.cube-loader {
  position: relative;
/* u can choose any size */
  width: 75px;
  height: 75px;
  transform-style: preserve-3d;
  transform: rotateX(-30deg);
  animation: animate 4s linear infinite;
}

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

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

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

.cube-loader .cube-wrapper .cube-span {
  position: absolute;
  width: 100%;
  height: 100%;
  /* top: 0;
  left: 0; */
                                     /* width 75px / 2 = 37.5px */
  transform: rotateY(calc(90deg * var(--i))) translateZ(37.5px);
  background: linear-gradient(
    to bottom,
    hsl(330, 3.13%, 25.1%) 0%,
    hsl(177.27, 21.71%, 32.06%) 5.5%,
    hsl(176.67, 34.1%, 36.88%) 12.1%,
    hsl(176.61, 42.28%, 40.7%) 19.6%,
    hsl(120, 40%, 50%) 27.9%,
    hsl(45, 40%, 50%) 36.6%,
    hsl(240, 40%, 50%) 45.6%,
    hsl(60, 40%, 50%) 54.6%,
    hsl(150, 40%, 50%) 63.4%,
    hsl(300, 40%, 50%) 71.7%,
    hsl(75, 40%, 50%) 79.4%,
    hsl(210, 40%, 50%) 86.2%,
    hsl(15, 40%, 50%) 91.9%,
    hsl(330, 40%, 50%) 96.3%,
    hsl(90, 40%, 50%) 99%,
    hsl(180, 40%, 50%) 100%
  );
}

.cube-top {
  position: absolute;
  width: 75px;
  height: 75px;
  background: hsl(330, 3.13%, 25.1%) 0%;
                      /* width 75px / 2 = 37.5px */
  transform: rotateX(90deg) translateZ(37.5px);
  transform-style: preserve-3d;
}

.cube-top::before {
  content: '';
  position: absolute;
/* u can choose any size */
  width: 75px;
  height: 75px;
  background: hsl(176.61, 42.28%, 40.7%) 19.6%;
  transform: translateZ(-90px);
  filter: blur(10px);
  box-shadow: 0 0 10px #323232,
              0 0 20px hsl(176.61, 42.28%, 40.7%) 19.6%,
              0 0 30px #323232,
              0 0 40px hsl(176.61, 42.28%, 40.7%) 19.6%;
}