3D CSS Code Example

:root {
  --boxcolor: #0ff7;
  --rotate-speed: 30s;
  --bounce-speed: 2s;
}

body {
  background-color: #000;
  min-height: 100vh;
  overflow: hidden;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 75px;
  perspective: 10em;
  perspective-origin: 50% calc(50% - 2em);
}

.scene {
  position: relative;
  transform-style: preserve-3d;
  animation: scene-rotate var(--rotate-speed) infinite linear;

  @keyframes  scene-rotate {
    to { transform: rotateY(360deg); }
  }
}

.ball {
  width: 1em;
  height: 1em;
  border-radius: 50%;
  background: lightblue;

  position: absolute;
  left: -.5em;
  bottom: 1em;
  background-image: radial-gradient(
    circle at top,
    lightblue, 50%, #000
  );
    animation:
    ball-bounce var(--bounce-speed) infinite ease-out,
    scene-rotate var(--rotate-speed) infinite linear reverse;

    @keyframes  ball-bounce {
      0%, 100% { bottom: 0.5em; }
      50%  { bottom: 3em; animation-timing-function: ease-in; }
    }
}

.ball-shadow {
  position: absolute;
  width: 100%;
  height: 100%;
  background-image: radial-gradient(#0007, #0000 50%);

  animation: ball-shadow var(--bounce-speed) infinite ease-out;


  @keyframes  ball-shadow {
    0%, 8%, 93.5%, 100% { transform: scale(1); opacity: 1; }
    50%  { transform: scale(2);
           opacity: 0.5;
           animation-timing-function: ease-in; }
  }
}

.cube {
  width: 2em;
  height: 2em;

  position: absolute;
  bottom: -1em;
  left: -1em;

  animation: cube-height var(--bounce-speed) infinite linear;

  @keyframes  cube-height {
    0%, 100% { height: 1.5em; }
    8%, 93.5%  { height: 2em; }
  }

  .front, .right, .back, .left {
    position: absolute;
    width: 100%;
    height: 100%;
    background: var(--boxcolor);
    box-shadow: 0 0 0.5em #000a inset;
  }

  .front { transform: translateZ(1em); }
  .right { transform: rotateY(90deg) translateZ(1em); }
  .back { transform: rotateY(180deg) translateZ(1em); }
  .left { transform: rotateY(270deg) translateZ(1em); }

  .top {
    position: absolute;
    width: 2em;
    height: 2em;
    background: var(--boxcolor);
    transform: translateY(-50%) rotateX(90deg);
    box-shadow: 0 0 0.5em #000a inset;
  }

  .bottom {
    position: absolute;
    width: 2em;
    height: 2em;
    background: var(--boxcolor);
    filter: brightness(20%);
    bottom: 0;
    transform: translateY(50%) rotateX(90deg);
    box-shadow: 0 0 0.5em #000;
  }

}

.floor {
  position: absolute;
  transform:
    translate(-50%, -50%)
    rotateX(90deg);
    top: 1em;

  width: 15em;
  height: 15em;
  background-image:
    radial-gradient(#0000, #000a 75%),
    repeating-conic-gradient(from 45deg,
                             #111 0deg 90deg,
                             #222 90deg 180deg);
  background-size: 100%, 1em 1em;
}