#container {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
}

.card,
.frontside {
    transform-style: preserve-3d;
    transition: all .5s;
}

.frontside {
    width: 230px;
    height: 290px;
    padding: 15px;
    margin: 15px;
    text-align: center;
    border-radius: 15px;
    border: 3px solid teal;
    box-shadow: 0 0 10px #000;
    background-color: #000;
    position: relative;
}

.frontside:hover {
    cursor: pointer;
}

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

h1 {
    font-size: 1.7em;
    color: #fff;
}

img {
    width: 100px;
    height: 100px;
}

#green {
    color: green;
}

#red {
    color: red;
}