style.css

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

#flip-card-game {
    margin: auto;
    width:700px;
    height: 700px;
}

#flip-card-game .container {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    padding: 10px;
    width: 100%;
    height: fit-content;
    background-color: rgb(121, 121, 255);
}

#flip-card-game .container>div {
    position: relative;
    margin: 5px;
    border-radius: 20px;
    width: 150px;
    height: 200px;
    transition: transform 1s;
    transform-style: preserve-3d;
}

#flip-card-game .container>div:hover {
    cursor: pointer;
}

#flip-card-game .container>div .front-face {
    position: absolute;
    top: 0;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    -moz-backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    transform: rotateY(180deg);
}

#flip-card-game .container>div .backFace {
    position: absolute;
    top: 0;
    width: 100%;
    height: 100%;
}

#flip-card-game .container>div img {
    border-radius: 20px;
    width: 100%;
    height: 200px;
}