<div class="card-15">
  <div class="card-15__inner">
    <span class="card-15__tag">Color</span>
    <h4 class="card-15__title">Gradient Rotate</h4>
    <p class="card-15__body">Border hue-rotates continuously on hover.</p>
  </div>
</div>

.card-15__tag {
  font-family: monospace;
  font-size: 10px;
  padding: 2px 8px;
  border-radius: 20px;
  background: rgba(124, 108, 255, 0.15);
  color: #7c6cff;
  border: 1px solid rgba(124, 108, 255, 0.3);
  display: inline-block;
  margin-bottom: 10px;
}
.card-15__title {
  font-size: 17px;
  font-weight: 700;
  color: #f0eeff;
  margin-bottom: 6px;
}
.card-15__body {
  font-size: 13px;
  color: #b8b6d4;
  line-height: 1.6;
}
.card-15 {
  width: 100%;
  max-width: 280px;
  border-radius: 14px;
  padding: 2px;
  cursor: pointer;
  background: rgba(255, 255, 255, 0.05);
  transition: background 0.3s;
}
.card-15:hover {
  background: conic-gradient(#7c6cff, #ff6c8a, #3de8f5, #1ed98a, #7c6cff 360deg);
  animation: card-15-spin 4s linear infinite;
}
@keyframes card-15-spin {
  to { filter: hue-rotate(360deg); }
}
.card-15__inner {
  border-radius: 12px;
  padding: 22px;
  background: #17171f;
}