How to play Cluster Count
Shade squares so every circled number equals the total size of all the shaded groups touching that circle. Also known as Kurotto, Group-size shading puzzle.
The rules
- Circled squares are never shaded.
- A group is a set of shaded squares joined side by side.
- A circle’s number is the total number of squares in all the groups that touch it along a side.
- Squares without circles may be shaded or white, as the numbers require.
Playing Cluster Count on Puzzle Solvers
- Choose a size and a difficulty, then press New Puzzle.
- Tap a square to shade it, again for a dot (white), again to clear. Drag to do several.
- A circle turns green when the groups touching it add up exactly, red when there’s too much.
- Hint explains the next deduction — circles that are full, that can only grow one way, or that would overflow.
Using the Cluster Count solver
- Choose the size and type the circled numbers (or press Sample).
- Press Solve and step through: full circles, overflowing groups and forced growth.
A worked example
A 1 in a corner with one neighbour already white: its other neighbour must be the single shaded square, and the squares around that square are white.
Two circles side by side, a 2 and a 5: a group touching both counts for both, so the 2 can only touch a group of at most two.
Strategies
- Zeros. A 0 means all four neighbours are white.
- Full circles. Once the groups around a circle add up to its number, every square that could join them is white.
- Overflow. If shading a square would merge groups into too many squares for a nearby circle, it is white.
- One way out. A circle that still needs more and can only grow through one square shades it.
- Shared groups. One group can touch several circles — it counts in full for each of them.
Common mistakes
- Counting only the shaded neighbours instead of the whole groups they belong to.
- Counting the same group twice for one circle.
- Forgetting that diagonal squares don’t touch.
Where it comes from
Group-size shading puzzles come from the Japanese pencil-puzzle tradition of the 2000s.
Frequently asked questions
Do diagonal squares count as touching?
No — only squares that share a side.
Can a group touch two circles?
Yes — and its whole size counts for each circle it touches.
Is there always one answer?
Yes — every puzzle here is checked to have exactly one solution.
How do I solve one from a book?
Open the Cluster Count Solver, type the circled numbers and press Solve.
Keep going
- Play Cluster Counta fresh puzzle every time
- Cluster Count Solverstep by step, every move explained
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