html,body,.box {
	height:100%;
	display:flex;
	align-items:center;
	justify-content:center;
}
body {
	background-color:#222;
}
.box {
	font-size:2.5em;
	width:10em;
	height:5em;
	background-color:#111;
	border-radius:0.5em;
	text-align:center;
	line-height:1.5em;
	font-family:sans-serif;
	position:relative;
	animation:animate_text 2s linear infinite alternate;
}
.box::before {
	content:'';
	position:absolute;
	width:calc(100% + 10%);
	height:calc(100% + 20%);
	border-radius:0.5em;
	z-index:-1;
	background-image:linear-gradient(60deg,aquamarine,cornflowerblue,goldenrod,hotpink,salmon,lightgreen,sandybrown,violet);
	background-size:300%;
	animation:animate_bg 5s infinite;
}
@keyframes animate_bg {
	0%,100% {
	background-position:0%,50%;
}
50% {
	background-position:100%,50%;
}
}@keyframes animate_text {
	from {
	color:lime;
}
to {
	color:yellow;
}
}