*I actually adore these, but use them less than 1% of the time. Then there are the Complex Dual/Triple Forcing Chains* (some people call this SBN with Colouring). These will solve virtually all Sudokus found within the Mainstream Media (MSM). Advanced techniques: X-Wing, (Exo-) Finned X-Wing, Swordfish, SkyScraper, 2-String Kite, Empty Rectangle, etc., etc. Usual techniques: Naked Singles/Pairs, Hidden Singles/Pairs, Claiming/Pointing Pairs/Triples, etc. If it is good enough for computer programmers, why is it not good enough for Sudoku solvers?

Furthermore EVERY computer program for solving sudoku incorporates a 'guessing' module for those sticky Sudoku that cannot be resolved with their program. When you ask yourself 'could a 2 go here?' you are effectively guessing. It happens in Sudoku all the time, even without your realizing it. No matter how many 'logical deductions' you make after the fact, an arbitrary selection of an option is a guess. It doesn't matter if you call it a guess, a coin-toss, a hypothesis whether you try, pretend, assume, or imagine or whether you couch it in the logic-sounding 'if.then' conditional. Random selection of an option can occur when there are nine options or then there are only two options. Secondly, the issue of 'Guessing' is the most divisive issue in Sudoku. Notes are entirely unnecessary - even for the most difficult Sudoku. First of all, ANY solvable Sudoku can be solved without making any marks in the Matrix except to pencil in the Solution.

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