html,
body {
    background: #000;
    
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
}

.glow-on-hover {
    width: 220px;
    height: 50px;
    border: none;
    outline: none;
    color: #fff;
    background: #111;
    cursor: pointer;
    position: relative;
    z-index: 0;
    border-radius: 10px;
}

.glow-on-hover:before {
    content: '';
    background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
    position: absolute;
    top: -2px;
    left:-2px;
    background-size: 400%;
    z-index: -1;
    filter: blur(5px);
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    animation: glowing 20s linear infinite;
    opacity: 0;
    transition: opacity .3s ease-in-out;
    border-radius: 10px;
}

.glow-on-hover:active {
    color: #000
}

.glow-on-hover:active:after {
    background: transparent;
}

.glow-on-hover:hover:before {
    opacity: 10;
}

.glow-on-hover:after {
    z-index: -1;
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    background: #111;
    left: 0;
    top: 0;
    border-radius: 10px;
}

container {
  width: 400px;
  height: 400px;
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  display: flex;
  justify-content: center;
  align-items: center;
}

.center {
  width: 180px;
  height: 60px;
  position: absolute;
}

.btn {
  width: 180px;
  height: 60px;
  cursor: pointer;
  background: transparent;
  border: 1px solid #91C9FF;
  outline: none;
  transition: 1s ease-in-out;
}

svg {
  position: absolute;
  left: 0;
  top: 0;
  fill: none;
  stroke: #fff;
  stroke-dasharray: 150 480;
  stroke-dashoffset: 150;
  transition: 1s ease-in-out;
}

.btn:hover {
  transition: 1s ease-in-out;
  background: #4F95DA;
}

.btn:hover svg {
  stroke-dashoffset: -480;
}

.btn span {
  color: white;
  font-size: 18px;
  font-weight: 100;
}

@keyframes glowing {
    0% { background-position: 0 0; }
    50% { background-position: 400% 0; }
    100% { background-position: 0 0; }
}