Invent a secret family code: symbols, knocks and emojis

Writing something another person cannot read is one of the oldest thrills of childhood, and nothing about it has changed. What has changed is how long the start takes: inventing twenty six distinct symbols by hand, one per letter, defeats anybody by the letter M. AI does that grinding part in a minute, and the game starts the same afternoon.

Three codes work particularly well at home. The symbol alphabet, for written notes and messages hidden under a pillow. The knocks, two short and one long, for the bedroom door. And the emoji code for the family phone, which is genuinely useful: one emoji for I have arrived, one for please come and get me, one for today went well.

The symbol alphabet

I am [AGE] years old and I want to invent a secret script for my family. Suggest a symbol for every letter of the alphabet, in the style of [runes / geometric shapes / animals / dots and dashes]. Rules: every symbol can be drawn in one or very few strokes, no symbol looks like another, and none of them is a normal letter. Give me a list of letter plus a description of the symbol, so I can draw them by hand onto my key. Add three extra symbols for space, full stop and question mark.

• The key gets drawn by hand on paper, twice: one for the child, one hidden somewhere in the house. No key, no code, and keys disappear.
• If two symbols look alike, swap one immediately. A script you cannot read stops being used within two days.
• The first message gets written the same day, even if it is four words long. What never gets used does not exist.
• A good place for the premiere: a note in the lunch box, read by somebody who also holds the key.

This is my secret script: [paste your list of letters and symbols here]. Invent five short practice messages for me, three to five words each, about things at home. Write them first in normal letters and then in my symbols. Put the solutions at the very end, separately, so I can check for myself whether I read them correctly.

That second prompt comes with a warning worth having in advance: chat models tangle themselves up when swapping letters one by one and produce the wrong symbols with total confidence. That is not an annoyance, it is the best part of the game. The child checks the message against the key in their hand, finds the mistake and corrects the machine. A child who can correct an AI has understood something important about it.