The back and/or front of this shirt is a grid allowing the entry of a machine-washable sudoku. (Look up the puzzle and write in those numbers before you don the shirt.) Worn on the shirt on a string is a marker of the same, allowing and inviting people to fill it in.
-- Voice, Jun 20 2022

Innovative use of personal space; this will require an elaborate system of formal etiquette. [+]

OTOH, because of how Japanese syllabaries are pronounced, this could end up sounding a bit like "stalk me".
-- pertinax, Jun 21 2022


[approved +] You could also get it tattooed on your shaved head and carry around a range of coloured felt tip pens to write in the missing numbers, then once complete, get the numbers permanently tattooed in the colours people have used to fill in the answers.
-- xenzag, Jun 21 2022


+ Oh yes but OK I never learned to play that!
-- xandram, Jun 21 2022



random, halfbakery