Code Samples:

HTML

<div class="bouncing-loader">
  <div></div>
  <div></div>
  <div></div>
</div>

CSS

@keyframes bouncing-loader {
  to {
    opacity: 0.1;
    transform: translate3d(0, -1rem, 0);
  }
}
.bouncing-loader {
  display: flex;
  justify-content: center;
}
.bouncing-loader > div {
  width: 1rem;
  height: 1rem;
  margin: 3rem 0.2rem;
  background: #8385aa;
  border-radius: 50%;
  animation: bouncing-loader 0.6s infinite alternate;
}
.bouncing-loader > div:nth-child(2) {
  animation-delay: 0.2s;
}
.bouncing-loader > div:nth-child(3) {
  animation-delay: 0.4s;
}

Brief Explanation:

1. @keyframes defines an animation that has two states, where the element changes opacity and is translated up on the 3D plane using transform: translate3d(). Using a single axis translation on transform: translate3d() improves the performance of the animation.

2. .bouncing-loader is the parent container of the bouncing circles and uses display: flex and justify-content: center to position them in the center.

3. .bouncing-loader > div, targets the three child divs of the parent to be styled. The divs are given a width and height of 1rem, using border-radius: 50% to turn them from squares to circles.

4. margin: 3rem 0.2rem specifies that each circle has a top/bottom margin of 3rem and left/right margin of 0.2rem so that they do not directly touch each other, giving them some breathing room.

5. animation is a shorthand property for the various animation properties: animation-name, animation-duration, animation-iteration-count, animation-direction are used.

6. nth-child(n) targets the element which is the nth child of its parent.

7. animation-delay is used on the second and third div respectively, so that each element does not start the animation at the same time.

Note: 1rem is usually 16px.

Thanks for reading...

Happy Coding!