CS Unplugged activity

Spit-Not-So: A Word Game With a Secret

About 20 minutesPairPencil

Spit-Not-So looks like a word game, but it hides a secret. The same nine words can be arranged so the game becomes almost easy to win. Finding that arrangement is what computer scientists call choosing a good data structure: organizing information so a task is simple instead of hard.

The words

SPIT
NOT
SO
FAT
FOP
AS
IF
IN
PAN

How to play

Play with a partner. Each of you picks a different mark, like a circle or a box, to claim a word.
Take turns marking one unclaimed word from the list above.
Once a word is marked, nobody else can take it.
You win by claiming three words that all share the same letter.
If every word is claimed and nobody has three words with a shared letter, it’s a draw.

A worked example

Here’s a real game, one word claimed per turn:

SPIT, SO, FAT, NOT, FOP, IF, PAN.

Player 1 claimed SPIT, FAT, FOP, and PAN, in that order. Look closely: SPIT, FOP, and PAN all contain the letter P. Three words, one shared letter, Player 1 wins.

Play a full game with your partner now, using the plain list above. Notice how much reading and rereading it takes to spot a shared letter.

Now play the secret way

The exact same nine words, arranged in a grid instead of a list, turn this into a game you already know:

NOT	IN	PAN
SO	SPIT	AS
FOP	IF	FAT

Every row, every column, and both diagonals share exactly one letter. The middle row shares “S”, the bottom row shares “F”, the right column shares “A”, and so on. Claiming three words in a straight line is exactly the same as claiming three words that share a letter, because that’s how this grid was built.

Play again with your partner. This time, mark an X or O over each word your side claims, instead of circling it, and look for lines instead of reading letters.

Check yourself. Whoever wins should have three words in a straight line on this grid (a row, a column, or a diagonal), and those three words really do share a letter, you can check by reading them. Playing the list version and the grid version back to back, the grid version should feel much faster.