body {
    background: #e4c143;
}

.board {
    width: 540px;
    height: 440px;
    margin: auto;
    display: flex;
    flex-wrap: wrap;
    perspective: 1000px;
}

.time {
    width: 520px;
    margin: auto;
    display: flex;
    flex-wrap: wrap;
    perspective: 1000px;
}

.cards {
    width: calc(25% - 10px);
    height: calc(33.333% - 10px);
    margin: 5px;
    position: relative;
    transform: scale(1);
    transform-style: preserve-3d;
    transition: transform .5s;
    box-shadow: 1px 1px 1px rgba(0, 0, 0, .3);
}

.cards:active {
    transform: scale(0.97);
    transition: transform .2s;
}

.cards.flip {
    transform: rotateY(180deg);
}

.front-face,
.back-face {
    width: 100%;
    height: 100%;
    padding: 20px;
    position: absolute;
    border-radius: 5px;
    background: #019787;
    backface-visibility: hidden;
}

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