body{
  padding:0;
  margin:0;
}

.container {
  position:relative;
  display:block;
  width: 100vw;
  height: 100vh;
}

.button {
  position:relative;
  left:0%;
  top:0%;
  border-radius: 5px;
  -webkit-animation-name: flash;
  -webkit-animation-duration: 3s;
  -webkit-animation-iteration-count: infinite;
}

@-webkit-keyframes flash{
  /*0%, 100%{background: red;}
  25%{background: yellow;}
  50%{background: green;}
  75%{background: blue;}*/
}