Coup is a card game by Rikki Tahta of La Mame Games. Treason Coup is an open source web version of the game by Chris Brown and Jackie Niebling. It's a lot more fun to play in person than on the web, so buy the card game on Amazon if you don't already have a copy. Treason Coup runs in Node.js and is tested using BrowserStack - thanks for the free account guys!
Each player begins the game with two roles which are secret from the other players; these are your influences. Through various actions, players can be forced to reveal an influence. When both of a player's influences are revealed they are knocked out of the game. The last player with one or more unrevealed influences wins.
There are five different roles: ambassador, assassin, captain, contessa and duke. Each player's influences are drawn from a pool of 15, containing three of each of the five roles. Each player also starts with $2, drawn from an unlimited central store of money.
At the start of their turn, a player performs one of several actions. Some actions can always be played, while others require a specific role:
Since your roles are hidden, no one but you knows whether or not you have the necessary role to play the action you chose. This means that you can play any of the above actions on your turn, regardless of what roles you actually have. However, if another player suspects that you do not have the role you claim, they may challenge you. If you are challenged, you must show the role that you claimed. If you do so, the challenger must reveal one of their influences as a penalty for challenging you incorrectly. They can no longer use this influence for the remainder of the game. The role you showed is shuffled back into the deck, and you draw a new card to replace it. After such a failed challenge, your original action is completed as usual.
On the other hand, if the challenger is right and you do not have the role that you claimed, you must instead reveal one of your own influences, which you can no longer use for the remainder of the game. If successfully challenged in this way, your original action is not carried out. Note that there are three basic actions which do not require a specific role and can never be challenged: income, foreign aid and coup.
If your action is not challenged, a player may instead choose to block your action with one of their own roles, as described in the list above. If anyone suspects that the blocking player does not have the role they need in order to block the action, the blocking player can be challenged too, in the same way as above, with the same consequences.
Note that there are two ways to lose both your influences in the same turn. Firstly, by incorrectly challenging an assassination: you lose one influence for the failed challenge, and another by being assassinated. Secondly, when a player tries to assassinate you, and you falsely claim to have a contessa in order to block the assassination: if challenged, you lose one influence for the successful challenge against you, and another by being assassinated.
Coup Reformation introduces a new role, the inquisitor, who can choose one of the following actions: