deduction

Description from the publisher:

The city of London has been shaken by heinous crimes, and Scotland Yard is groping in the dark. 13 Clues, set at the end of the 19th century, puts players in the shoes of the detectives, each trying to solve their own mystery. Each player sees the clues — person + location + weapon — for the other players but not their own. They investigate by asking questions, by consulting the secret informant, and by making accusations in order to collect clues and rule out suspects. The goal of the game is to identify which of the 13 clues match their case before the others do!

CrossTalk is the party game of subtle conversation in which two teams race to guess secret keywords. Each round, teams select a clue-giver, and those clue-givers are given knowledge of the same secret keyword. The goal of the clue-givers is to help their teammates guess this keyword before the other team.

The round begins with both clue-givers writing a one-word clue to give their team in private. Then, clue-givers will alternate providing one-word public clues to everyone — but there is a catch! After your team gives a public clue, the other team — and only the other team — may attempt to guess the keyword. Clue-givers will need to use their private clue to provide context for the future. This will allow them to slip public clues by the other team.

The round ends when one team correctly guesses the keyword or both teams run out of guesses. Each correct guess is worth 1 point, and the first team to earn 5 points wins.

Zendo is a game of inductive logic in which one player, the Master, creates a rule that the rest of the players, as Students, try to figure out by building and studying configurations of the game pieces. The first student to correctly guess the rule wins.

Inspired by Eleusis, Zendo uses Looney Pyramids but was released as a standalone game in July 2003. In 2017, a version of Zendo was released that had only one size of pyramid but added blocks and wedges. It also includes an optional system of cards for generating the Master's rule, useful for novice players who are not yet comfortable making their own rules.

In Sleuth, a classic deduction game from master designer Sid Sackson originally released as part of the 3M Gamette Series, players are searching for a hidden gem, one of 36 gem cards hidden before the start of the game. The remainder of this gem deck – with each card showing 1-3 diamonds, pearls or opals in one of four colors – is distributed evenly among the players, with any remaining cards laid face up. Thus, you and everyone else starts with some information about what's not missing.

A second deck contains 54 search cards, each showing one or two elements, such as diamonds, pairs, blue opals, red pearls, or an element of your choice. Each player receives four face-up search cards; on a turn, you choose one of those cards and ask an opponent how many gem cards they have of the type shown. If you ask for, say, pairs, the player must tell you how many pairs they hold but not which specific pairs; if you ask for something more specific, say, red diamonds, the player reveals to everyone how many such cards she holds while you get to look at them in secret.

Players track information on a score pad. You can guess the hidden gem at any time, or on your turn you can ask any one question regardless of which search cards you have, then immediately make a guess by marking your sheet and checking the hidden gem card. If you're wrong, you keep playing but can only answer questions; if you're correct, you win.

The simplicity of the rules and the cards belies the complexity of the game. In some cases you see cards, while in others you hear only the number of cards that an opponent holds, making it tough to deduce. Any notation system you devise must be both flexible and reliable, recording negative information as well as positive in order to tick off the possibilities one by one...

Reimplements:

The Case of the Elusive Assassin, with the core mechanisms of that game being used in Sleuth, minus the game board, movement and player proximity.

Description from the publisher:

Destination X is a different kind of game experience: One player takes the moderator role as a spy on the run, while the remaining players are detectives who must cooperate and use their deductive skills and geographical knowledge to track down the spy and identify their secret destination.

At the beginning of each round, six destination cards are placed face up on the table. The spy secretly chooses one of the destinations, and flips to the chosen country's page in the handbook. Each detective is given three informant cards, and in turn each detective must play an informant to get information about the spy's secret destination. The spy must find the relevant information in the handbook and answer truthfully. The informants may provide information on various aspects such as population, industry, religion, history, economy, and so on. After a detective has played an informant, the detective must also eliminate one of the destinations on the table.

At any time, the detectives can decide to guess on the spy's destination. If they guess correctly, the detectives win the round; otherwise the spy wins. The spy also wins if the detectives run out of informant cards, so the detectives must manage their resources well and not spend too much time or else the spy will manage to get away. The first side to win three rounds wins the game.

No prior geographic knowledge is needed to play. Since Destination X is a team-based game, it can be played in groups of any number of players.