Sudoku is a puzzle with a grid containing nine large blocks. Each block is divided into its own matrix of nine cells. The rules for solving Sudoku puzzles are very simple: each row, column and block must contain one of the numbers from "1" to "9". No number may appear more than once in any row, column, or block. When you’ve filled the entire grid, the puzzle is solved.

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A scoring system has now been introduced. The motivation behind this is to try introduce a uniform performance metric across all puzzles, including those entered manually from other sources. For details on the scoring formula, see the blog post or the Help Document. Using the Save/Load and some other Solve options will invalidate scoring for that puzzle.
Personal statistics are now also recorded for users that have registered. This includes a Rank Index which is the average of the last 12 scores discarding the highest and lowest. Your stats will be shown whenever you complete a puzzle which records a score. If you have not registered yet, join now for free.

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