Example puzzle

This is an example puzzle. You can solve it the same way as you would solve competition puzzle, but result never stored. You can reveal an answer for the puzzle by clicking "Show answer" link.

Double Sudoku

Author: Andrey Bogdanov

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Place a digit from 1 to 4 in each empty cell so that each digit appears exactly twice in each row, column, and outlined region. Identical digits cannot share an edge.

Example puzzle

Grid control: Click at a cell reveals the value chooser. Click at the selected value changes the state of the cell. More details about grid control are at the help page.