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HTML 

              
                <div class="outer">
  <div class="outer_scene">
    <div class="outer_floor"></div>
    <div class="balls">
      <div class="ball"></div>
      <div class="ball"></div>
      <div class="ball"></div>
      <div class="ball"></div>
    </div>
  </div>
</div>

<div class="portal">
  <div class="portal_scene">
    <div class="portal_floor"></div>

    <div class="cube">
      <div class="cube_shadow"></div>
      <div class="cube_body">
        <div></div><div></div><div></div><div></div><div></div><div></div>
      </div>
    </div>
    <div class="cube">
      <div class="cube_shadow"></div>
      <div class="cube_body">
        <div></div><div></div><div></div><div></div><div></div><div></div>
      </div>
    </div>
    <div class="cube">
      <div class="cube_shadow"></div>
      <div class="cube_body">
        <div></div><div></div><div></div><div></div><div></div><div></div>
      </div>
    </div>
    <div class="cube">
      <div class="cube_shadow"></div>
      <div class="cube_body">
        <div></div><div></div><div></div><div></div><div></div><div></div>
      </div>
    </div>
  </div>
</div>

<div class="outer">
  <div class="outer_scene">
    <div class="balls">
      <i></i>
      <i></i>
      <i></i>
      <i></i>
      <div class="ball"></div>
      <div class="ball"></div>
      <div class="ball"></div>
      <div class="ball"></div>
    </div>
  </div>
</div>
!

CSS 

              
                *, *::before, *::after {
  padding: 0;
  margin: 0 auto;
  box-sizing: border-box;
}

body {
  background-color: #def;
  background-image: linear-gradient(#201, #001 50%);
  color: #fff;
  min-height: 100vh;
  display: grid;
  place-items: center;
  overflow: hidden;

  *:not(:empty), * {
    transform-style: preserve-3d;
  }
}

$speed: 9s;
$speed2: 4s;
$rAngle: 50deg;

.outer {
  position: absolute;
  top: 50%; left: 50%;
  perspective: 800px;

  &_scene {
    position: absolute;
    top: 50%; left: 50%;
    animation: sceneRotate $speed infinite ease-in-out alternate;
  }

  &_floor {
    position: absolute;
    top: 50%; left: 50%;
    width: 3200px; height: 3200px;
    transform: translate(-50%, -50%) rotateX(90deg) translateZ(-240px);
    background-color: #07a;
    background-image:
      radial-gradient(#111a, #1110, #001 60%),
      radial-gradient(#fff5 0, #fff0 15px);
    background-size: 100%, 30px 30px;
  }
}

.ball {
  position: absolute;
  top: 240px;
  width: 0; height: 0;
  transform-style: preserve-3d;
  animation: ballAngle $speed infinite ease-in-out alternate;

  $count: 8;
  @for $i from 0 to $count {
    &:nth-child(#{$i + 1}) {
      --ry: #{360deg / $count * $i + 112.5deg};
      --delay: #{$speed2 / $count * $i * -3};
      --hue: #{$i * 40};
    }
  }

  @keyframes ballAngle {
    from { transform: rotateY(var(--ry, 0)) translateZ(420px) rotateY(calc(var(--ry, 0) * -1)) rotateY($rAngle); }
    to   { transform: rotateY(var(--ry, 0)) translateZ(420px) rotateY(calc(var(--ry, 0) * -1)) rotateY($rAngle * -1); }
  }

  &::before {
    content: '';
    position: absolute;
    left: -120px; top: -120px;
    width: 240px; height: 240px;
    background-image: radial-gradient(#000, #0000 50%);
    animation: ballShadow $speed2 var(--delay, 0s) infinite;

    @keyframes ballShadow {
      0%, 50%, 100% { transform: rotateX(90deg) translateZ(1px) scale(1); opacity: 0.5; animation-timing-function: ease-out; }
      55%, 97% { transform: rotateX(90deg) translateZ(1px) scale(0.9); opacity: 0.5; animation-timing-function: ease-out; }
      75% { transform: rotateX(90deg) translateZ(1px) scale(2); opacity: 0; animation-timing-function: ease-in; }
      94% { transform: rotateX(90deg) translateZ(1px) scale(1.2); opacity: 0.5; animation-timing-function: ease-out; }
    } 
  }

  &::after {
    content: '';
    position: absolute;
    left: -60px; bottom: 0; 
    width: 120px; height: 120px;
    background-image: radial-gradient(circle at top, hsl(0, 100%, 75%), hsl(0, 100%, 0%));
    border-radius: 50%;
    transform-origin: bottom;
    animation: ballJump $speed2 var(--delay, 0s) infinite;

    @keyframes ballJump {
      0%, 50%, 100% { transform: scaleY(1) translateY(0px); animation-timing-function: ease-out; }
      55%, 97% { transform: scaleY(0.8) translateY(0px); animation-timing-function: ease-out; }
      75% { transform: scaleY(1) translateY(-420px); animation-timing-function: ease-in; }
      94% { transform: scaleY(1.2) translateY(0px); animation-timing-function: ease-out; }
    } 
  }
}

.portal {
  position: absolute;
  top: 50%; left: 50%;
  width: 420px; height: 420px;
  background-image: linear-gradient(#201, #000 50%);
  border-radius: 50%;
  box-shadow: 0 0 20px #f77, 0 0 50px #7ff;
  perspective: 660px;
  overflow: hidden;
  animation: portalRotate $speed infinite ease-in-out alternate;

  @keyframes portalRotate {
    from { transform: translate(-50%, -50%) rotateY($rAngle); }
    to { transform: translate(-50%, -50%) rotateY($rAngle * -1); }
  }

  &_scene {
    position: absolute;
    top: 50%; left: 50%;
    animation: sceneRotate $speed infinite ease-in-out alternate;

    @keyframes sceneRotate {
      from { transform: rotateY($rAngle * -1); }
      to { transform: rotateY($rAngle); }
    }    
  }

  &_floor {
    position: absolute;
    top: 50%; left: 50%;
    width: 3200px; height: 3200px;
    transform: translate(-50%, -50%) rotateX(90deg) translateZ(-240px);
    background-color: #444;
    background-image:
      radial-gradient(#111a, #1110, #000 60%),
      repeating-linear-gradient(#fff5 0 5px, #fff0 0 75px),
      repeating-linear-gradient(90deg, #fff5 0 5px, #fff0 0 75px);    
  }
}

.cube {
  position: absolute;
  top: 240px;
  transform: rotateY(var(--ry, 0)) translateZ(525px) rotateY(calc(var(--ry, 0) * -1));

  $count: 4;
  @for $i from 0 to $count {
    &:nth-child(#{$i + 2}) {
      --ry: #{180deg / $count * $i + 112.5deg};
      --delay: #{$speed2 / $count * $i * -1.5};
    }
  }

  &_body {
    position: absolute;
    left: -60px;
    width: 120px; height: 120px;
    transform-origin: bottom;
    animation:
      cubeBottom $speed2 var(--delay, 0s) infinite,
      cubeRotate $speed2 var(--delay, 0s) infinite;

    @keyframes cubeBottom {
      0%, 55%, 94%, 100% { bottom: 0px; animation-timing-function: ease-out; }
      75% { bottom: 420px; animation-timing-function: ease-in; }
    }

    @keyframes cubeRotate {
      0%, 50% { transform: scaleY(1) rotateY(0deg); animation-timing-function: ease-out; }
      55%     { transform: scaleY(0.8) rotateY(0deg); animation-timing-function: ease-in; }
      75%     { transform: scaleY(1) rotateY(240deg); animation-timing-function: ease-out; }
      94%     { transform: scaleY(1.2) rotateY(360deg); }
      97%     { transform: scaleY(0.8) rotateY(360deg); }
      100%    { transform: scaleY(1) rotateY(360deg); }
    }

    & > div {
      position: absolute;
      inset: 0;
      background-color: #fff;
      box-shadow:
        0 0 20px hsl(180, 100%, 25%) inset,
        0 0 50px hsl(180, 100%, 75%) inset;
      opacity: 0.8;

      &:nth-child(1) { transform: translateZ(60px); }
      &:nth-child(2) { transform: rotateY(90deg) translateZ(60px); }
      &:nth-child(3) { transform: rotateY(180deg) translateZ(60px); }
      &:nth-child(4) { transform: rotateY(270deg) translateZ(60px); }
      &:nth-child(5) { transform: rotateX(90deg) translateZ(60px); }
      &:nth-child(6) { transform: rotateX(270deg) translateZ(60px); }
    }
  }

  &_shadow {
    position: absolute;
    left: -70px; top: -70px;
    width: 140px; height: 140px;
    background-color: #0005;
    transform: rotateX(90deg) translateZ(1px);
    filter: blur(20px);
    animation: cubeShadow $speed2 var(--delay, 0s) infinite;

    @keyframes cubeShadow {
      0%, 50% { transform: rotateX(90deg) translateZ(1px) scaleY(1) rotateZ(0deg); opacity: 1; animation-timing-function: ease-out; }
      55%     { transform: rotateX(90deg) translateZ(1px) scaleY(0.8) rotateZ(0deg); opacity: 1; animation-timing-function: ease-in; }
      75%     { transform: rotateX(90deg) translateZ(1px) scaleY(3) rotateZ(-240deg); opacity: 0.4; animation-timing-function: ease-out; }
      94%     { transform: rotateX(90deg) translateZ(1px) scaleY(1.2) rotateZ(-360deg); opacity: 1; }
      97%     { transform: rotateX(90deg) translateZ(1px) scaleY(0.8) rotateZ(-360deg); opacity: 1; }
      100%    { transform: rotateX(90deg) translateZ(1px) scaleY(1) rotateZ(-360deg); opacity: 1; }
    }
  }
}
!

JS
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