https://codepen.io/lokesh/pen/YzzKzva

I cant find a way to make it work on firefox

    #cursor {
  position: fixed;
  top: calc(var(--cursor-size) * -0.5);
  left:  calc(var(--cursor-size) * -0.5);
  pointer-events: none;
  mix-blend-mode: difference;  
  filter: url(#goo);
}

im adding this just so i can post it