body {
margin:0;
padding:0;
background:#000;
}
.shadow {
position:relative;
margin:200px auto 0;
width:400px;
height:250px;
background:linear-gradient(0deg,#000,#262626);
}
.shadow:before,
.shadow:after {
content:'';
position:absolute;
top:-2px;
left:-2px;
background:linear-gradient(45deg,#fb0094,#0000ff,#00ff00,#ffff00,#ff0000,#fb0094,#0000ff
,#00ff00,#ffff00,#ff0000);
background-size:400%;
width:calc(100% + 4px);
height:calc(100% + 4px);
z-index:-1;
animation:animate 20s linear infinite;
}
.shadow:after {
filter:blur(20px);
}
@keyframes animate {
0% {
background-position:0 0;
}
50% {
background-position:300% 0;
