Link to this puzzle: by game ID by random seed
Tile the rectangle with dominoes (1×2 rectangles) so that every possible domino appears exactly once (that is, every possible pair of numbers, including doubles).
Click between two adjacent numbers to place or remove a domino. Right-click to place a line between numbers if you think a domino definitely cannot go there. Dominoes light up red if two identical ones appear on the grid.
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