Learn to play Cat Sudoku: place cats, mark excluded squares and use the board tools. Follow the steps, then start your first free puzzle.
Plainoku uses Queens-style placement rules. You are finding one home for each cat, rather than filling a grid with numbers. Start on the 5×5 Easy board: fewer squares make it easier to see how a placement affects its row, column and colored region.
1. Read your Cat Sudoku board before placing cats
Look at the colored areas and their boundary lines. Every row needs one cat, every column needs one cat, and every color region needs one cat. Two cats cannot touch, even at a corner. A five-row board therefore needs five cats, not a cat in every square.
Find a small region first. A region containing just one square tells you exactly where its cat belongs. A longer region may still have several choices. Compare those choices with the surrounding rows and columns before committing. The complete Cat Sudoku rules explain the difference between a move that currently fits and a move that belongs to the final solution.
2. Place a cat and check what changed
With Mark turned off, tap an empty square to place a cat. Tap that cat again to remove it. After placing one, scan its entire row and column, the rest of its color region, and the neighboring squares. Those positions cannot contain another cat while this placement remains.
For example, a cat at row 3, column 3 excludes the other squares in row 3 and column 3. It also excludes row 2, column 2 because those squares touch diagonally. A farther diagonal square is not excluded just for being on the same diagonal; check its color region and other constraints separately.
3. Use Mark to record excluded squares
Press Mark below the board to switch from cats to crosses. Tap a square you have ruled out to add a cross; tap it again in Mark mode to clear the cross. Press Mark again when you are ready to place another cat. The highlighted control shows whether Mark is active.
Crosses are manual notes. The board does not automatically mark every square affected by a cat or decide whether your notes are correct. Marking a square that already contains a cat replaces that cat with a cross, so check the active mode before tapping. Read the exclusion-mark guide for a repeatable way to maintain useful notes.
4. Correct a move with Erase or Undo
Erase clears the selected square, removing its cat or cross. A tap both selects a square and uses the current mode; keyboard focus can select a square without changing its contents. Undo restores the previous cat-and-mark arrangement. Use it soon after an accidental tap or a placement you want to reconsider.
When cats conflict, their squares turn red and the explanation below the controls identifies the broken rule. Remove a conflicting cat, then review any crosses you added because of it. A placement without a red warning can still be a wrong turn: the warning describes current conflicts, rather than promising that every remaining cat will fit.
5. Use Hint when you want answer assistance
Hint first removes an incorrectly placed cat if one is present. Otherwise, it adds one cat at a correct position and clears a cross from that square. You can undo a hint while the puzzle is still in progress.
Hint reveals part of the checked solution; it does not explain a deduction. To keep learning, pause after the hint and inspect the affected row, column, region and neighbors. Try to explain the placement yourself before asking for another. For an independent solving routine, practise scanning the board.
6. Play Cat Sudoku with a keyboard
Tab enters the board at one square. Arrow keys move between squares and stop at the edges. Enter or Space uses the selected square in the active cat or Mark mode; Tab moves out to the surrounding controls. The board does not require a separate Tab press for every square.
N toggles Mark, Z undoes a move, and Delete or Backspace clears the selected square. These shortcuts do not take over while you are using the difficulty selector. Follow the selected square outline and the square's row-and-column label when reviewing a move.
7. Finish, replay or try today's puzzle
Completion is announced automatically when the required cats satisfy all placement rules. You do not need to cross out every unused square. Play again opens a fresh practice puzzle at the same size; check the Mark control before your next tap.
The daily Cat Sudoku is a fixed 6×6 puzzle for your device's local calendar date. Its completion button starts a practice puzzle, which does not extend the daily streak. Repeating the same daily completion does not add another daily result. Your board and statistics stay in this browser when storage is available. You can choose any of the five board sizes immediately; their names describe size, rather than calibrated logical difficulty.
Start your first Cat Sudoku puzzle, or return to the Cat Sudoku rules and guides.