Snap Back takes 3 or more players and lasts about 10 minutes.
A deck (or more than one deck) of cards, with only the cards 2-10 (so 36 cards per deck), well shuffled.
A die per player.
Pick a dealer to be responsible for shuffling the cards and for revealing them during play.
Put one die in front of each of the other players, with the "3" face showing upwards.
The dealer picks up the deck of cards in their hands and reveals the first 6 cards, one at a time, showing it, saying the number (not the suit), then placing it face down in an ordered stack on the table.
Order of play
1. The dealer carries on dealing cards (as above), one at a time, at a constant pace (about 1 card every 2-3 seconds)
2. When a player thinks that the card just placed on the stack has a valid match, they say "Snap".
3. All players hold out a fist. The dealer counts down "3, 2, 1, reveal". On "reveal" each player simultaneously sticks out a number of fingers between 0 and 6 inclusive (6 is indicated by a thumb's up sign, 0 by a closed fist).
4. The dealer reveals the top card on the stack and the 6 before it. Players adjust the number on their die, according to the result.
5. The dealer reprises the last 6 cards and then play resumes at stage 1.
22 - a snap 1-Back - hold out 1 finger 232 - a snap 2-Back - hold out 2 fingers 2342 - a snap 3-Back - hold out 3 fingers 23452 - a snap 4-Back - hold out 4 fingers 234562 - a snap 5-Back - hold out all 5 fingers 2345672 - a snap 6-Back - hold up your thumb 8345672 - no match - hold out a closed fist 7252842 - both snap 3-Back and snap 5-Back are valid
Results of a call
Rules to determine what happens, in order of high to low precedence:
A die can't be moved lower than "1"
If you called "Snap" and you got it wrong, your die is decreased by 1. (eg 5-->4)
If you revealed a number of fingers that don't match the snap back, but there was no valid match equal or lower than your die, your die remains unchanged.
If you revealed a number of fingers that don't match the snap back, and there was a valid match equal or lower than your die, your die is decreased by 1.
If you claimed a valid match, but the match you claimed was lower than your die, your die remains unchanged.
If you claimed a valid match, and the match you claimed was equal or higher than your die, your die is increased by 1.
End of the Game
The game ends when someone whose die is showing "6" manages to correctly claim a 6-Back.
However, the actual aim of the game is to increase your intelligence by improving your working memory. Therefore, your ambition is not so much to be the one to end the game, as it is to do better than your previous best, ending on a higher score or finishing the game earlier. Since there is no player versus player strategy in this game, it can quite happily be stopped after 10 minutes (about the maximum period most people can strongly concentrate) even if the end condition has not been met. The game is more effective at boosting working memory if played often for short periods, rather than for longer periods but less frequently.
It should be noted that while there is no player versus player strategy, there are player versus player tactics involved in calling on matches lower than your die. For young children, you might want to start at "1" or "2" showing on their dice, rather than "3". If done as a school class starter activity, it can also be combined with a discussion of the mental approaches used by different players.