Latest Changes and Additions

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

Innies and Outies
Date Created: Sunday 13-Apr-2008
Last Updated: Tuesday 22-Apr-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.

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


Rule of 720
Date Created: Friday 28-Mar-2025
Last Updated: Tuesday 1-Apr-2025
Explains the Rule of 720 and how it is based on multiplication in the same way that the Rule of 21 is based on addition

Main Page
Date Created: Thursday 10-Apr-2008
Last Updated: Monday 17-Mar-2025
Strategies for Sudoku, Sudoku X, Killer Sudoku and Jigsaw Sudoku - and the home of logical puzzle maker Andrew Stuart

Sudoku Solver - Version History
Date Created: Sunday 13-Apr-2008
Last Updated: Thursday 13-Mar-2025


XY-Chains
Date Created: Friday 11-Apr-2008
Last Updated: Thursday 6-Mar-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.

WXYZ-Wing
Date Created: Friday 11-Apr-2008
Last Updated: Monday 10-Feb-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.

KenKen Parity Strategy
Date Created: Wednesday 1-Jan-2025
Last Updated: Saturday 1-Feb-2025
KenKen 6x6 strategy that uses ODD/EVEN parities to determine eliminations

Chute Remote Pairs
Date Created: Friday 24-Jan-2025
Last Updated: Thursday 30-Jan-2025
A simple pattern to try early on

Gurths Theorem
Date Created: Saturday 28-Sep-2019
Last Updated: Saturday 25-Jan-2025
Gurth's Symmetrical Placement Theory is discussed