Sudoku is a logic puzzle and one of the most engaging hobbies.

Benefits
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A very good way to keep our brain in shape, in addition to being tremendously entertaining, is to solve mental puzzles like sudoku. Experts on the subject have shown that solving sudokus stimulates logic, memory, reasoning and increases the ability to concentrate, among other benefits.

Rules
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The objective is to fill in a 9 × 9 cell grid divided into 3 × 3 sub-grids with the figures from 1 to 9 starting from some numbers already arranged in some of the cells.
No number should be repeated in the same row, column or sub-grid.

You can choose different levels according to your skill, from very easy, through normal or medium, to very difficult.