
  
  .memory-card {
    width: calc(25% - 10px);
    height: calc(30.333% - 10px);
    margin: 3px;
    position: relative;
    transform: scale(1);
    transform-style: preserve-3d;
    transition: transform .5s;
    box-shadow: 1px 1px 1px rgba(0,0,0,.3);
    border-radius: 15px;
    border: 2px solid rgb(27, 192, 77);
    
  }
  
  .memory-card:active {
    transform: scale(0.97);
    transition: transform .2s;
  }
  
  .memory-card.flip {
    transform: rotateY(180deg);
  }
  
  .front-face,
  .back-face {
    width: 100%;
    height: 100%;
    padding: 23px 13px;
    position: absolute;
    border-radius: 5px;
    border: none;
    backface-visibility: hidden;
  }
  
  .front-face {
    transform: rotateY(180deg);
  }
  @media(max-width:550px) {
      .memory-game{
        width: 440px;
        height: 440px;
      }
  }