- 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.)

- Use the arrow keys to navigate around the grid.
- Use the number keys to enter a number in the highlighted cell.
- Press the space or Delete key to remove any numbers 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.
- Press the "C" key to change all cells with one possible (pencil mark) to pen.
- Hold
**Shift**key down to always enter in pencil (not operable with the number pad).

- 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).

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.

Score = Rating + TimeBonus - Accuracy - SolveAids

where:**Rating**= the rating index assigned to each puzzle. This index attempts to measure the difficulty of the puzzle by examining at each stage of the solving process how many cells can be solved by logic relative to the number of unsolved cells. It also looks at what techniques are required to solve those cells. Those that rely on more sophisticated techniques greatly increase the rating index. The current difficulty level (Easy, Medium, Hard, Tough) is only based on the techniques required to solve and you may now find that some Easy puzzles have a higher rating than other Medium ones or similarly for Medium/Hard/Tough.**TimeBonus**= extra points for completing the puzzle quickly. In fact, time is still the most important factor determining your score. The time bonus is computed by taking the average time per difficulty level divided by your time and then multiplied by the rating index. For example, the average time for Medium puzzles is currently set at 11 minutes (660 seconds) so if you complete a puzzle with a rating of 1100 in 6 minutes, you will score a time bonus of (660/360 * 1100), ie 2017. If you completed the puzzle in 20 minutes (1200 seconds), your time bonus would be (660/1200 * 1100) ie 605.**Accuracy**= the number of errors you make. Errors are only recorded when you enter an incorrect value and then enter a value in another cell. So, if you accidentally enter an incorrect number and immediately correct it, no error will be recorded. For the first error you lose 30 points, for each subsequent error the points lost increases by 10. So you would lose 40 points for the second error and so on. Note that pencil marks do not affect the scoring in any way.**SolveAids**= each time you use a hint or clue or check your input. You lose 40 points for each hint, 50 for each clue and 20 each time you check your input. Warning! If you set "Auto Show Errors" preference, it will give you a check penalty after each input.

- You use the "Solve", "Solve One Cell" or "Possibles .." options from the Solve menu.
- You save the puzzle and then reload.
- You print the puzzle.
- You do not complete the puzzle.

The first four options will generate a puzzle at four different difficulty levels.

The first two levels - Easy and Medium - will generate a new puzzle on demand.

The third level - Hard - will generate a new puzzle every hour and will require more advanced
strategies to solve.

The fourth level - Tough - will generate a new puzzle every day and provide even more challenging puzzles.

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

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.

It is recommended you do the Sudoku Tutorials first to understand the terminology used and an explanation of the solving strategies.

**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.)

**Show Possibles In Grid:** If set, the possible numbers for each cell will be displayed in a 9 point grid format,
else will be displayed next to each other. (Only for HTML5 version)

**Auto Resize Grid:** If checked, the grid will resize according to your browser height. Press F11 for full screen to achieve maximum size.

**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.