so Steam games can give you achievements.1 They can also take achievements away.2 And they can check what achievements you have.3 There is evidently also no requirement that every achievement in a game needs to be legitimately obtainable,4 and if there is a limit to how many achievements a single game can have, it's probably in the thousands.5 This implies that Steam achievements could be used as an inventory system where every item in the game is a Steam achievement and the item pickup notification in-game is just the global Steam achievement notification. Alternatively, a game could use a couple thousand arbitrary achievements to store a few kilobytes of particularly persistent save data. This is probably a terrible idea but I want to see it done if only because I think people who care about getting 100% of the achievements deserve a properly interesting challenge.
1: like, every game on Steam
2: eating a certain item in Diaries of a Spaceport Janitor has a chance of removing all your achievements, except for a certain achievement which you only get by eating that item and having it remove all your other achievements.
3: A Dance of Fire and Ice has an option in the settings to recover your save data from your Steam achievements, because it awards a Steam achievement for most things it saves.
4: The Stanley Parable and Where the Water Tastes Like Wine both have intentionally unobtainable achievements. Not to mention many games where the achievements are bugged, or awarded for limited-time events that cannot happen again, etc.
5: Apparently a limit of 5000 was imposed a few years ago. LOGistICAL has 9821 and may have been grandfathered in. Most of the (slightly infamous) "Zup!" games have around 500, but Zup! X has 2880; almost all of these achievements are nearly exact duplicates, which also demonstrates that meaningless achievements are totally permissable.
