1. No-Touch Diagonal Elimination
Once a Cat is confirmed, exclude its surrounding eight cells, including the four diagonal neighbors. Also exclude every other cell in its row, column and colored region. At the edge of a board, only neighbors inside the board count. The diagonal restriction applies to adjacent cells, not an entire diagonal.
For example, a Cat at row 3, column 3 excludes the diagonal cells at row 2, columns 2 and 4, and row 4, columns 2 and 4. Row 1, column 1 is not excluded by adjacency alone; another rule may still exclude it.
2. Color Region Row and Column Locking
If an unsatisfied region has at least one candidate and all its remaining candidates lie in one row, its Cat must occupy that row. Exclude cells in other regions on the same row. Apply the same reasoning to a column. Only use candidates left after justified exclusions: an unsupported X can create a false lock.
For example, if a region can only place its Cat at row 4, column 2 or row 4, column 5, every row 4 cell outside that region is excluded. Neither candidate is confirmed yet. This is a manual solving technique; the current hint tool does not provide a dedicated region-locking hint.
3. Use a Checked Contradiction
When direct deductions stop, test one hypothetical Cat or X, then follow only forced moves. The Solver can test one hypothetical Cat or X using limited rule propagation. Reject the assumption only when it produces an explicit contradiction, such as two Cats in one row or an unsatisfied region with no candidates. No contradiction found does not prove the assumption correct.
For example, if a trial Cat removes the last candidate from another unsatisfied region, the trial is impossible. Restore the earlier marks and exclude that trial cell. If the trial merely reaches another undecided position, leave it undecided. A final answer found by search is separate from a rule-based deduction.
4. Use Marks, Hints and Undo Clearly
On Play, level guides and the teaching board, click or tap to cycle empty → X → Cat → empty. Each activation is one move: Undo restores a Cat to X, then X to empty. Enter or Space also cycles; Shift+Enter places or removes a Cat. Fixed starting clues cannot be edited, and X records a cell you have ruled out.
In Play, a top-right assist dot indicates a cell blocked by a Cat in its row or column; it is not an X. A small bottom-right Cat or X is a hint preview, not your move, and does not change progress. For example, two clicks place a Cat and one Undo returns it to X. The Solver instead uses separate tools for regions, fixed clues and current marks.
5. Repeat Elimination Before Guessing
After every confirmed Cat, eliminate blocked cells again and check each unsatisfied region, row and column for a single candidate. For example, if justified exclusions leave one candidate in a region, confirm its Cat, then repeat the checks. Try a checked contradiction only after direct moves stop. If no supported deduction is available, use the Solver rather than turning a guess into a claimed fact.
Reference boards can differ from your board even with the same level number. Compare regions and starting clues before following a guide. Rotation and mirroring align the same board in a different direction; they cannot reconcile different boards. Enter your actual board in the Solver, which distinguishes rule-based hints from a searched answer and may not explain every move.