Secret Code Cipher Game

Paper and pencils

A ruler for drawing neat letter grids

Colored pens or markers for cipher keys

Envelopes for sealed secret messages (optional)

Index cards for portable cipher key cards

Start with a Caesar cipher: write the alphabet in a row, then write it again shifted by 3 letters underneath (A=D, B=E, C=F, and so on).

Encode a short secret message letter by letter using the shifted alphabet.

Pass the encoded message to a partner with only the shift number as a clue. Let them decode it.

Next, try a substitution cipher: randomly assign each letter to a different letter, making a completely scrambled alphabet.

Encode a message with the substitution cipher and pass it along with no key at all.

Discuss letter frequency — E, T, A, and O are the most common letters in English. Look for the most repeated symbol in the coded message and guess it might be E.

Try a number cipher: A=1, B=2, and so on. Write messages as number strings separated by dashes.

For an advanced challenge, layer two ciphers: shift letters first, then convert to numbers.

Seal a final cipher message in an envelope and challenge a family member to crack it by dinnertime.

Make a personal cipher key card on an index card to keep and reuse.

Start simple. The Caesar cipher with a shift of 3 is the perfect on-ramp. Once kids feel the decoding thrill, they'll want harder challenges.

Have kids write the full alphabet grid every time rather than working in their head. It prevents errors and builds systematic thinking.

If stuck on a substitution cipher, look for single-letter words ('I' or 'a') first. These anchor points unlock the rest.

Connect it to history: Caesar used this for military messages. Kids love using a 2,000-year-old spy technique.

Make it ongoing — leave coded messages on the fridge or in lunchboxes throughout the week.