The next big step in the origin of [M] games was Sudoku.
Believed to have been created by Howard Garns, a retired architect and freelance puzzle designer, and first appeared in 1979 in Dell Magazines as a puzzle called “Number Place”.
Sudoku didn’t become a international phenomena until 25 years later, when it began to appear in newspapers worldwide.
Garns’ great innovation was adding an additional regional constraint to the basic orthogonal constraints of the Latin square.
This innovation can in some sense be understood as adding another, regional dimension to the construct.
Although the addition of the regional constraint greatly reduced the number of possible solutions, ~1.2×10−6 times the number of 9×9 Latin squares, the number of possible unique 9×9 Sudoku puzzles is a staggering 3.10 × 1037.
From the standpoint of human perception, this an effectively infinite number of variations, far beyond the capacity of the human mind to hold, and vastly greater than the number of hours in all of our days.