Time
0:00
Best
—
A pure-logic domino puzzle. The grid is filled with numbers; split it into a complete set of dominoes so that every number pair appears exactly once. Each board has one unique solution — no guessing, just deduction. How fast can you finish?
Every cell holds a number from 0 to 5. Your task is to draw the borders that split the whole grid into dominoes, where each domino covers two side-by-side cells and shows a pair of numbers.
The catch is that the dominoes must form one complete double-5 set: there is exactly one 0-0, one 0-1, one 3-5, and so on — twenty-one pairs in all, each used once and only once. So if you have already placed a 2-4 domino somewhere, no other domino may be a 2-4.
Drag between two neighbouring cells to lay a domino across them, and tap an existing domino to take it back off. If you ever use the same pair twice, both of those dominoes glow red so you can spot the clash. Every puzzle has exactly one valid solution, reachable by logic alone. Solve it as quickly as you can — your time is your score.
Start from the pairs that can only sit in one place. Scan the edges and corners: a number tucked in a corner has only one or two neighbours, so the domino covering it is often forced. Lay every forced domino first and the rest opens up.
Use the once-only rule as a weapon, not just a constraint. If a 5-5 can only be formed in a single spot on the whole board, place it and rule out 5-5 everywhere else — which in turn forces other dominoes near those fives.
Watch for lonely cells. As you place dominoes, a cell can end up with every neighbour already taken; the move that would have stranded it must be wrong. Keep an eye out for any square about to be boxed in with no partner left.
Let the red glow guide you, but don't lean on it. A red clash tells you a pair is duplicated, yet it won't say which of the two is the real one. Treat it as a nudge to recheck that pair's other candidate spots rather than a full answer.