.crshadow {
  color: white;
  text-align: center;
  position: relative;
  margin: 200px auto;
  width: 500px;
  height: 400px;
  background: linear-gradient(0deg,#000,#262626);
}

.crshadow > h1 {
  position: absolute;
  top: 25%;
  left: 25%;
}

.crshadow > h1 > i {
  color: #ff0000;
  font-size: 40px;
}

.crshadow:before, .crshadow:after {
  content: '';
  position: absolute;
  top: -2px;
  left: -2px;
  background: linear-gradient(45deg,#fb0094,#ed1c24,#9a0e05,#8b0c0c,#ff0000,#fb0000,#d30707,#f40d0d,#ffffa2,#ff0000,#fb0094,#a21111,#d20a0a,#c31d12,#ff0000,#fb0094,#d00000,#fb2e2e,#f75f55,#ff0000);
  width: calc(100% + 5px);
  height: calc(100% + 5px);
  background-size: 500%;
  z-index: -1;
  animation: cranimate 20s linear infinite;
}

.crshadow:after {
  filter: blur(20px);
}

@keyframes cranimate {
  0% {
    background-position: 0 0;
  }
  50% {
    background-position: 400% 0;
  }
  75% {
    background-position: 200% 0;
  }
  100% {
    background-position: 0 0;
  }
}