Puzzle & Brain Games Fun Sudoku

Fun Sudoku uses the classic 9-by-9 grid. Fill every empty cell with digits 1 through 9 so each row, column, and 3-by-3 box contains every digit exactly once. Begin by scanning units with many given numbers and locate a naked single, a cell whose row, column, and box leave only one candidate. After direct singles are exhausted, inspect one digit across each unit. If seven, for example, has only one legal cell in a box, it is a hidden single even when that cell currently lists other candidates. Every placed digit must be removed from candidates in its row, column, and box immediately; stale notes create false contradictions later. Harder puzzles benefit from candidate pairs. When exactly two cells in one unit contain the same two candidates, those digits are locked into the pair and can be removed from other cells in that unit. Intersections between boxes and lines provide another deduction. If all candidates for a digit inside one box lie in the same row, that digit can be removed from the rest of the row outside the box. A standard puzzle rewards a logical chain rather than trial speed. When no certainty appears, change the row, column, or box being scanned. A new entry elsewhere often constrains the previously blocked region from another direction. If a duplicate digit appears or one cell loses every candidate, return to the latest entry that lacked proof while preserving earlier confirmed deductions. Difficulty changes the length of the chain, but the reliable habit remains recording what justifies each placement. The completed grid is satisfying because every entry can be explained, not because a guess happened to work.