Change Animation Timing with Keywords

Summary

The animation-timing-function property controls how quickly an animated element changes over the duration of the animation.
- The default value ease, starts slow, speeds up in the middle, and then slows down again in the end.
- The value ease-out starts quick, then slows down.
- The value ease-in starts slow, then speeds up.
- The value linear is constant.

Final Code

<style>

  .balls {
    border-radius: 50%;
    background: linear-gradient(
      35deg,
      #ccffff,
      #ffcccc
    );
    position: fixed;
    width: 50px;
    height: 50px;
    margin-top: 50px;
    animation-name: bounce;
    animation-duration: 2s;
    animation-iteration-count: infinite;
  }
  #ball1 {
    left:27%;
    animation-timing-function: linear;
  }
  #ball2 {
    left:56%;
    animation-timing-function: ease-out;
  }

  @keyframes bounce {
    0% {
      top: 0px;
    }
    100% {
      top: 249px;
    }
  }

</style>

<div class="balls" id="ball1"></div>
<div class="balls" id="ball2"></div>