From the designer website:
Twelve Twelves is a simple card game of prediction and bluff for two players. It is also a game that will fairly quickly and painlessly teach people their times-tables. The game consists of four hands and takes about 5 or 10 minutes.
Each hand works as follows:
1. deal six cards to each player
2. the dealer then chooses a card from her hand and plays it face up on the table
3. the other player (the scorer) then plays a card on top of this
4. the scorer gains points equal to the value of the two cards multiplied together
5. repeat steps 2 to 4 for the other five cards
Now play the next three hands, alternating who is the dealer and who is the scorer. There will be 4 cards left over: these are simply discarded.
The value of each card is as follows:
- Aces are worth 1
- Number cards are worth their face value
- Jacks are worth 11
- Queens are worth 12
- Kings are worth zero