* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #050505;
}

.cube {
    position: relative;
    width: 300px;
    height: 300px;
    transform-style: preserve-3d;
    animation: animate 4s linear infinite;
}

@keyframes animate
{
    0%
    {
        transform: rotateX(-30deg) rotateY(0deg);
    }

    100%
    {
        transform: rotateX(-30deg) rotateY(360deg);
    }
} 

.cube div {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    transform-style: preserve-3d;
}

.cube div span {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(#151515, #00ec00);
    transform: rotateY(calc(90deg * var(--i))) translateZ(150px); /* 300 / 2 */;
}

.top {
    position: absolute;
    top: 0;
    left: 0;
    width: 300px;
    height: 300px;
    background: #222;
    transform: rotateX(90deg) translateZ(150px);    
}

.top::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 300px;
    height: 300px;
    background: #0f0;
    transform: translateZ(-380px);
    filter: blur(20px);
    box-shadow: 0 0 120px rgba(0, 255, 0, 0.2),
    0 0 200px rgba(0, 255, 0, 0.4),
    0 0 300px rgba(0, 255, 0, 0.6),
    0 0 400px rgba(0, 255, 0, 0.8),
    0 0 500px rgba(0, 255, 0, 1);
}