Only use available and valid CSS properties – available properties listed below
Do this:
background-color: blue;
opacity: 0.5;
box-shadow: 0 10px 20px rgba(0,0,0,.13), 0 4px 7px rgba(0,0,0,.2);
Enter them as if you are already inside your selector

Don't do this:
.my-layer {
  background: blue;
  opacity: 0.5;
  box-shadow: 0 10px 20px rgba(0,0,0,.13),0 4px 7px rgba(0,0,0,.2);
}