The rules: insert the digits 1-6 just once in each a) row, b) column, c) bold outlined area AND d) in each white and gray rectangle. Peter Ritmeester is the inventor of the Hyper Sudoku , where four gray regions also contain 1-9. By applying this idea to a 6x6 sudoku, an entirely new dimension of logic is created, making a Sixy perhaps even more fun than a 9x9 sudoku. Not time consuming hard work, but plenty of logic and insight. Errors are unlikely, with twice as many puzzles (and a six page How-To) in the same amount of space! Ritmeester, owner of PZZL.com, created the puzzles for all sudoku books presented by Will Shortz, with average reviews of 4.5 stars .
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