JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div id="my-div"></div>
</body>

CSS

#my-div{    
    position:absolute;
    top: 50px;
    left: 50px;
    height: 100px;
    width:  100px;
    background-color: #eee;
    animation: shadowThrob 5s;
    animation-direction: alternate;
    -webkit-animation: shadowThrob 5s;
    -webkit-animation-direction: alternate;
}
/* Standard syntax */
@keyframes shadowThrob {
	from {box-shadow: 0 0 30px 10px rgba(190,65,12, 0.9);}
	to {box-shadow: 0 0 30px 10px rgba(190,65,12, 0.2);}
}
/* Standard syntax */
/* Chrome, Safari, Opera */
@-webkit-keyframes shadowThrob {
	from {box-shadow: 0 0 30px 10px rgba(190,65,12, 0.9);}
	to {box-shadow: 0 0 30px 10px rgba(190,65,12, 0.2);}
}