body {
  background: #16161d;
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100vw;
  height: 100vh;
}
.button, .shadow {
  width: 300px;
  height: 60px;
  font-size: 1.25rem;
  text-align: center;
  line-height: 60px;
  color: rgba(255,255,255,0.9);
  border-radius: 50px;
  background: linear-gradient(-45deg, #ffa63d, #ff3d77, #338aff, #3cf0c5);
  background-size: 600%;
  -webkit-animation: anime 10s linear infinite;
          animation: anime 10s linear infinite;
}
.shadow {
  position: absolute;
  margin-top: 20px;
  z-index: -1;
  -webkit-filter: blur(20px);
          filter: blur(20px);
  opacity: 0.66;
}
a {
  color: #ffffff;
  text-decoration: none;
}
@-webkit-keyframes anime {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}
@keyframes anime {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}