title: Navigation bar with transparent arrow pointer
body: <p>I am working in an website and I created a navigation bar with an arrow pointing to the active section in the bottom:</p>
  
  <p><img src="https://i.stack.imgur.com/TJiZF.png" alt="enter image description here"></p>
  
  <p>That navigation bar is fixed in the top, and I have a lot of sections with background images and content, I would like to make the arrow transparent to that content <strong>Edit: (to the background image you can see below the navbar)</strong>.</p>
  
  <p>How could I do this?</p>
  
  <p>Thanks! :)</p>