Dominosa Puzzle Online

Dominosa is one of the classic one-player logic games in Simon Tatham's Portable Puzzle Collection. Tile the rectangle with a full set of dominoes.

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Preparing the game board and controls.

Game Objective

Divide the grid into dominoes, each covering two adjacent numbers. Every number pair must appear exactly once: 1-3 and 3-1 count as the same pair, and doubles such as 2-2 are included.

Tile the rectangle with a full set of dominoes.

How to Play

Click the edge between two neighboring numbers to place or remove a domino over those two squares.
Right-click an edge to draw a separator when you know those two squares cannot be one domino.
If matching dominoes turn red, the same number pair has been used more than once.
These puzzles reward careful deduction more than speed. Start with the most constrained clues, eliminate impossible choices step by step, and avoid guessing unless the puzzle specifically calls for it.

Beginner Tips

Start by listing rare pairs. If a pair appears in only one adjacent place on the grid, that domino is forced.
Each square belongs to exactly one domino. If a square has only one possible neighbor left, connect it.
A red duplicate does not tell you which one is wrong, but it tells you that at least one domino with that same pair must be removed.