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Checku is a logic puzzle combining chess and sudoku.
The goal
Fill the board so that every row and column contains exactly the set of pieces shown in the selection bar. Empty squares count too, each row and column must have the right number of them. And one more rule: no king may be in check.
Each puzzle has exactly one solution.
Placing pieces
Drag a piece from the bar below the board onto a square. To remove a piece, drag it off the board.
Click a piece in the selection bar to select it, then click a square to place it. Click the selected piece again to deselect it. Click and drag also works.
To mark a square you believe is blank with a dot, tap it — or drag the blank tile onto it.
To mark a square you believe is blank with a dot, click it with no piece selected — or select the blank tile and click the square.
A 
placed here puts the 
in check. This square cannot be a
placed here puts the in check. This square cannot be a Pawns attack in their normal directions. A cannot be placed diagonally below this 
cannot be placed diagonally below this 
Sometimes checks can be blocked by adding a piece