body {
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-image: url('fondo.jpg');
	background-size: cover;
    background-position: center;
}

.invitation-container {
    position: relative;
    width: 390px;
    height: 600px;
    overflow: hidden;
    perspective: 1000px;
}

.side {
    position: absolute;
    top: 0;
    width: 100%;
    height: 100%;
    transform-origin: left;
    transform-style: preserve-3d;
    transition: transform 0.7s;
}

#left-side {
    z-index: 2;
}

#right-side {
    z-index: 1;
    transform-origin: right;
}

.interior {
    position: absolute;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: white;
    z-index: 0;
}

img {
    width: 100%;
    height: 100%;
    display: block;
}

.hidden {
    display: none;
}

@media (max-width: 400px) {
    .invitation-container {
        width: 100vw;
        height: 100vh;
    }
}