These are discovered with logic and require no guessing.

There are exactly one of each number 1 to 9 in the grid.

No row or column can add up to more than 9.

Starting with the given solution number, rule out numbers in its row and column that would violate the "More than 9" rule.

As you eliminate numbers, other eliminations will become logically dedutable.

How to Play

Touch or click on a cell in the grid to change the state of that number. Once to remove the number. Twice to set it as a solution. Three times to reset.

The puzzle is solved when there are 9 circled numbers with all other numbers are ruled out.

Use the remaining numbers in the grid at the bottom to help target numbers.

Strategies

Use the number grid below the puzzle to determine numbers that only have a few remaining options.

If a number can only be in a few places, check for numbers that can rule them all out.

Since there must be at least one of each number 1-9 in the puzzle, any number that rules out all of the remaining options can itself be removed.

Sometimes the given number at the start of the puzzle will appear in multiple places. These duplicates can all be removed.

If there is only one remaining number, it must be a solution.

Each row and column will have at least one solution number. (Some may have more.)

When 9 is a solution, all other numbers in its row and column can be removed. (Since any of them will violate the "More than 9" rule.)

When 8 is a solution, all numbers except "1" in its row and column can be removed. And so on...