tvOS Save Game State?

I have a game app, it has 300 levels, and I need to store (for each level) 2 states

  1. has this level been attempted?
  2. if it has been attempted, was it completed

tvOS under Swift (without using iCloud) is limited in what/where it is allowed to permentaly store things.
So I am basicly limited to UserDefaults

The only idea I have had so far is to create a 300 character string with each character position being a letter that indicates the current state

Anyone have a better one?

I can do it with only two Integer values

  1. the highest level available. A level cannot be attempted until all levels below are completed
  2. the highest level complete. This would usually be “available” - 1