Latest Changes and Additions

A quick list of the latest updates and additions to this site:

Grading Puzzles
Date Created: Tuesday 30-Sep-2025
Last Updated: Monday 6-Oct-2025


BUG
Date Created: Friday 11-Apr-2008
Last Updated: Sunday 28-Sep-2025
Sudoku Strategy. BUG stands for Bi-Value Universal Grave. It is a formation that relies on the uniqueness of the solution and an array of bi-value cells.

Sudoku Min-Lex
Date Created: Monday 22-Sep-2025
Last Updated: Monday 22-Sep-2025

Tridagons
Date Created: Friday 19-Sep-2025
Last Updated: Saturday 20-Sep-2025
The Tridagon or Thor's Hammer is a Sudoku strategy discovered by Denis Berthier

Various Static Patterns
Date Created: Wednesday 14-May-2025
Last Updated: Friday 19-Sep-2025


What's New
Date Created: Monday 17-Aug-2009
Last Updated: Friday 19-Sep-2025


XY-Chains
Date Created: Friday 11-Apr-2008
Last Updated: Friday 12-Sep-2025
Sudoku Strategy. XY-Chains are the work-horse of chaining strategies and are very easy to use when the board contains many bi-value cells. When the start and end cells can see a common candidate eliminations can be made.

Hidden Unique Rectangles
Date Created: Wednesday 23-Apr-2008
Last Updated: Thursday 4-Sep-2025
Sudoku Strategy. Hidden Unique Rectangles extends Unique Rectangles that take advantage of the fact that published Sudokus have only one solution. Formations and strategies based on this notion and are explained here.

Almost Locked Sets
Date Created: Saturday 12-Apr-2008
Last Updated: Monday 1-Sep-2025
Sudoku Strategy. Almost Locked Sets are complex building blocks that all allow one to continue a chain. They are groups of cells of size N with N+1 candidates in them.

KenKen Combinations
Date Created: Friday 3-Jul-2009
Last Updated: Monday 1-Sep-2025