It differs in that it displays a number for each row and column. This number is the total of the cell contents that are between the "1" and the "9" for the corresponding row/column.

For example, in the puzzle to the right, in row 3 the sum of digits between the "1" and "9" must be 4. There is only
one combination that gives 4 (ie the digit 4 itself) so the cell to the right of the "1" must be a "4" and the cyan colored cell must be a "9".
Similarly, in row 5 the total must be 32. The only possibility for that is a combination of the digits "245678" ie 6 cells.
So the "9" can only be in the cyan colored cell and the cell in column 1 has to be a "3".

It is recommended that you watch the video walkthrough to get tips
on solving strategies.

- There is one new puzzle per day which is automatically loaded when you open the page.
- 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.
- 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).

- Clicking the Sandwich total numbers at the end of each row or below each column will show all the possible digit combinations that sum to that number. Of course the digits may be in any order in the sandwich cells (ie those cells between the "1" and "9").
- For every row or column, the sum of the digits (1-9) equals 45. So all the non-sandwich cells for a row or column will equal (45 - sandwich total - 10) (the 10 is the sum of "1" and "9"). That is, all cells outside of the "1" and "9" will total (35 - sandwich total). If for example there are 3 non-sandwich cells and you wish to know the digit combinations that make that total, you can use the button to see combinations for any total and number of cells.
- 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 the Active Number mode, all pencil functionality remains the same as does the ability to use the keyboard.

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

**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.)

**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.

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

If the only way to solve a cell is via more than one step using Sandwich total solving techniques, then the clue will point you to the cell and you may need to resort to the "Solve One Cell" if still stuck.