*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}
body{
    height: 100vh;
    background-color: #343a40;
}
img{
    height: 100px;
    width: 100px;
}
.memory-game{
    height: 640px;
    width: 640px;
    margin: auto;
    display: flex;
    flex-wrap: wrap;
    perspective: 1000px;
}
.memory-card{
    width: calc(25% - 10px);
    height: calc(33.333% - 10px);
    margin: 5px;
    position: relative;
    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: mediumpurple;
    backface-visibility: hidden;
}
.front-face{
    transform: rotateY(180deg);
}
.navbar-brand{
    font-family: 'Oswald', sans-serif;
    font-size: xxx-large;
    margin-right: auto;
    margin-left: auto;
}
#reset-btn{
    color: white;
    background: mediumpurple;
    width: 640px;
    margin-top: 1em;
    margin-left: 33.33%;
}