49-change-animation-timing-with-keywords.html

<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>