<label class="radikalwp-cb-heart"><input type="checkbox" /><span>♥<//span><//label>

.radikalwp-cb-heart input { display: none; }
.radikalwp-cb-heart span {
  font-size: 30px;
  color: #cbd5e1;
  cursor: pointer;
  transition: color .25s ease, transform .3s cubic-bezier(.3, 1.8, .5, 1);
  display: inline-block;
  line-height: 1;
}
.radikalwp-cb-heart input:checked + span {
  color: #ef4444;
  animation: radikalwp-cb-heart-pop .45s cubic-bezier(.3, 1.8, .5, 1);
}
@keyframes radikalwp-cb-heart-pop {
  0% { transform: scale(.6); }
  55% { transform: scale(1.35); }
  100% { transform: scale(1); }
}