<a class="blink" href="#">button</a>

body {
	min-height: 100vh;
	margin: 0;
	padding: 10px;
	display: flex;
	justify-content: center;
	align-items: center;
}
a {
	font-weight: 600;
	color: #fff;
	background: #5876a3;
	padding: 10px 20px;
	border-radius: 5px;
	text-decoration: none;
	box-shadow: 0 4px 0 #3f5c88;
}


.blink {
	-webkit-animation: blink 1s ease-in-out infinite alternate;
	animation: blink 1s ease-in-out infinite alternate;
}
@-webkit-keyframes blink {
	0% {opacity: 0;}
	100% {opacity: 1;}
}
@keyframes blink {
	0% {opacity: 0;}
	100% {opacity: 1;}
}