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You can select cells by pressing on them. If you hold down your mouse and drag, you can select several.

You can also press ctrl (or cmd on mac) and press on cells, which will then add them to your selection.

You can also use your mouse arrows to move around the grid.

You can use the following shortcuts:

- z for numbers
- x for cornermarks
- c for centermarks
- v for colors
- b for notes

You input a number or a value, by selecting one or more cells and pressing a number from 0-9 or by pressing the numbers on the controller on the right. Press the backspace button to remove the value

You create cornermarks by selecting a cell and pressing the numbers you want to mark. You can use both the keyboard and the controls on the right. Press the backspace button to remove the cornermarks

You create centermarks by selecting a cell and pressing the numbers you want to mark. You can use both the keyboard and the controls on the right. Press the backspace button to remove the centermarks

You add colors like you add numbers. The numbers 0-9 match the colors on the right, if you want to use your keyboard instead. Press the backspace button to remove the color

You can add notes as annotations to any cell to record information that cannot be communicated using the standard pencil mark tools. Cells with with notes will display a marker in the top right corner. Hovering over the marker will show the saved text. Press the backspace button to remove the note

The scanning tool can be used to help solve the puzzle by checking whether any cells are restricted to a single digit due to the puzzle rules, or to quickly clean up pencil marks after placing a digit. With Auto-scanning enabled, the scanner will run immediately every time a digit is entered - editing pencil marks will not trigger a scan.

Press (s) to start or stop the scanner.

Press (a) to make a single step.

Press (h) to toggle highlighting on or off.

Press (t) to toggle Tuple highlighting on or off

*Highlighting Mode**None*: No additional cells are highlighted when the selected cells in the grid are changed.

*Seen*: Highlight any cells which are seen by the currently selected cell. If multiple cells are selected, only those cells seen by every cell in the selection are highlighted.

*Tuples*: Highlight any cells which form a Tuple with the currently selected cell.*Scanning Mode**Basic*: The scanner will only use the basic rules of Sudoku when checking available digits.

*Advanced*: The scanner can use the puzzle clues when checking available digits.

*Extreme*: The scanner can use global negative constraints when checking available digits.*Options*Depending on the scanning mode and the puzzle constraints, you can choose which types of clues can be used by the scanning algorithm.

*Scanning Speed*Control how fast the scanner runs.

The walkthrough is accessed by clicking the icon with the walking person below the controller. When playing a game, you can follow along in the modal, or you can press the button in the top right corner to open the walkthrough in a new tab. If you are creating your own puzzle the same modal can be used to create a walkthrough.

If you don't want to open the modal everytime you want to add a step, you can use the "w" shortcut, which will add the step for you. To add a description you still have to open the modal, though.

Okay

Info: We automatically save your walkthrough whenever you save your sudoku puzzle

Add step to walkthrough

The shaded square in c8 must be a 3, since every digit except the shaded digit in row 8 contributes to either the 15 sum or the 27 sum. Since 45-15-27=3, the shaded square is 3.

r3c8 cannot be shaded. If it was shaded, it would have to be 3, and since r3c9 cannot be 3, the 3 clue would not be able to be satisfied.

Since we cannot have 1 digit satisfy the 3 sum, we must have 2: 1+2=3. Thus we can place a shaded square in r3c7.

r5c8 must be shaded, because otherwise the 15 clue would see 5 squares or more. The minimum sum of 5 squares it sees would be 1+2+4+5+6=18, which is larger than 15. (Remember that it cannot see a 3, since we know the shaded square is a 3.)

The 44 clue lets us place 1 for free in r7c9.

The 8 clue must be satisfied by a 35 pair.

3 in box 3 must go in r7c12 (it cannot go in the shaded square since we already have a shaded 3). Therefore, the 11 clue must be satisfied with a 38 pair.

We can shade r6c6 because if the 31 clue sees 4 squares or less, the maximum sum would be 9+8+7+6=30.

Also, we can place 9 in the squares the 31 sees, because otherwise, the maximum sum would be 8+7+6+5+4=30.

r1c5 must be a 9 and r2c5 must be shaded, because if any other available square in c5 was shaded, the sum would be much larger than 9.

We can shade r1c3 because the 11 clue must see at least 2 squares.

We can shade r8c1. If the shaded square in c1 was r4c1, then the maximum sum would be 9+8+7=24, and if it was in r9c1, the minimum sum would be 45-9=36.

Finish shading. (I got rid of the negative shading in red because it is no longer necessary.)

Realize that 45-29=16=7+9, so we must have a 79 pair that is not seen by the 29 clue.

If r1c9 is a 9, then no shaded square can be a 9, contradiction.

So instead it must be a 7.

9 must go in the blue highlighted squares because the minimum sum of the other three squares that 15 sees is 1+2+4=7, and 7+9=16. 8 must also go in these highlighted squares because of Sudoku.

Since 27-8-9=10, we need another pair of digits that add to 10. The only available pair is 4+6, so now we have a 4689 quadruple.

Sudoku.

The blue cells must be 56. Also, the purple cells must be 1236. (These are the only sets that give our desired sums.)