DKM Sudoku 16 Online Help

How To Play

  • Click the "Menu" button, then select the "New Puzzle" menu item and select a difficulty level from the dropdown menu.
  • Fill in blanks with the Pen (select a cell, then click on the number you want to enter).
  • If you're not 100% sure of a number, you can make a note of it in the cell using the Pencil. To do this, click the "Pencil" icon to be placed in "Pencil mode".
  • You may enter as many pencil marks as you like in each cell.
  • To change back to "Pen" mode, click the "Pen" icon. You can also switch between pen and pencil modes quickly by pressing the "P" key or by using the mouse wheel. (See tips below.)

Input Tips


If you prefer to use the keyboard rather than the mouse, you may:
  • Use the arrow keys to navigate around the grid.
  • Use the number and letter keys to enter a value in the highlighted cell.
  • Press the space or Delete key to remove any values from the highlighted cell.
  • Press the "P" key to toggle between Pen and Pencil or use the mouse wheel (if not in Active Number mode - see below).
  • Press the "U" key to undo last input.
  • Hold Shift key down to always enter in pencil (not operable with the number pad).

Other Tips

  • Click the Undo icon (yellow arrow) to undo last input. You can undo all the way back to the beginning.
  • Holding the Shift key when clicking on a number in the input panel will pencil that number in. You may find this more convenient than toggling between the Pen and Pencil icons.
  • To remove just one pencilled number in a cell, enter that number again.
  • To remove all pencil numbers in a cell, either click the eraser button or simply "pen" the final choice in.
  • To remove all pencil marks from all cells, use the menu option under "Edit".
  • There is an alternate mode of number input via the mouse called "Active Number Mode" (see below).

Active Number Mode

If you select this mode (via Preferences menu option), then the number you click from the Number Pad becomes the "active number". Clicking on any cell will enter it in that cell. This is the reverse of the "cell select" mode, where you highlight a cell and then select the number to input. Those that prefer to solve by focusing on one specific number at a time will find this mode much more convenient.

To change the active number, select a new one from the Number Pad or scroll the mouse wheel down/up to increase/decrease the number. (If not in Active Number Mode, the mouse wheel will toggle between pen and pencil.)

In Active Number mode, all pencil functionality remains the same as does the ability to use the keyboard.

Description Of Menu Options

New Puzzle Menu

Main options to do with generating new puzzles.

The first three options will generate a puzzle at four different difficulty levels. There is one new puzzle at each level per day.
The third level - Hard - will require more advanced strategies to solve.

Note: All puzzles are solvable by pure logic - no guessing required!

Input Archive Puzzle #
This option allows you to play a puzzle that has been generated before. Every generated puzzle has a unique number (displayed in top right). This option is useful for challenging friends to solve the same one you did.

Edit Menu

Undoes the last input. You can undo right back to the beginning of the puzzle (unless you loaded a partially solved one). There is an Undo button which performs the same task, also the "U" key is a shortcut to this option.
Clear Possibles
This will clear all possibles displayed in the grid.
Clear All Input
This will clear all input (pen and pencil marks) displayed in the grid.
Pencil Marks to Pen
This option will convert all cells that have one pencil mark to a pen mark. The "C" key is a shortcut key for this option.
Saves the current state of the puzzle to temporary user data on this computer. This is useful if you wish to come back another time to continue solving it, or if you are guessing which may necessitate you to backtrack later on.
Loads the last saved puzzle on this computer.
This will print the puzzle at the state it is currenly displayed in the grid.

Solve Menu

Main options to aid in solving puzzles.
Check My Solution
Checks to see if you have solved the puzzle correctly. Any errors made will be shown in red.
Suggests which cell may be the next easiest to solve. It will not fill in the value - for that you need to select the "Solve One Cell" option.
If a cell is solvable via basic solving techniques, then the clue will suggest you look where a particular number is located in a block, row or column and will highlight that area of the grid. This helps you more than the "Hint" option and is the easiest aid you can ask for, save getting the actual answer.

If the only way to solve a cell is via more advanced solving techniques (as found in Hard and Tough puzzles), then the clue will point you to the cell and say what technique(s) is/are required. This is not as helpful and you may need to resort to the "Solve One Cell" if still stuck.

Solve One Cell
This is a very powerful option, especially as a learning tool. It will fill in one of the cells and displays the reason why that number is the answer to the cell. In the case of advanced techniques, it will walk through the steps to solve the cell. (Still to be implemented)
This option will show you the possible numbers for each unsolved cell using logic techniques based on the puzzle level.
Solve the puzzle and shows the completed solution.


Here you may set various preferences. They are remembered and will reload from what was last set on that computer.

Active Number Mode: This toggle Active Number Mode, described above.

Show Timer: Toggles display of timer.

Show Pen/Pencil Cursor: Toggles whether the pen/pencil cursor is displayed over the grid or just the standard finger cursor. (Does not apply if Active Number Mode set as the cursor changes to the active number and will be gray if pencil mode.)

Auto Show Errors: If checked, as you enter a number in a cell, it will display in red if incorrect.

Auto Remove Pencil marks: If checked, when you enter a final (pen) number in a cell, that number will be automatically removed from the possibles in all other cells in same row, column or block.

Sound Effects: Toggles sound on/off.

When Select Num Show All Its Cells: If checked, when you click on a number on the Number Panel, it will highlight all the cells that contain that number. (Does not include pencil numbers.)

De-emphasize Completed Numbers: If checked, when all 9 of a number have been entered correctly, that number will be de-emphasized on the Number Panel. You can still select the number, though.

You can also customize the color of the grid and the numbers.