Dominosa Domino Logic Unblocked

Dominosa Domino Logic is a puzzle of reconstruction. Imagine someone tipped a full box of dominoes onto a table, arranged them into a neat rectangle, copied every number onto paper, and then swept the tiles away. That paper is all you get. From it you must work out where each domino lay, knowing that the set contained every pair exactly once. It is Simon Tatham’s version of a puzzle usually credited to O. S. Adler, and it plays unblocked in your browser with mouse, keyboard or touch.

The Set and the Grid

The default board uses the numbers 0 to 6. One domino exists for every pair, doubles included, so the set holds 28 dominoes and fills an 8x7 grid. Each domino covers two squares that sit side by side or one above the other.

Clicking the boundary shared by two neighboring numbers puts a domino over them. Click it again to lift it. Laying a domino across squares already in use removes the old ones automatically. A right-click on a boundary marks it with a small stroke, your own reminder that no domino may sit there.

The board is complete once all cells are filled and each pair shows up a single time. Any repeated pair turns red at once.

Four difficulty levels, Trivial, Basic, Hard and Extreme, control how deep the logic goes. All of them have a single correct answer.

Dominosa Domino Logic controls

To do this	Keyboard	Mouse	Touch
Lay or lift a domino	Arrow keys to a spot between two numbers, then Enter	Left-click between two neighboring numbers	Tap between two neighboring numbers
Draw or erase a "not here" line	Space	Right-click between two numbers	Press and hold between two numbers
Light up every copy of a number	Type the number	Right-click on the number	Press and hold on the number
Undo, redo or deal a new grid	U / R / N	Undo move, Redo move and New game buttons	Undo move, Redo move and New game buttons

A Solver’s Toolkit

Most Dominosa logic comes down to two questions asked over and over: where can this square go, and where can this pair go?

Squares with one exit. A square in a corner, or one boxed in by placed dominoes, may have only one free neighbor left. It has to pair with that neighbor.

Pairs with one home. Choose a pair, such as 1-4, and scan the grid for every place a 1 sits next to a 4. If there is only one, place it. Typing a number highlights all of its copies, and you can highlight two numbers at a time, which makes this scan quick.

Clean up after each placement. When a pair is used, mark off each remaining place that pair might have fitted. Those lines often leave neighboring squares with a single exit, which starts the next chain.

Doubles are rare. Two equal numbers next to each other are the only candidate for that double, unless the same double appears elsewhere. Check doubles early.

Late game. On Hard and Extreme, simple scanning eventually stalls. Look for a pair with exactly two possible spots that share a square. Whichever spot is right, that square belongs to this pair, so you can rule out every other domino that would cover it.

Why It Clicks

The rules fit in one sentence, yet the bigger sets feel like untangling a knot. If you like this style of number logic, try Magnet Dominoes for another domino-based grid, or Math Cage Grid for arithmetic deduction.