@keyframes smoke {
  0% {opacity: 0.2; transform: translateY(0) scale(1);}
  50% {opacity: 0.5; transform: translateY(-20px) scale(1.05);}
  100% {opacity: 0.2; transform: translateY(0) scale(1);}
}

.smoke {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: url('https://pngimg.com/uploads/smoke/smoke_PNG5525.png') center center no-repeat;
  background-size: contain;
  animation: smoke 5s infinite ease-in-out;
  pointer-events: none;
  z-index: 2;
}