Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9.

Click on any cell in the grid to place the cursor selector on it. Click in list of digits to the right of the grid to assign a digit to a cell. Click on the blank item in that list to clear the assignment for the selected cell.

Double-clicking within the selected cell will assign the digit corresponding to the region of the cell that was clicked.

If Show Bookkeeping is checked, then clicking within the selected cell will toggle the bookkeeping for the digit clicked.

Note that the digits initially revealed cannot be changed.

• Arrows move the cursor up, down, left, or right.
• ctrl-arrow move the cursor up, down, left, or right, skipping any assigned cells.
• space clears the assignment under the cursor.
• a digit (0-9) assigns it to the cell under the cursor.
• shift + digit toggles the bookkeeping in the cell for that digit. This only works if Show Bookkeeping is checked.
• ctrl-z will undo a change to the puzzles. Multiple changes may be undone.
• ctrl-y will redo an undone change. Multiple changes may be redone.

Note that the digits initially revealed cannot be changed.

Note that after clicking one of the buttons below the puzzle (Save, Clear, Highlight, Hint, or Cipher on Top/Bottom), you may need to click on a the grid before using the keyboard controls.

• Highlight Errors causes cells with the wrong digit assigned, or the correct digit turned off in bookkeeping, to be displayed in red with an extra border.
• Show Bookkeeping shows nine digits in each unassigned cell. These can be used for bookkeeping--when a digit is determined to not be possible in a cell, toggle that digit in the cell.
• Update Bookkeeping, enabled only if Show Bookkeeping is checked, takes each assigned digit and removes that digit as a possibility in every other cell in the same row, column, and box.
• Hint changes the current cell to its correct value.
• Undo will undo a change to the puzzles. Multiple changes may be undone.
• Redo will redo an undone change. Multiple changes may be redone.
• Lock/unlock controls whether the current cell is locked. Only filled in cells may be locked. The text inside locked cells appears in gray.
• Clear resets the board.
• Save records your progress. When you revisit this puzzle, your progress will be automatically loaded. Visit the help for more information.

• http://www.sadmansoftware.com/sudoku/techniques.htm
• http://www.angusj.com/sudoku/hints.php