1
Stage 1 of 2
su + doku
Japanese · 1980s
"the digits must remain single"
combining "su" (number) and "doku" (single), short for "suji wa dokushin ni kagiru" (the digits must be single)
2
Stage 2 of 2
sudoku
English · 2000s
"a number-placement logic puzzle"
adopted as the number puzzle became a worldwide craze
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