Expert tips

Technique 1: Naked Single

A Naked Single occurs when a cell on the grid can only be reached by one domino. No other domino can physically cover that cell, perhaps because the surrounding cells are already filled, or the cell sits in a corner with only one open neighbour.

When you spot a Naked Single, place that domino immediately. It's the most basic technique and appears in every Easy puzzle. Scan the edges and corners of the grid first, since cells with fewer neighbours are more likely to be Naked Singles.

Technique 2: Rule Forces Domino

Sometimes a rule directly determines which domino must go in a region. A two-cell 'all equal' region can only be filled by a double domino (0-0, 1-1, 2-2, etc.). A two-cell '=12' region can only be filled by a 6-6. A two-cell '<1' region must be 0-0.

These forced placements give you certainty from the start. Identify them before anything else. They anchor the rest of the solution and often trigger a cascade of other forced moves.

Technique 3: Hidden Single

A Hidden Single is a domino that can only go in one position on the entire grid, even though that position could theoretically accept other dominoes too. The key insight is that all of the domino's other possible positions are blocked by placed dominoes, grid edges, or rule violations.

To find Hidden Singles, pick a domino from the drawer and mentally check every position it could go. If only one works, place it. This technique is the backbone of Medium puzzles.

Technique 4: Rule Elimination

Rule Elimination narrows down placements by checking which dominoes satisfy a region's rule. Say a region requires '=8' across two cells and three dominoes could physically fit there. Two of them would produce sums that don't equal 8. Only one works, so place it.

This technique combines physical constraints (which dominoes fit) with rule constraints (which ones satisfy the rule). You're often checking both halves of a domino against two different regions simultaneously.

Technique 5: Implication Chains

Implication Chains are the advanced technique that separates Hard puzzles from Medium ones. You assume a domino goes in a particular position and trace the consequences. 'If this 3-5 goes here, then that region needs a 2 from the remaining domino, but the only domino with a 2 can't reach that cell. Contradiction. So the 3-5 doesn't go here.'

These chains can be two or three steps long. The key is to be systematic: follow each assumption to its conclusion and look for the contradiction that tells you the assumption was wrong.

Work from constraints, not guesses

The single most important habit: never place a domino unless you know it's correct. Instead of trying random placements, figure out where each domino can't go. Check rule violations for both halves. The fewer valid positions a domino has, the closer you are to placing it with certainty.

Guessing leads to cascading errors. One wrong placement changes the constraints for every other domino, sending you down a path that ends in contradiction. Work from what you know, not what you hope.

Solve the tightest rules first

A region requiring '=0' across two cells? That's a 0-0 domino, full stop. '=12' across two cells? Only 6-6. 'All different' across three cells with two already filled? The missing value is fixed. Tight constraints give you certainty, so start there.

Once you place one domino with certainty, it removes that domino from the drawer and tightens every other region it touches. The puzzle unravels from the tightest point outward.

Use doubles as anchors

Double dominoes (0-0, 1-1, 2-2, 3-3, 4-4, 5-5, 6-6) are special because both halves carry the same pip value. In 'all equal' regions with two cells, only doubles work. This makes them easy to place early.

Placing doubles early is powerful because they anchor the grid. A double placed in a region often forces the pip values in adjacent regions, triggering a chain of deductions that can solve large sections of the puzzle.

Think about both halves of each domino

Every domino placement affects two cells, and often two different coloured regions. A domino might satisfy one region's rule perfectly while violating the rule in the other region it touches.

Before placing a domino, always check both halves. Ask: does the left pip work for its region? Does the right pip work for its region? What about the rotated orientation? Would swapping the two pips make it work? This double-check catches mistakes before they cascade.

Count the available pips

Each puzzle gives you a fixed set of dominoes. Once you've placed all the halves showing a 6, no remaining domino can contribute a 6 anywhere on the grid. Tracking which pip values are still available in the drawer eliminates impossible placements across the whole grid.

The Drawer Sort button arranges your remaining dominoes by pip value, making it easy to see at a glance which values are still in play.

The solving tools

The Pip Counter is a built-in tool that totals the pip values already placed in each coloured region. Instead of counting dots manually, glance at the counter and focus on what's still needed.

For a region with an '=10' rule that already contains pips summing to 7, you know the remaining cells must contribute exactly 3 more. The Pip Counter turns arithmetic into pattern recognition, and it updates automatically as you place dominoes.

The Sum Helper works alongside the Pip Counter for sum-based rules. It shows the difference between the current pip total and the target, the gap you still need to fill.

Compare the gap against the dominoes remaining in your drawer. If a region needs 5 more pips across two cells, check which remaining dominoes have halves that sum to 5, and which of those can physically reach those cells. Sometimes only one combination works.

Common mistakes to avoid

The most common error is forgetting to check both halves of a domino. Placing a domino that satisfies one region but violates the other wastes time and creates confusion downstream.

Another common mistake is tunnel vision: focusing on one area of the grid and missing a forced placement elsewhere. After each move, briefly scan the whole grid. A placement on one side of the grid can create a Naked Single on the opposite side.

What to do when you're stuck

Every puzzle is solvable through logic, so if you're stuck, there's a deduction waiting to be found. First, re-scan the grid for Naked Singles. A placement elsewhere might have created one. Next, check each remaining domino: can it only go in one place? Then look at regions where most cells are filled, because the remaining constraints may have tightened.

If you're still stuck, use the hint system. The first hint highlights any incorrectly placed dominoes. The second removes them. The third places the next correct domino. Hints guide you without revealing the whole solution.