How should I organise my plist? I'm creating a game where the player can unlock worlds, where they can unlock levels within those worlds, each levels has a highscore, and so on.

I was wondering in which way should I store this data?  I was originally thinking of making a number of separate plist files, but that seems like an approach which could end up spiralling out of control.

Has anyone approached this problem and come up with a decent solution?
Most apps like that store data in a SQLite3 database rather than property lists. I recommend this route instead—actual implementation/etc is off-topic here.