Affinity Photo Radial Gradient Mask

First off, this is in no way intended to be a "professional" quality tutorial. After poking around in Affinity Photo for entirely too long, I figured out how to do this, so I posted this video for my own reference. If you find it helpful, that's awesome. This is a brief example of how to create a radial gradient mask (or any type of gradient mask) that can have any number of adjustment layers or live filters applied to it. It works similar to the "Selective" tool in Snapseed.