.bidyapan3D {
    perspective: 800px;
    display: flex;
    align-items: center;
    justify-content: center;

}

.cube {
    transform-style: preserve-3d;
    position: relative;
    width: 300px;
    height: 300px;
    -webkit-animation: rotate 20s ease-in-out infinite;
    animation: rotate 20s ease-in-out infinite;
    transform-origin: center center;
}

.side {
    position: absolute;
    width: 300px;
    height: 300px;
    background-color: #333;
    opacity: 0.95;
    background-size: cover;
    background-repeat: no-repeat;
}

@-webkit-keyframes rotate {
    0% {
        transform: rotateY(0);
    }
    100% {
        transform: rotateY(360deg);
    }
}

@keyframes rotate {
    0% {
        transform: rotateY(0);
    }
    100% {
        transform: rotateY(360deg);
    }
}