Deep Night Sudoku

How to Play Deep Night Sudoku

A Sudoku game to enjoy in the quiet atmosphere of the night. Fill every cell with numbers from 1 to 9 so that no number is repeated in any row, column, or 3×3 block.

Select an empty cell and enter a number from 1 to 9 using the number buttons at the bottom of the screen.
Each row, column, and 3×3 block must contain the numbers 1 to 9 exactly once.
If you enter an incorrect number, it will immediately be shown as a mistake.
Turn on "Notes" to write small candidate numbers that may fit in a cell.
Press "Erase" to clear the contents of the selected cell.
Press "Undo" to cancel your previous action.
If you are unsure how to proceed, press "Hint" to see a solving technique that can be used on the current board.
Fill every cell with the correct number to clear the stage.

Sudoku Solving Techniques

Naked Single

If only one candidate remains for a cell, that number can be confirmed. This is one of the most basic Sudoku solving techniques.

The only candidate for this cell is 9, so 9 can be placed here.

Hidden Single

If there is only one cell in a row, column, or 3×3 block where a certain number can be placed, that number can be confirmed in that cell.

Only one cell in this row has 5 as a candidate, so 5 must go in that cell.

Locked Candidates

This technique can be used when all candidates for a certain number within a 3×3 block are confined to the same row or column. That number can then be eliminated as a candidate from cells in the same row or column outside the block.

In the upper-left 3×3 block, the candidates for 7 are confined to the second row. Therefore, 7 can be eliminated from cells in the same row outside the block.

Naked Pair

If two cells in the same row, column, or 3×3 block contain exactly the same two candidates, those two numbers must occupy those two cells.

These two cells form a Naked Pair with 2 and 8, so 2 and 8 can be eliminated from the other cells in the same row.

Hidden Pair

If two numbers can only appear in the same two cells within a row, column, or 3×3 block, those two cells must contain those two numbers.

In this row, 3 and 7 can only be placed in the two blue cells. Therefore, all candidates other than 3 and 7 can be eliminated from those two cells.

Naked Triple

This technique can be used when the candidates across three cells in the same row, column, or 3×3 block are limited to a total of three different numbers.

The three blue cells use only the numbers 1, 4, and 6. Therefore, 1, 4, and 6 can be eliminated from the other cells in the same row.

X-Wing

If the candidates for a certain number in two rows appear only in the same two columns, that number can be eliminated from the other cells in those two columns. The same technique can also be applied with rows and columns reversed.

The candidates for 6 in rows 2 and 7 appear only in columns 3 and 8. These four cells form an X-Wing, so 6 can be eliminated from the other cells in columns 3 and 8.

Deep Night Sudoku can also be played on mobile devices.
Scan the QR code.

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