<div class="container">	
	<div class="btn">
		<span>Atom</span>
		<div class="dot"></div>
	</div>
	<h1>&#x261D; Hover on the button &#x261D;</h1>
</div>

:root {
	--bg: #3C465C;
	--primary: #78FFCD;
	--solid: #fff;
	--btn-w: 10em;
	--dot-w: calc(var(--btn-w)*.2);
	--tr-X: calc(var(--btn-w) - var(--dot-w));
}
* {box-sizing: border-box;}
*:before, *:after {box-sizing: border-box;}

body {
	height: 100vh;
	display: flex;
	justify-content: center;
	align-items: center;
	flex-flow: wrap;
	background: var(--bg);
	font-size: 20px;
	font-family: 'Titillium Web', sans-serif;
}
h1 {
	color: var(--solid);
	font-size: 2.5rem;
	margin-top: 6rem;	
}
.btn {
	position: relative;
	margin: 0 auto;
	width: var(--btn-w);
	color: var(--primary);
	border: .15em solid var(--primary);
	border-radius: 5em;
	text-transform: uppercase;
	text-align: center;
	font-size: 1.3em;
	line-height: 2em;
	cursor: pointer;	
}
.dot {
	content: '';
	position: absolute;
	top: 0;
	width: var(--dot-w);
	height: 100%;
	border-radius: 100%;
	transition: all 300ms ease;
	display: none;
}
.dot:after {
	content: '';
	position: absolute;
	left: calc(50% - .4em);
	top: -.4em;
	height: .8em;
	width: .8em;
	background: var(--primary);
	border-radius: 1em;
	border: .25em solid var(--solid);
	box-shadow: 0 0 .7em var(--solid),
				0 0 2em var(--primary);
}
.btn:hover .dot,
.btn:focus .dot {
	animation: atom 2s infinite linear;
	display: block;
}
@keyframes atom {
	0% {transform: translateX(0) rotate(0);}
	30%{transform: translateX(var(--tr-X)) rotate(0);}
	50% {transform: translateX(var(--tr-X)) rotate(180deg);}
	80% {transform: translateX(0) rotate(180deg);}
	100% {transform: translateX(0) rotate(360deg);}
}