To be fair, some of the harder "straight" sudoku puzzles have a point where they become more chess-like -- you have to think two or three or four moves ahead because there's no place that you can definitely put a given number.
When you're into puzzles like the atrocious ones here (http://www.divingforbananas.com/sudoku/) that require techniques with names like X-Wing or Swordfish, it's probably best to just pull back.
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