Css3 Animation 动画原则六

<h1>Principle 6: Slow in and Slow out</h1>
<h2><a href="https://cssanimation.rocks/principles/" target="_parent">Animation Principles for the Web</h2>
 <article class="principle six">
    <div class="shape a"></div>
</article>

.six .shape {
  animation: six 3s infinite cubic-bezier(0.5,0,0.5,1);
}

@keyframes six {
  0%, 5% {
    transform: translate(-12em);
  }
  45%, 55% {
    transform: translate(12em);
  }
  95%, 100% {
    transform: translate(-12em);
  }
}

/* General styling */
body {
  margin: 0;
  background: #e9b59f;
  font-family: HelveticaNeue, Arial, Sans-serif;
  color: #fff;
}

h1 {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  text-align: center;
  font-weight: 300;
}

h2 {
  font-size: 0.75em;
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  text-align: center;
}

a {
  text-decoration: none;
  color: #333;
}

.principle {
  width: 100%;
  height: 100vh;
  position: relative;
}

.shape {
  background: #2d97db;
  border: 1em solid #fff;
  width: 4em;
  height: 4em;
  position: absolute;
  top: calc(50% - 2em);
  left: calc(50% - 2em);
}