How do I move a box shadow on top of an image

Question

I've added a box shadow successfully and moved the image to check, yet when the image is in place, it covers the box shadow, how would I make the box shadow over the image?

Here is the CSS

  nav {
  background-color: #404040;
  width:100%;
  height:20px;
  padding:15px;
  word-spacing: 10px;
 box-shadow: -5px 10px 10px -3px black;
}

img {
  width:111.6%;
  height:200px;
  margin-left: -10px;
  margin-top: 100px;
} 

Answer 1

Never mind, just found out about z index and how that works so now I'm good :)