GridMewThe rules, one cat at a time
Learn the row, column, region and no-touch rules, and make your first moves.
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Four checks for every catUse the two tools deliberatelyFinish without guessingApply the ideaOriginal exampleCheck your understandingOriginal GridMew lesson · Updated 16 October 2026
Learning goal: Check a proposed cat against all four constraints, rather than accepting a cell because its color looks available.
Four checks for every cat
Fill an n×n board with exactly n cats. Each horizontal row needs one cat, each vertical column needs one cat, and each connected, lettered region needs one cat. A cell belongs to all three groups at once. A placement must satisfy all three quotas, not just the region color.
Cats also cannot touch along an edge or at a corner. The eight cells immediately surrounding a cat are unavailable. A cat farther away on the same diagonal is allowed: this is not the classic eight-queens diagonal rule.
Use the two tools deliberately
Choose Place cat, then click or tap a cell once. Choose Mark × to leave a note that the cell is excluded. Use the same tool on the same cell again to remove that mark. A fixed cat has a small dot and cannot be removed. Use Undo to reverse an ordinary move.
Start with the fixed cats and mark the cells they rule out. Look for a row, column or region that has only one candidate left. The board below is an original GridMew puzzle, not a screenshot from another game. Its worked step names actual coordinates so you can check the reasoning.
Finish without guessing
A conflict message explains a direct row, column, region or touching error. Having no direct conflict does not prove that a guessed placement can lead to a solution. If you are stuck, ask for a hint: first find where to look, then read the explanation, and only apply it when ready.
A win is recorded only when the board itself satisfies all four rules. Your progress and hint use are stored in this browser. Size describes the number of cells; it does not determine difficulty.
Apply the idea to gm-5-0004
r2c3 means row 2, column 3, counting from the top left.
Use gm-5-0004 to make the checks concrete. The fixed cats occupy r1c3, r2c1 and r3c4. That completes rows 1–3 and columns 3, 1 and 4. In row 4, the unused columns alone are not enough: check the occupied regions and the neighbors of r3c4 as well.
The remaining cell is r4c2. Once you place it, update the whole of column 2 before looking at row 5. A single placement has several consequences; counting cats only inside colored regions misses some of them.
A real step from gm-5-0004
row 4 has only one remaining candidate: row 4, column 2. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Check your understanding
Could you place the next cat at r4c3 because it is below the three completed rows?
Show the explanation
No. Column 3 already contains the fixed cat at r1c3, and r4c3 also touches r3c4. A different row does not undo either conflict.