Subscriber-Only: Today's episode is available only to subscribers. If you are a Point-Free subscriber you can access your private podcast feed by visiting https://www.pointfree.co/account.---We can now persist simple bits of state to user defaults using the @Shared property wrapper, but there is more work to be done. We need to observe changes to user defaults in order to play those changes back to @Shared, and we need to put in a bit of extra work to make everything testable.