Sudoku - is a logic-based, number-placement puzzle. The modern Sudoku was most likely designed
anonymously by Howard Garns, a 74-year-old retired architect and freelance puzzle constructor from Indiana,
and first published in 1979 by Dell Magazines as Number Place (the earliest known examples of modern Sudoku).
The puzzle was popularized in 1986 by the Japanese puzzle company Nikoli, under the name Sudoku,
meaning single number. It became an international hit in 2005. (from Wikipedia,
http://en.wikipedia.org/wiki/Sudoku)
The objective is to fill a 9×9 grid with digits so that each column, each row,
and each of the nine 3×3 sub-grids that compose the grid (also called "boxes", "blocks", "regions",
or "sub-squares") contains all of the digits from 1 to 9.
The same single integer may not appear twice (a) in the same 9x9 playing board row,
(b) in the same 9x9 playing board column or (c) in any of the nine 3x3 subregions of the 9x9 playing board.
Author Dmitry Y. Kazarov
write an E-mail.
How to play: Playing board consists of cells. Some cells contains the unchangeable black
digits. Other cells contains light grey numbers from 1 to 9. These are options for this cell.
Single click on an option hightlights it with black color. It helps to memorize probable
digit for this cell.
Double click on an option to make it a solution for this cell (blue colored digit).
Double click on a cell with solution removes solution and restores list of options.
Under playing board:
Checkbox Highlight possible cells controls highlighting of cells which can contain digits pointed
by mouse cursor (cell values or options) without conflicting with other cell values.
Selectors Difficulty and Symmetry sets these parameters for new game.
Button New game loads new puzzle (all saved states becomes unavailable).
Button Clear removes all changes to puzzle restoring initial state of the game.
Button Mark all options highlights all options not conflicting with the cell's values
Button Clear all options removes highlightings from all options.
Using buttons Save and Restore you can store and recall state of playing board for current
game. The reloading of the game removes all saved states. Text field above buttons allows to give a name to
state.