Sudokuruudukko

Sudokuruudukko is a logic-based number-placement puzzle. The objective is to fill a 9x9 grid with digits so that each column, each row, and each of the nine 3x3 subgrids that compose the grid (also called "boxes", "blocks", or "regions") contains all of the digits from 1 to 9. While the solver is given a partially completed grid, the challenge lies in deducing the missing numbers by applying logical reasoning.

The puzzle is a variant of Sudoku. The name "Sudokuruudukko" is a portmanteau, combining "Sudoku" with "ruudukko," which is Finnish for "grid." This suggests a possible origin or strong association with Finland, or simply a descriptive name emphasizing its grid-based nature. Like standard Sudoku, Sudokuruudukko relies on constraint satisfaction. There is typically only one unique solution for a well-formed Sudokuruudukko puzzle.

Solving a Sudokuruudukko involves identifying cells where a digit can be uniquely placed based on the digits already present in its row, column, and 3x3 box. Common techniques include scanning for single possibilities within a row, column, or box, and eliminating possibilities based on confirmed digits in intersecting areas. More advanced strategies involve looking for pairs, triples, and other patterns of potential candidates within specific areas of the grid. The puzzle's popularity stems from its accessible rules and the satisfying mental challenge it provides.