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

body {
  height: 100vh;
  display: flex;
  background-color: #FFEC09;
}

.memory-game {
  width: 800px;
  height: 640px;
  margin: auto;
  display: flex;
  flex-wrap: wrap;
  perspective: 1000px;
}

.memory-card {
  width: calc(25% - 10px);
  height: calc(33.33% - 10px);
  margin: 5px;
  position: relative;
  transform: scale(1);
  transform-style: preserve-3d;
  transform: transition .5s;
  box-shadow: 1px 1px 1px rgba(0,0,0,.3);
}

.memory-card:active {
  transform: scale(0.90);
  transition: transform .3s;
}

.memory-card.flip {
  transform: rotateY(180deg);
  transition: transform .3s;
}

.front-face, .back-face {
  width: 100%;
  height: 100%;
  padding: 20px;
  position: absolute;
  border-radius: 5px;
  background-color: orange;
  backface-visibility: hidden;
}

.front-face {
  transform: rotateY(180deg);
}

@media only screen and (max-device-width: 480px) {
  .memory-game {
      width: 400px;
      height: 320px;
      margin: auto;
      display: flex;
      flex-wrap: wrap;
      perspective: 1000px;
  }
}