The rules as given here are a simplified version. In most regular variants of the game, there are 11 categories (for a total of 44 cards) rather than the three used here, and there can be more than 3 players. Where these choices have an effect on the knowledge changes, this will be noted.
A set of 12 cards is divided randomly among three players, without allowing the players to see which cards the others get. Among these cards there are 3 unique cards, each of which is the first of a different category. The other 9 cards are blanks, which will become cards of these three categories as the game progresses. Each of the blanks will become card 2, 3 or 4 for one of the categories, and there can be only one of each card/category combination. Each of the players knows what the three categories are.
A randomly selected player gets the first turn. He must ask one of the other players for a particular card from a category he also has a card from. If that player has the card asked for, he will hand it to the player whose turn it is. If there is no way in which he could not have the card based on the common knowledge from the rules and previous cards asked, one of the asked player's blanks will be turned into the card asked for, and it will be given to the asking player. In both of these cases, the asking player keeps the turn, and he must ask for another card from one of his opponents. If the asked player does not have the card, or there is a situation consistent with his knowledge and the rules where he would not have the asked card, no card is given and the asked player gets the turn.
If a player owns all four cards of a category, he must reveal this to the other players. From this point onwards, players can no longer ask for these cards. The game ends when all categories have been completed and revealed. The player with the most completed categories wins.