Animated Button With Siren Animation

Css

body {
  display: -webkit-box;
  display: flex;
  -webkit-box-pack: center;
          justify-content: center;
  -webkit-box-align: center;
          align-items: center;
  min-height: 100vh;
  background: #eeeeee;
}

.button {
  position: relative;
  -webkit-appearance: none;
     -moz-appearance: none;
          appearance: none;
  padding: 1em 2em;
  color: white;
  font-size: 1.2em;
  cursor: pointer;
  outline: none;
  overflow: hidden;
  border: none;
  border-radius: 10px;
  text-transform: uppercase;
  font-weight: bold;
  -webkit-animation: example 0.5s linear  infinite alternate;
          animation: example 0.5s linear  infinite alternate;
}

@-webkit-keyframes example {
  from {
    background: -webkit-gradient(linear, left top, right top, from(#ff0000), to(#3f7fff));
    background: linear-gradient(to right, #ff0000 0%, #3f7fff 100%);
  }
  to {
    background: -webkit-gradient(linear, left top, right top, from(#3f7fff), to(#ff0000));
    background: linear-gradient(to right, #3f7fff 0%, #ff0000 100%);
  }
}

@keyframes example {
  from {
    background: -webkit-gradient(linear, left top, right top, from(#ff0000), to(#3f7fff));
    background: linear-gradient(to right, #ff0000 0%, #3f7fff 100%);
  }
  to {
    background: -webkit-gradient(linear, left top, right top, from(#3f7fff), to(#ff0000));
    background: linear-gradient(to right, #3f7fff 0%, #ff0000 100%);
  }
}

Html

<button class="button">
	<span>reporting</span>
</button>

DEMO