What gameplay systems or game mechanics do you enjoy?

I'm not sure if this counts as gameplay mechanics or rather narrative structure, but games like Outer Wilds, Fez, Tunic, where the exploration and discovery of the game is the end goal of playing the game, not just getting to the game's end state.

I'm not sure if there's an accepted term for these games, but I've always thought of them as "archaeology" games. There's a bunch of stuff, both plot and gameplay, that is hidden (sometimes in plain sight), until you discover it and find out what meaning it carries.