title: HTML5 canvas create outer glow effect of shape
body: <p>I want to create an outer glow effect for arc shapes in my canvas tag.
  This is what it's supposed to look like:
  <img src="https://i.stack.imgur.com/worKA.jpg" alt="enter image description here"></p>
  
  <p>So far I have the circles in white. I tried using a dropShadow that has an Offset of '0', but this doesn't look right.</p>
  
  <p>What do you suggest? Maybe shapes underneath that have a gradient from blue to black?
  Thanks in advance!</p>
  
  <p>Edit: Finally got it working. Used a for loop to draw circles with different radius and alpha.
  <img src="https://i.stack.imgur.com/0MnEB.jpg" alt="enter image description here"></p>