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

body {
    font-family: 'Press Start 2P', sans-serif;
    height: 100vh;
    display: flex;
    background: #77abb7;
    margin: 0 auto;
}

h2 {
    display: flex;
    justify-content: center;
    padding: 20px 0;
}

.wrapper{
    margin: auto;
}

.memory-game {
    width: 640px;
    height: 640px;
    display: flex;
    flex-wrap: wrap;
}

.memory-card {
    width: calc(25% - 10px);
    height: calc(25% - 10px);
    margin: 5px;
    position: relative;
    box-shadow: 1px 1px 1px rgba(0,0,0,.3);
    perspective: 1000px;
}

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

.back-face, .front-face {
    width: 100%;
    height: 100%;
    position: absolute;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    transition: 1s;
}

.memory-card.flip .front-face{
    transform: rotateY(360deg);
}

.memory-card.flip .back-face{
    transform: rotateY(180deg);
}

.memory-card.hide {
    visibility: hidden;
}