Game Rules

 
The object of the game is to identify a 'Set' of three cards from 12 cards
laid out on the table. Each card has a variation of the following four features:

(A) Color:
Each card is red, green, or purple.

(B) Symbol:
Each card contains ovals, squiggles, or diamonds.

(C) Number:
Each card has one, two, or three symbols.

(D) Shading: Each card is solid, open, or striped.

A 'Set' consists of three cards in which each feature is EITHER the same on each card OR is different on each card. That is to say, any feature in the 'Set' of three cards is either common to all three cards or is different on each card.
 
For example, the following are 'Sets':

All three cards are red; all are ovals; all have two symbols;
and all have different shadings.

 
All have different colors; all have different symbols;
all have different numbers of symbols; and all have the same shading.

 
All have different colors; all have different symbols; all have different numbers of symbols, and all have different shadings.
 
The following are not 'Sets': 

All have different colors; all are diamonds; all have one symbol; however, two are open and one is not.

 
All are squiggles; all have different shadings; all have two symbols; however, two are red and one is not.
 
The Magic Rule
If two are... and one is not, then it is not a 'Set'.

Quick Start
For a quick introduction for anyone playing the card version, and especially for children under six, start with the small deck (just the red cards). This eliminates one feature, color. Play as indicated below but only lay out nine cards. When you can quickly see a 'Set' with this 27 card mini version, shuffle the two decks together. You can try the quick start in this link. Here we eliminate the feature of shading, and test your skill in finding 4 'Sets' from a layout of 9.
 
The Play
The dealer shuffles the cards and lays twelve cards (in a rectangle) face up on the table so that they can be seen by all players. The players remove a 'Set' of three cards as they are seen. Each 'Set' is checked by the other players. If correct, the 'Set' is kept by the player and the dealer replaces the three cards with three from the deck. Players do not take turns but pick up 'Sets' as soon as they see them. A player must call 'Set' before picking up the cards. After a player has called 'Set', no other player can pick up cards until the first player is finished. If a player calls 'Set' and does not have one, the player loses one point. The three cards are returned to the table.

If all players agree that there is no 'Set' in the twelve cards showing, three more cards (making a total of fifteen) are laid face up. These cards are not replaced when the next 'Set' is picked up, reducing the number to twelve again. If solitaire is being played, the player loses at this point.

The play continues until the deck is depleted. At the end of the play there may be six or nine cards which do not form a 'Set'.

The number of 'Sets' held by each player are then counted, one point is given for each and added to their score. The deal then passes to the person on the dealer's left and the play resumes with the deck being reshuffled.

When all players have dealt, the game ends; the highest score wins.