I’ve been doing some thinking recently, about hidden information, and how games use it. Here’s a couple of examples.
All these examples assume the information is something that the players who don’t have access to the information want, for whatever reason. Maybe discovering it is the object of play, or discovery helps achieve other objectives.
Only One Person Knows
One example would be when a Gamemaster in a traditional roleplaying game has some secret or privileged information: the identify of a killer, a secret route through the dungeon, whatever. A non-hobby example would be the mystery object in 20 Questions. Often this information is generated by that person’s imagination, or by a procedure that only that person can see (a random table, card draw, etc.) It might be represented by an artifact, such as a card or written down on a note, or it might just exist in the person’s mind.
To get the information, you’ve got to get them to tell it to you. Maybe the agreed upon rules force them to tell it to you under a certain set of circumstances (“Is it a breadbox?”), or you have to social-fu your way into convincing them you’ve earned the right to be told the answer.
Everyone Knows But One
A rarity in roleplaying, but common in parlor games, every player but one is privy to some secret. In the Psychiatrist, one player asks each player a question in turn, who are all pretending to have some humorous delusion. The ‘patients’ confer privately on what to go upon. In Betrayal on the House on the Hill, when the Traitor is revealed, he leaves the room, allowing the Heroes to go over their objectives and plans. (Note that the Traitor’s information is an example of Only One Person Knows, above.)
What if you want nobody to know, at least to start?
The Information is On a Card
Cards are great. You can have different possibilities on a card, deal them out, put them aside, put them on a deck, whatever. Sometimes, the ‘answer’ card is set aside, and players have to divine its identity by logically proving its absence (such as in Clue, or more complicatedly in Seluth or Mystery in the Abbey)
The Card is Your Identity
Cards used again here: every player is dealt a card showing their team, or even just a hidden objective. (Mafia/Werewolf are the essential loyalty ones, or Battlestar Gallactica or Camelot for boardgames. Mountain Witch is the best example of an rpg that does this.) Generally, determining the nature of other player’s cards is a key objective in play (although not in Mountain Witch), and this is done not by deductive logic (generally), but by study of player behaviors and in-game actions. In Mafia, determining the identity of the Mafia (or hiding, if you are) is the whole game. In BSG, it certainly helps to identify the Cylons, if only to minimize the damage they can do.
Note that Mafia/Werewolf has a gamemaster, and goes through two game states very quickly: once the cards have been dealt, everyone’s identity is secret, but soon after the gamemaster learns all the identities, and the game enters a Only One Person Knows state. (The role of the gamemaster is essential for logistics reasons. The Mafia have the ability to secretly select and ‘kill’ another player.)
Cards can be shuffled into a deck and have a position relative to other cards. In the recent D&D boardgames, the location of a certain tile is key to the adventure and is shuffled into a certain portion of the deck; no one knows exactly when it will come up. A card can be given importance by putting it at the top or bottom of a deck. Players can’t gain information about what card is where without looking at/through the cards, or by drawing and removing them.
Dice have different properties than cards, most notably independence. If one card is the four of hearts, we know all the other cards (if from the same deck) aren’t. But if one die shows a four, that tells us nothing about the other dice.
If a die is rolled and put under a cup, it’s identity can be concealed. But there’s no way to tell the result, short of looking at it. Liar’s Dice gives players access to the information of different sets of dice.
The Information is the Game
This technique is largely exclusive to computer games, due to the difficulty of analog implementation. (Mao does it, but essentially requires a gamemaster figure to moderate) In this situation, the game rules themselves are obscured from the players, and determining the nature of the process is a challenge. For example, many MMORPGS have damage formulae that are quite complex, and whole communities exist to try to reverse engineer the rules so they can more accurately determine the impact of certain play choices.
You might have this in a roleplaying game if there are secret rules: players can see their inputs going in, and the outputs coming out, and have to determine how to best choose their inputs to maximize outputs. Deadlands had a number of rules secrets, the goal of which was mostly preserving a feel of mystery and dread. Use this sparingly- I imagine it’s more likely to evoke frustration rather than wonder.