Animated button border

by kthornbloom

HTML

<a href="#" class="outline">
<div>BUTTON</div>
</a>

CSS

body {
  background: #000;
  font-family: sans-serif;
}

.outline {
  display: inline-block;
  color: #fff;
  text-decoration: none;
  position: relative;
  padding: 1px;
  overflow: hidden;
  border-radius: 50px;
  > div {
    background: linear-gradient(40deg, #000, #222);
    border-radius: 50px;
    padding: 1rem 4rem;
    font-size: 14px;
  }
}

.outline::before {
  content:'';
  position: absolute;
  width: 100%;
  aspect-ratio: 1/1;
  display: block;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  background: conic-gradient(#ffffff20 160deg, #ffffff, #ffffff20 200deg);
  z-index: -1;
  animation: spin 5s infinite linear;
}

@keyframes spin {
  0% {
    transform: translateY(-50%) rotate(0deg);
  }
  25% {
    transform: translateY(-50%) rotate(90deg);
    animation-timing-function: ease-out;
  }
  50% {
    transform: translateY(-50%) rotate(180deg);
    animation-timing-function: ease-in;
  }
  75% {
    transform: translateY(-50%) rotate(270deg);
    animation-timing-function: ease-out;
  }
  100% {
    transform: translateY(-50%) rotate(360deg);
    animation-timing-function: ease-in;
  }
}