**New.**Allows the user to select from 15 predefined puzzles of increasing difficulty and in standalone (DOS) mode toa saved game or to*Open*the current game (i.e., the sudoku puzzle and the moves done so far).*Save***Edit.**Opens up a sudoku editor. It allows the user to redefine cells in the grid. Use thebutton to clear all cells or press '0', SPACE, DELETE or BACKSPACE to clear a single cell. All other non-digit values are discarded. Move around with the*Clear*or just*arrows*in a cell to edit. Use the editor to import puzzles from popular generators or from books, journals etc. or to define and test your own puzzle.*click***Solve.**Allows the user tothrough the solution manually (*Step*,*one*or*five*steps at a time) or launch automatic*ten*of the solution. It also allows to*Run*the current state of the solution or to*Check*all the solutions, in case more than one are found.*Show***Manual play.**Allows the user to play manually the puzzle. Click in a puzzle cell or move around with the arrows from cell to cell. When in a cell, either type the possible numbers for the cell or click on the corresponding positions on the right-hand 3x3 area. Typing an existing number or clicking on an existing number removes this number from the possibilities for the selected cell. Control-click on the right-hand 3x3 area to clear all the numbers for this cell. If you wish, you can choose one number to highlight in single-numbered cells within the puzzle. Before moving in a different cell, you can type a comment in the text area below the puzzle. This will be automatically saved when you save the puzzle and can be retrieved during play-back (however, retrieval is not allowed for regular users).**Reset.**Allows the user to restart the puzzle.

,*Shift-"+"*,*shift-control-"+"*: Step through the solution*shift-alt-"+"**one*,*five*or*ten*steps at a time, correspondingly.,*Shift-"arrow"*,*shift-control-"arrow"*: Step through a recorded game*shift-alt-"arrow"**one*,*five*or*ten*steps at a time, correspondingly. The "arrow" can be any one of the four keyboard arrow keys (up, down, left or right). This feature is available only in standalone (DOS) mode.**Caution!**While the automatic solution uses "batch" steps that span the whole puzzle for several patterns, the play-back of a recorded game steps one cell at a time. Thus many changes in internal cell possibilities will not be directly visible, unless a manual player is invoked, which shows all the cell possibilities. This feature serves to discourage cheating by the user: if a cell is manually edited in the player then the play-back cannot proceed anymore.,*Alt-'o'*: Open a saved game or save the current one. Loaded games can be stepped through and continued manually or automatically.*alt-'s'*

- This is a
**cognitive modeling**study. It uses only four solving rules of increasing complexity that recognize simple situations or patterns of numbers. For arbitrary Sudoku-like puzzles that have multiple solutions or none, an additional trial-and-error rule is used that allows to select options and backtrack, if necessary. For a well-formed Sudoku that has a unique solution, there is no need to use trial-and-error of any kind. In the case of multiple solutions, the solver will produce the first three solutions reached (they can be inspected with the option "Show solutions" from the popup menu). Finally, in the case of impossible puzzles the solver will report there is no solution after a while of backtracking.__More details will appear after a trial period is over__. - Creating the puzzle is more complicated than solving it. Even when a puzzle is
correctly created, the rating of its difficulty may be largely arbitrary. From a
cognitive point of view, the solver gives its rating for the puzzle in terms of
the rules it used to solve it (
for regular Sudoku's with a single solution,*"1-4"*or*"abnormal"*for multiple or no solution cases).*"erroneous"*__More details will appear after the trial period is over__.

- Frazer Jarvis' Sudoku pages
(
__http://www.shef.ac.uk/~pm1afj/sudoku/__) - My favorite Sudoku puzzle generator
(
__http://www.websudoku.com__) - Another Sudoku puzzle generator
(
__http://www.sudoku.com__) - Another Sudoku puzzle solver
(
__http://www.sudokusolver.co.uk__)