@media only screen and (min-width: 768px){
    /* for desktops */
    .memory-game{
        height: 600px;
        width: 600px;
    }
}
@media only screen and (max-width: 768px){
    .memory-game{
        height: 60vh;
        width: 100vw;
    }
}
*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}
body{
    height: 100vh;
    display: flex;
    background: #333333;;
}
.memory-game{
    margin: auto;
    display: flex;
    flex-wrap: wrap;
    perspective: 1000px;
}
.memory-card{
    width: calc(25% - 10px);
    height: calc(33.33% - 10px);
    position: relative;
    margin: 5px;
    transform: scale(1);
    transform-style: preserve-3d;
    transition: transform .5s;
}
.memory-card:active{
    transform: scale(.97);
    transition: transform .2s;
}
.memory-card.flip{
    transform: rotateY(180deg);

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

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