Sudoku in HTML5

1. No number can repeat itself in the same 3x3 square
2. No number can repeat itself on the same 9 cells column or row.
3. Every empty cell should have a "mirror" empty cell (for example cells [0,7] & [8,1] or [3,3] & [5,5]). Also when cells and 3x3 Cox index starts from "0", left to right, top to bottom.
4. Each game should have one and only one solution to be considered a valid Sudoku game.

• New: The user can select among multiple difficulty levels:

• Save/Restore: The user can save the game.

• Undo: Undoes the last digit entered or other user actions such as Accept or Solve. It is implemented using a stack so records can undo an unlimited number of actions. A Load, Reset or Clear empties the undo stack.
• Hint: Enters the answer to the current cell in that cell. It gets the answer from the current board hence if the board is already incorrect, no hint will be given.
• Restart: Play the same game from a state before any move was first made.
• Solve: Solves the entire problem from the current position. This may not give the solution if values already entered are incorrect.

• On: The user can hear the sound while solving the Sudoku.
• Off: The user solves the Sudoku in silent mode.

• On: The user can solve the Sudoku using the keyboard.
• Off: The user solves the Sudoku without any use of the keyboard.

• Rules:

1. No number can repeat itself in the same 3x3 square.
2. No number can repeat itself on the same 9 cells column or row.
3. Every empty cell should have a "mirror" empty cell (for example cells [0,7] & [8,1] or [3,3] & [5,5]) Also when cells and 3x3 Cox index starts from "0", left to right, top to bottom.
4. Each game should have one and only solution to be considered a valid Sudoku game.

• About: The puzzle was introduced in Japan by Nikoli in the paper Monthly Nikolist in April 1984 as "Sūji wa dokushin ni kagiru", which can be translated as "the digits must be single" or "the digits are limited to one occurrence". (In Japanese, dokushin means an "unmarried person".) At a later date, the name was abbreviated to Sudoku by Maki Kaji, taking only the first Kanji of compound words to form a shorter version. Sudoku is a registered trademark in Japan and the puzzle is generally referred to as Number Place. In 1986, Nikoli introduced two innovations: the number of givens was restricted to no more than 32, and puzzles became "symmetrical".