I'd like to be able to substitute other items as the visual representation for

cell values. For example, there is "ColorKu" which uses 9 colors of spheres

instead of numbers. Or possibly letters instead of numbers.

Also, I'd like to be able to use other grids than the standard 9x9. For

example the LA times is publishing sudoku puzzles based on a 6x6 grid where

the subcells are 2x3. Obviously the basic concept works with any square size,

from 2x2 to infinity. Imagine "super sudoku" with 4x4 cells and 16 possible

values.