Finish every consequence
After placing a cat, mark its row, its column, its region, and every adjacent cell. One missing mark can hide the next certain move, and a board that looks impossible is usually a board with an unfinished sweep somewhere behind you.
When you are stuck, do not look for something new first. Go back to the last two or three cats you placed and re-trace their consequences. The missing deduction is there more often than not.
Lock regions onto lines
If every remaining cell in a region lies on one row, that region’s cat must occupy that row — even though you cannot yet say which cell. Every other cell in that row therefore becomes impossible, including cells in completely different regions.
This is the highest-value pattern in the game, and it costs nothing to check. After each placement, glance at the small regions and ask whether their survivors have collapsed onto a single line.
And lock lines onto regions
The same argument runs backwards. If every remaining candidate in a row sits inside one region, then that region’s cat is the row’s cat. Every other cell of that region — anywhere else on the board — can be eliminated. Players who only read the pattern in one direction leave half its value on the table.
Compare candidate sets
If two rows are limited to the same two columns, those columns are reserved for that pair. This often unlocks a third row without ever deciding which of the two cats goes where.
The pattern scales. Three rows confined to the same three columns reserve all three, and the same reasoning applies to columns confined to rows. You are not identifying cats — you are identifying territory that is already spoken for.
Count what is left
Late in a board, stop scanning and start counting. Cats remaining, rows remaining, columns remaining, and regions remaining are all the same number, and matching them against each other collapses positions that look wide open. If three cats remain but only three regions are unresolved, each of those regions takes exactly one, and any cell of theirs that cannot serve is finished.
Mind the geometry of edges
The no-touch rule is weaker at the border. A cat in the middle of the board forbids eight neighbors; a cat in a corner forbids three. Regions that hug an edge are therefore looser than their size suggests, and central regions are tighter. When two candidate placements look equally plausible, the one nearer the middle usually rules out more and is worth testing first.
Use contradiction sparingly
On expert boards, assume one candidate holds a cat and follow only certain consequences. If the assumption produces a conflict, you can safely eliminate that candidate. The full replay labels this technique honestly as bounded contradiction.
Keep the chain short and keep it certain. A contradiction you followed for three forced moves is a proof. A contradiction you followed for fifteen speculative moves is a guess wearing a proof’s clothing, and it is how solvable boards get abandoned.
Mistakes worth knowing
Three errors account for most stuck boards: forgetting the diagonal neighbors when sweeping a placed cat, treating two corner-touching blocks of the same color as one region, and marking a cell impossible for a reason you never actually verified. The first two are mechanical. The third is the dangerous one, because a single unjustified paw makes the rest of the board lie to you.