breathing cube

HTML

<div></div>

CSS

div
{
  width:100px;
  height:100px;
  border-radius: 50%;
  background:orange;

  display: inline-block;
  animation: fade 10s forwards;
  -webkit-animation: fade 10s forwards;
  -moz-animation: fade 10s forwards;
  -o-animation: fade 10s forwards;
  animation-iteration-count: infinite;
  -webkit-animation-iteration-count: infinite;
  -moz-animation-iteration-count: infinite;  
  -o-animation-iteration-count: infinite;
}

@keyframes fade {
20%   {width:300px;height:300px}
50%   {width:100px;height:100px}
100% {width:300px;height:300px}
}

@-webkit-keyframes fade {
20%   {opacity:0;}
50%   {opacity:1;}
100% {opacity:0;}
}

@-moz-keyframes fade {
20%   {width:100px;height:100px;margin-top:0px;margin-left:0px;}
50%   {width:50px;height:50px;margin-top:25px;margin-left:25px;}
100% {width:100px;height:100px;margin-top:0px;margin-left:0px;}
}

@-o-keyframes fade {
20%   {opacity:0;}
50%   {opacity:1;}
100% {opacity:0;}
}