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In my experience, it's generally What is the hardest technique required to solve it.

  • Example hardest: Single Position - Easy puzzle
  • Ex. Candidate Line - Medium Puzzle
  • Ex. Naked Pair - Hard Puzzle
  • Ex. Swordfish - Very Hard Puzzle
  • Ex. Forcing Chains - Master Puzzle

Definitions can be found here: http://www.sudokuoftheday.com/pages/techniques-overview.php

In my experience, it's generally What is the hardest technique required to solve it.

  • Example hardest: Single Position - Easy puzzle
  • Ex. Candidate Line - Medium Puzzle
  • Ex. Naked Pair - Hard Puzzle
  • Ex. Swordfish - Very Hard Puzzle
  • Ex. Forcing Chains - Master Puzzle

In my experience, it's generally What is the hardest technique required to solve it.

  • Example hardest: Single Position - Easy puzzle
  • Ex. Candidate Line - Medium Puzzle
  • Ex. Naked Pair - Hard Puzzle
  • Ex. Swordfish - Very Hard Puzzle
  • Ex. Forcing Chains - Master Puzzle

Definitions can be found here: http://www.sudokuoftheday.com/pages/techniques-overview.php

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source | link

In my experience, it's generally What is the hardest technique required to solve it.

  • Example hardest: Single Position - Easy puzzle
  • Ex. Candidate Line - Medium Puzzle
  • Ex. Naked Pair - Hard Puzzle
  • Ex. Swordfish - Very Hard Puzzle
  • Ex. Forcing Chains - Master Puzzle