style.css

@import url('https://fonts.googleapis.com/css2?family=Poppins&display=swap');
*{
    font-family: "Poppins", sans-serif;
}
body {
    height: 100%
    display: flex;
}

h3{
    font-weight: bold;
    text-shadow: 2px 4px 4px rgba(114, 42, 161, 0.6);
}
nav {
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: lavender;
    text-shadow: 2px 4px 4px rgba(190, 177, 199, 0.6);
    height: 10vh;
    color:rgb(192, 134, 192);
    text-align: center;
    font-size: 1.3em;
    border-radius: 5px;
}
.buttons {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 10vh;

}

button {
    color:palevioletred;
    font-size: 1.3em;
    margin-right: 10px;
    font-weight: bold;
    background-color: aliceblue;
    border-radius: 5px;
    text-shadow: 1px 1px 1px rgba(29, 28, 30, 0.6);
}

.disabled {
    color:white;
    background-color: rgb(219, 215, 215);
}
.disabledSelected {
    color:rgb(150, 73, 160);
    background-color: rgb(219, 215, 215);
}

main {
    height: 80vh;
    display: flex;
}
.row {
    display: flex;
    justify-content: space-around;
    align-items: center;
}
.board {
    background-color: white;
    width: 81.3vw;
    height: 81.3vh;
    
}
.score-board {
    display: flexbox;
    text-align: center;
    background-color: rgb(192, 134, 192);
    height: 81.5vh;
    width: 25vw;
    border-radius: 10px;
}
.score{
    background-color: none;
    color:black;
}
.flip-card {
    display: flex;
    justify-content: space-between;
    height: 20vh;
    width: 20vw;
    perspective: 1000px;
}
.card {
    display: flex;
    align-items: center;
    justify-content: center;
    background-color:lightpink;
    border:1px gray solid;
    height: 100%;
    width: 100%;
    text-align: center;
    font-size: 3.5em;
    border-radius: 10px;
    margin: 2px;
    position: relative;
    transition: transform 0.8s;
    transform-style: preserve-3d;
    box-shadow: 0 4px 4px 0 rgba(0,0,0,0.2);
    cursor: pointer;
}

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

.matched {
    transform: rotateY(180deg);
    /* backface-visibility: visible; */
}

.card-front, .card-back{
    display: flex;
    align-items: center;
    justify-content: center;
    position: absolute;
    width:100%;
    height:100%;
    -webkit-backface-visibility: hidden;
    backface-visibility: hidden;
}

.card-front {
    background-color: lavender;
    color:rgb(192, 134, 192);
    text-shadow: 1px 2px 2px rgba(177, 166, 185, 0.6);
}
.card-back {
    text-align: center;
    background-color: #fff;
    color:black;
    transform: rotateY(180deg);
    user-select: none;
}