Sum 15

And now for something completely different.

I wanted an activity for my spare class periods at the end of this week, so I wrote up rules for a card game.  I wanted to use familiar card game concepts, but also put a slight mathematical challenge in, to make it a little more than just a time-waster.  It also had to be something that I could scale to different class sizes.

Cribbage immediately came to mind, an in fact my first run was essentially just the play from cribbage expanded for more players.  This was challenging, especially as I tried to run it with the whole class in one game using multiple decks.

The second run I split the class into smaller groups, and also tried awarding points to multiple players for each play, which one of my three groups got the hang of but proved unrealistic.

The third run I kept the class split up, and reworked the ruleset to essentially what’s below, which looks more like a rummy variant.  15s were changed to 14s, and the limit of 31 changed to a reset on multiples of 15.  I hadn’t worked out a clean method of scoring for this class.

The fourth class I ran again split up, and the last class I ran a game with the whole class and multiple decks.  The fourth and fifth runs came out relatively smoothly, though I wouldn’t call the reception enthusiastic.

“Sum 15” is a working title and referred in the end to the reset rule for multiples of 15.  I haven’t come up with anything better yet.

PLAY
Deal 6 cards to every player
Place the remaining deck in the middle and turn a starter card face up
Each player going around left of the dealer must play a card in turn until all cards dealt have been played
Cards played remain face-up in the middle unless a set is made

SETS
A player who plays a card to make a set picks up those cards and places them face down in front of them.
A set is made if:

• The last two cards played sum to 14; for sums, Ace is 1, Jack 11, Queen 12, King 13
• The last two cards make a pair
• The last three cards are in order, for instance 2-3-4 or Q-J-10

SUM FIFTEEN
If a player can play a card so that the total value of all cards in the middle is a multiple of fifteen (15, 30, 45, 60, etc.), then that player picks up ALL the cards in the middle.
Then place a new starter from the remaining deck face up and continue in turn beginning with the next player.

WINNING THE GAME
When all players have played their six cards, the player with the most cards picked up wins

There’s a limit on how many players you can play with off a single deck.  I think a maximum of six players per deck is the correct rule of thumb, but I ran a game with 14 players with only two decks.  How much of this was my students missing point plays (and so needing fewer restarts) I’m not sure.