What the ???
The image to the right shows 3 different ways of displaying the same Sudoku puzzle. On the right is the standard version using the numbers 1..9. In the other two puzzles there is a simple equivalent between every number in the standard puzzle and a color or letter. For example, every 2 on the right is represented by a B in the middle and a blue square on the left. One could obviously make up many other equivalent representations using other colors, letters, symbols, etc.
Why these variations?
A funny thing about Sudoku, the logic to solve each of the three puzzles above is identical, but different people will find different versions easier. It all depends on how your brain processes different kinds of information. So if your older brother is driving you mad with his skill at standard Sudoku, print one out in color, take a set of markers each, and see who's fastest now...
What are the Sudoku Rules?
A standard Sudoku puzzle has a single solution where every little square is filled with a color, number letter (etc.) - hereafter called "piece" such that:
The DC Sudoku puzzles tagged as Expert require much higher level logic than this to solve completely. Here are some sites that discuss more advanced Sudoku logic: