title: Google polygonal map background color transparent, surrounding area semi-transparent overlay
body: <p>I'm trying to replicate something similar to the following map, where the polygonal area is transparent and the surrounding area is semi-transparent:</p>
  
  <p><img src="https://i.stack.imgur.com/RaRD2.png" alt="enter image description here"></p>
  
  <p>Can anyone help with this?</p>
  
  <p>Here's the original:
  <a href="https://energyeasy.ue.com.au/outages/powerOutages" rel="nofollow noreferrer">https://energyeasy.ue.com.au/outages/powerOutages</a></p>