Latest Changes and Additions

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

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


Innies and Outies
Date Created: Sunday 13-Apr-2008
Last Updated: Thursday 28-Aug-2025
Killer Sudoku Strategy. An essential strategy for Killer Sudoku. It looks at the cells in cages which all inside or outside a unit or group of units. Since a unit must add up to 45 (in 9x9 Killer) overlaps can help remove candidates.

Finned Swordfish
Date Created: Saturday 12-Apr-2008
Last Updated: Wednesday 27-Aug-2025
Sudoku Strategy. Finned Sword-Fish extends the Sword-Fish strategy but it has extra candidates of X that prevent one of the three trios normally required. Eliminations are still possible in this fin.

What's New
Date Created: Monday 17-Aug-2009
Last Updated: Friday 22-Aug-2025


WXYZ-Wing
Date Created: Friday 11-Apr-2008
Last Updated: Sunday 17-Aug-2025
Sudoku Strategy. WXYZ-Wings extend XYZ-Wings to four numbers and are four cell formations used to eliminate candidate elsewhere. They use a common candidate method to find contradictions.

3D Medusa
Date Created: Saturday 6-Mar-2010
Last Updated: Thursday 14-Aug-2025
Sudoku Strategy. 3D Medusa takes chain building into all the dimensions of the Sudoku board. That is, by making links among rows, columns and boxes - and in bi-value cells. Many types of eliminations are possible with this network approach.

Donations
Date Created: Saturday 12-Apr-2008
Last Updated: Saturday 26-Jul-2025