body {
    background-image: url('images/bg.jpg');
    background-size: cover;
}

#content-game {
    height: 100%;
}

.alertify-notifier {
    position: fixed;
    bottom: 20px;
    right: 20px;
    width: 300px;
    font-size: 24px;
}

.container {
    background-color: rgba(255, 255, 255, 0.7);
    width: 100vw;
    height: 90vh;
}

.list-card {
    padding: 5px;
    width: 100%;
    height: 640px;
    margin: auto;
    display: flex;
    flex-wrap: wrap;
    perspective: 1000px;
}

.card {
    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);
}

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

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

.front-face,
.back-face {
    width: 100%;
    height: 100%;
    padding: 5px;
    position: absolute;
    border-radius: 5px;
    background: #1C7CCC;
    backface-visibility: hidden;
    background-image: repeating-linear-gradient(-45deg, rgba(255, 255, 255, 0.25), rgba(255, 255, 255, 0.25) 1px, transparent 1px, transparent 6px);
    box-shadow: 2px 2px 5px rgba(0, 0, 0, 0.3);
    background-color: #3498db;
    font-size: 60px;
    justify-content: center;
    display: flex;
    align-items: center;
}

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

.form-switch .form-check-input:not(:checked)+.form-check-label i.bi-volume-up {
    display: none;
}

.form-switch .form-check-input:checked+.form-check-label i.bi-volume-mute {
    display: none;
}

@media screen and (min-width: 768px) {
    #content-game {
        height: 90vh;
    }

    .front-face,
    .back-face {
        font-size: 120px;
    }
}