Dominosa
Tile the number grid with the full set of dominoes, each pair used once.
How to play Dominosa
The grid is printed with numbers, and you must cover it completely using a full set of dominoes. That set contains every possible number pair once (for a grid of 0 to 3 that is ten dominoes, from double-zero up to double-three) and each pair may be used only a single time. Place a domino by clicking the line between two neighbouring cells, or by dragging from one cell onto the cell beside it; it snaps into a capsule that spans both. If a domino overlaps one you already placed, it simply replaces it, and any pair you have used twice is dimmed so you can spot the clash. The board is solved when every cell is covered and each number pair has been used exactly once. Every puzzle has a single solution, so it can always be reached by logic. Beat your best time.
Turning numbers into dominoes
You start with a grid of bare numbers and one guarantee: it can be tiled by a complete domino set, every pair used exactly once. For a 0-to-6 board that is the familiar 28-piece double-six set; the smaller 0-to-3 board uses ten dominoes, from double-blank up to the 3-3. The catch that makes it a puzzle rather than a jigsaw is that each pair may appear only once, so the whole board hinges on where the duplicates are allowed to sit.
The cleanest way in is to hunt for pairs that can only be made in one place. Run down the set of dominoes you have to place, and for each one count how many spots on the grid actually show those two numbers side by side. If a pair like 2-5 lines up in exactly one spot, that domino is forced: lay it, cross 2-5 off your list, and every other 2 next to a 5 on the board is now just two strangers passing. Then check the cells around the piece you placed, because each of them just lost a possible partner and may have only one left.
Start with the doubles
The doubles are the easiest tiles to pin down, so hunt them first. A double-six needs two 6s touching, and that happens in far fewer places than a 6 touching some other number. Scan the grid for every spot where equal numbers meet. If the only place two 6s touch is down in a corner, the 6-6 lives there and the puzzle just got smaller. Doubles pay twice, too. Once the 6-6 is placed, any other pair of touching 6s can never be a domino, which often forces how those cells pair off with their remaining neighbours. On a full 0-to-6 board there are 56 cells and every value appears exactly eight times, so each double has only a handful of homes to check. Work through all the doubles and the mixed pairs usually start locking themselves in. One warning: if two 6s touch in several places, leave the 6-6 for later. Forcing it early on a hunch is the one habit that plants contradictions you will not notice until the last corner refuses to fill.
A working method
- Track which pairs you have used. A pair placed twice is illegal, and the game dims any duplicate so a clash is easy to spot and fix.
- Look for lonely cells. A number tucked in a corner or against an edge may have only one neighbour it can pair with, which fixes its domino at once.
- Placed dominoes are walls. Each one you commit removes options from its neighbours, so re-scan the area every time you lay a piece.
- Every puzzle has one solution, so you never need to guess. If two placements look equally good, you are missing a deduction, not facing a coin flip.
Placing the pieces
Click the line between two cells to drop a domino across them, or drag from one cell onto its neighbour. A new domino laid over an old one simply replaces it, so fixing a mistake is quick, with no need to clear first. The board is solved when every cell is covered and each number pair has been used once and only once. It is a quiet, methodical puzzle, and the click of the last domino snapping into place is the whole reward.
A puzzle from 1874
Dominosa has been around far longer than the browser. The puzzle is credited to O. S. Adler in 1874, and it has resurfaced ever since under names like Domino Hunt and Domino Solitaire, first in newspaper puzzle corners and later among programmers; it is one of the games in Simon Tatham's well-known Portable Puzzle Collection. Setters tune the difficulty by changing the range, which is why a 0-to-3 board feels like a warm-up and a 0-to-6 board like an afternoon project. The long life makes sense. Dominoes themselves are centuries older, and the idea of running the logic backwards, from a field of numbers to the tiles that must have made it, is the kind of inversion puzzle-makers cannot resist. The uniqueness promise is the modern polish. Because exactly one tiling exists, every position you reach has a next deduction waiting somewhere, and finding it is the whole game.
Dominosa leaderboard
Top scores. Log in to compete.
- Loading leaderboard…
Dominosa: frequently asked questions
What is the goal in Dominosa?
You cover a grid of numbers with a complete set of dominoes. Each domino must sit on two adjacent cells whose numbers form its pair, and every unordered pair from the set is used exactly once, with the whole grid covered.
How do I place or remove a domino?
Click the border between two adjacent cells, or drag from one cell to a neighbour, to drop a domino there. Clicking the same domino again removes it, and placing one over existing cells replaces whatever was there, so it is easy to correct mistakes.
Why is one of my dominoes dimmed?
A dimmed domino means its number pair is already used elsewhere on the board. Since every pair may appear only once, you will need to move one of them before the puzzle can be solved.
Is every Dominosa board solvable?
Yes. Each board is generated and verified by a solver to have exactly one valid tiling, so a careful, logical approach will always crack it without guessing.
How many dominoes am I placing?
As many as a full set for the grid's range. A 0-to-3 board uses ten dominoes, a 0-to-6 board twenty-eight. The set contains every number pair once, from the double-blank up to the highest double.
What does it mean that each pair is used once?
The domino set has exactly one tile for every unordered pair of numbers. So there's a single 2-5, a single 3-3, and so on, and your covering must use each of them precisely once.
How do I find a domino that's forced?
Look for a pair that appears side by side in only one place on the grid. Since that pair's tile has to go somewhere and there's just one spot, it must sit there: place it and rule that pair out elsewhere.
What happens if I place a domino wrong?
Dragging or clicking a new domino over an existing one replaces it, so you can correct without clearing first. Any pair you've used twice is dimmed, flagging the clash for you.
Do I ever have to guess?
No. Every puzzle has a single solution reachable by logic. When you feel stuck, look for a forced pair or a cell with only one possible partner rather than guessing.
Which dominoes should I try to place first?
The doubles. A double needs the same number twice side by side, which happens in far fewer places than a mixed pair, so doubles are often forced straight away. Pin the doubles down first and the mixed pairs around them tend to fall in on their own.
Is Dominosa free to play?
Yes. Dominosa is completely free on Inkplay, with no download, no sign-up, and no in-game purchases. Open the page and play instantly on desktop or mobile.
Can I play Dominosa unblocked?
Yes. Dominosa runs entirely in your browser with no download, install, or plugins, so it loads instantly and keeps working even on school or work networks where bigger game sites get blocked.
More games to play
In the mood for more? Try 2048, Memory Match, Lights Out, Minesweeper, or browse all puzzle games and the full games list on Inkplay. Dominosa also appears in Logic Puzzles.