Learn to Create an SVG Knockout Mask Animation

This tutorial is nice and quick and aims to demystify the transparent knockout mask effect in SVG. Since I started using SVG I've often needed to animate bubbles - don't ask me why but I have and usually they've needed to be the same colour as the background. Until recently I animated bubbles that were the same colour - the problem here is that you have to go through and change all the bubbles' colour again if the background colour changes. No more! By using an SVG mask and placing an animation inside t