Dynamic Gradient Border Animation

HTML

CSS

* {
  box-sizing: border-box;
}
body {
  margin: 0;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: #0e0e16;
  font-family: 'Poppins', sans-serif;
}
.card {
  position: relative;
  width: 300px;
  height: 200px;
  background: #111;
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 20px;
  overflow: hidden;
  font-size: 1.2rem;
  text-align: center;
}
.card::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: 20px;
  padding: 3px;
  background: linear-gradient(120deg,
    #ff0077, #ff7b00, #ffd300, #00ff88, #00aaff, #a000ff, #ff0077);
  background-size: 400% 400%;
  -webkit-mask:
    linear-gradient(#fff 0 0) content-box,
    linear-gradient(#fff 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  animation: borderMove 6s linear infinite;
}
@keyframes borderMove {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}
.content {
  position: relative;
  z-index: 1;
  padding: 20px;
}