css/css-animations/animation-timing-function-004-manual.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Animations Test: animation-timing-function - ease-in-out</title>
<link rel="author" title="Nokia Inc." href="http://www.nokia.com">
<link rel="author" title="Intel" href="http://www.intel.com">
<link rel="reviewer" title="Zhiqiang Zhang" href="mailto:zhiqiang.zhang@intel.com"> <!-- 2015-05-07 -->
<link rel="help" href="https://drafts.csswg.org/css-animations-1/#animation-name">
<link rel="help" href="https://drafts.csswg.org/css-animations-1/#animation-duration">
<link rel="help" href="https://drafts.csswg.org/css-animations-1/#animation-timing-function">
<meta name="flags" content="animated">
<meta name="assert" content="Check that animation-timing-function is set to ease-in-out,
                             animation will start slow, gain acceleration in the middel
                             and again slow down at the end.">
<style>
  div {
    animation-name: sample;
    animation-duration: 10s;
    animation-timing-function: ease-in-out;

    background-color: blue;
    height: 100px;
    width: 100px;
    position: relative;
  }

  @keyframes sample {
    from {
      left: 150px;
    }
    to {
      left: 0px;
    }
  }
</style>
<body>
  <p>
    Test passes if there is a filled blue square with 'Filler Text',
    which starts moving from right to left; initially the animation starts slow,
    gains acceleration in the middle and again slows down at the end.
  </p>
  <div>Filler Text</div>
</body>