GridMew

Build your board. Find the next step.

Create your own cat placement puzzle, check it, and get a hint or solution.

A relaxed cat stretching next to a plant
✎ Draw a board▧ Use a screenshot
  1. 1. Set size
  2. 2. Draw regions
  3. 3. Add marks
  4. 4. Check & solve

Choose a region and click cells to paint. Arrow keys move focus, Space uses the selected tool, X marks a cell. Each region must be connected.

What the solver can tell you

It distinguishes an invalid board, no solution, more than one solution, a unique solution, and a search that has not finished. A unique answer stays hidden until you choose to reveal it. A hint is offered only when a supported logical rule explains a step.

Screenshot support

Best results come from upright, evenly spaced square grids with flat, visibly different region colors. Choose the grid size, crop tightly to the board and check the prefilled regions. Similar colors, heavy markings, shadows or missing edges can confuse sampling. Edit regions and marks manually before solving. No particular third-party app or screenshot style is guaranteed.

Solver troubleshooting · Our one-cat rules

How to check a board without losing the reasoning

Use the editor for the one-cat rule set: one cat in each row, column and connected region, with no edge or corner contact. A two-star puzzle or a classic eight-queens board needs different constraints. Check this before copying a board that happens to look similar.

  1. Copy the structure. Choose the size, then paint exactly that many connected regions. A corner-only connection does not join two patches. Region letters identify groups; matching the original color names is unnecessary.
  2. Copy the facts. Add fixed cats separately from your own guesses. Leaving out a fixed cat can turn a unique puzzle into a multiple-solution input.
  3. Check without notes first. Leave Treat × notes as exclusions off to test the regions and cats. Turn it on only to test the additional assumptions in your marks.
  4. Read the result before revealing an answer. Two found arrangements prove ambiguity; one found arrangement proves uniqueness only when the search has finished. A supported hint explains a deduction rather than simply exposing a search answer.

A repeatable notes check

At 6×6, Load an original example loads gm-6-0001 with its fixed cat. Solve it with notes ignored to check the original input. Then use Mark × across every cell in row 1 and enable Treat × notes as exclusions. That deliberately contradictory input has no solution, because row 1 still needs a cat. Turning notes off tests the original board again. The change in result diagnoses the notes; it does not mean the original puzzle changed.

To explore ambiguity, draw six vertical regions on an otherwise empty 6×6 board, one region per column, with no cats or excluded notes. The regional quotas then repeat the column quotas, and more than one arrangement satisfies the remaining rules. Inspect the two examples to see that a connected input is not automatically a unique puzzle.

Diagnose a wrong cat or × · How original puzzle uniqueness is checked