.heart {
  fill: red;
  // stroke: red;
  position: relative;
  // top: 2px;
  left: 2px;
  width: 10px;
  animation: pulse 1s ease infinite;
}

@keyframes pulse {
  0% { transform: scale(0.7); }     
  50% { transform: scale(1.3); } 
  100% { transform: scale(0.7); }
}