But there are puzzles which allow for more complicated ideas, and some of the techniques that have grown up around sudoku have names that hint at their exotic or powerful natures: naked singles, X-wings and Y-wings, swordfish, jellyfish and even “ Phistomefel rings“. Not all sudoku puzzles are wonderful – many which are graded ‘easy’ are exercises in elimination that a mathematician would call ‘trivial’.
Occasionally they yield extraordinary patterns of logic.
The absolute beauty of sudoku is that the rules of the classic form are so simple (the numbers 1 to 9 appear in each row, column and 3 by 3 box), and yet the puzzles can be absorbing, intricate and even sometimes amazing for the solver.