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

body {
    height: 100vh;
    display: flex;
    background-color: #f0f1f2;
}

.main-area {
    width: 70%;
    height: 90%;
    margin: auto;
    display: flex;
    flex-wrap: wrap;
}

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

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

.card-front,
.card-back {
    width: 100%;
    height: 100%;
    padding: 20px;
    position: absolute;
    border-radius: 5px;
    backface-visibility: hidden;
    background-image: linear-gradient(to right bottom, #FBDB89, #F48982);
}

.card-front {
    transform: rotateX(180deg);
}

.card.flip {
    transform: rotateX(180deg);
}