The essence of a marble structure is to regard a game-location including the characters present as placeholders for clues.
Like a marble in a closed bag of marbles are the clues hidden from view.
Every encounter either with the environment
like character(not player), objects, piece of scenography or even a view of the landscape that gives the player a clue on how to solve a prewritten puzzle or mystery.
The trick is that a player would need a minimum number of clues before being able to realize the hidden truth.
(compared to fates that explains everything:)