Techniques
The deductions that solve a puzzle — naked single, hidden single, X-wing, the killer-Sudoku 45 rule, and the rest. The solver replay deep-links into these entries when it walks through a step.
54 entries
Browse all →Glossary
Short reference entries for the techniques, rules, and terminology of Sudoku. The long-form companion pieces live in Learn.
Categories
Rules & terminology
The vocabulary of the grid — candidate, pencil mark, given, cage, unit. The structural pieces every technique builds on top of.
12 entries
Browse all →Difficulty
Beginner
Start here. The foundational techniques and terminology you'll meet on every Sudoku and Killer Sudoku puzzle — singles, pencil marks, units, cages, the basic vocabulary of the grid.
25 entries
Browse all →Intermediate
Where easy puzzles end and the harder ones begin. X-wing, Y-wing, swordfish, and the structural concepts that chain reasoning depends on — strong links, weak links, bilocation.
14 entries
Browse all →Advanced
Chains, fish, almost-locked sets, uniqueness, killer-cage arithmetic. The full toolkit for the hardest puzzles, plus the controversial trial-based moves at the edge of pure deduction.
27 entries
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