Gradient Border

<div class="gradient-border-element">
  <span>Gradient Border</span>
</div>

.gradient-border-element {
  position: relative;
  width: 250px;
  height: 150px;
  padding: 4px;
  display: flex;
  justify-content: center;
  align-items: center;
  border-radius: 8px;
  background: linear-gradient(45deg, #ff416c, #ff4b2b, #ff9100, #ffdd00, #2de2e6, #00b1d2);
  background-size: 300% 300%;
  animation: gradient-shift 6s ease infinite;
}

.gradient-border-element::before {
  content: '';
  position: absolute;
  inset: 4px;
  background: white;
  border-radius: 5px;
  z-index: 0;
}

.gradient-border-element span {
  position: relative;
  z-index: 1;
  font-size: 18px;
  font-weight: 600;
  color: #333;
}

@keyframes gradient-shift {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

/* Dark mode styles */
@media (prefers-color-scheme: dark) {
  .gradient-border-element::before {
    background: #222;
  }
  
  .gradient-border-element span {
    color: #fff;
  }
}