Irish switch, also called two-four jacks or black jack (not to be confused with blackjack), is a popular version of the card game Switch which is played in Ireland. It is very similar to the original with a few rule changes. Switch is a shedding-type card game for two or more players that is popular in the United Kingdom, and as alternative incarnations in other regions. The sole aim of switch is to discard all of the cards in one's hand; the first player to play the final held card, and ergo have no cards left, wins the game. Switch is very similar to the games Uno and mau mau, both belonging to the larger crazy eights family of shedding games.
Switch is played with a regular, single deck of playing cards, or with two standard decks (shuffled into one) if there are a large number of players.
Each player at his turn may play any card from his/her hand that matches the suit or the rank of the card previously played; for example, if the previous card was a six of clubs, the next player may put down any six card, or any club card, from his/her hand. Should the player not have any card available to play, s/he must pick up one card.
Players are initially dealt a similar sized hand of cards (often 9 per person when 4 or less, 7 if 4+). The remainder of the deck is placed face down and serve as a "pool" or drawing stack. At the beginning of the game the topmost card from the "pool" is revealed and, so long as this card is not a trick card, play begins. (Switch may not start with a trick card, and so if the "starting card" is a trick card, cards shall continue to be selected from the pool until a non-trick card is revealed.)
The first to play (generally, the player on the dealer's left) should select from his or her hand a card that matches either, the suit or the rank of the open card (the card that is "top"); for example, on a 10 of spades, only a spade card or a 10 may be played. If a player is not able to place a card, he draws cards from the stack until he is able to play a card.
If the drawing stack is run down and becomes empty, the playing stack or discard pile (except for the topmost card) is shuffled, and placed face down to become the new "pool."
In switch, some cards are known as "power" or "trick" cards, because their being played directly affects the gameplay: