MeowSolverStrategy · step 3 of 6
Confinement & locked sets
You do not need to know where a region’s cat goes to profit from knowing roughly where it must be.
The purple region lives entirely in row 2 — so row 2’s cat is purple, and the yellow and blue squares in that row are dead.
The purple region’s cat has to go somewhere in the purple squares — and every purple square sits in the same row. That row gets exactly one cat, and purple has now claimed it. Every non-purple square in the row is a cross, even though the cat’s exact position is still unknown.
The same logic runs in every direction: a region confined to one column claims that column; and mirrored, a row or column whose survivors are all one color claims that region — so the region’s squares outside the line all die.
Locked pairs and triples
The grown-up version: if two regions only have survivors in the same two rows, those two cats occupy both rows between them — every square of any other color in those rows is a cross. The same holds for three regions in three rows, and for columns. Meowdoku hard levels and late-game Queens boards lean on pairs constantly; triples and quadruples are rarer but MeowSolver checks for them too (they show up as “locked set” hints).
The big block
The same idea scales all the way up, and at the top end it stops looking like a subtle pattern and starts looking like a shape. On a 10×10, if five colors are all packed into the left five columns — no square of any of them reaches column 6 — then those five cats fill columns 1 to 5 between them. Every square of every other color in those five columns is dead, often a dozen or more crosses from a single look.
This one is worth training your eye for, because you spot it by scanning a region of the board rather than by comparing lists of colors: glance at a block of columns (or rows) and ask whether the colors inside it stay inside it. Boards that look impenetrable from the opening position often crack on exactly this — it is usually the first real move, and everything after it is forced moves and tidying.
MeowSolver searches locked sets from the smallest size upward, so you will only ever see a big one when nothing simpler was available.
In double-cat play
At two cats per line the idea only gets stronger. A color confined to one row or column now claims both of that line’s cats — so every other square in the line still dies. And a new bonus appears when the color’s open squares are exactly four consecutive squares:
Purple’s open squares are four consecutive cells of one column. Its two cats claim the whole column — the squares above and below the run die — and wherever the pair lands, every square flanking the run is touched too.
Purple needs two cats among four squares in a line, and cats can’t touch — so the only legal pairs are top-and-third, the two ends, or second-and-bottom: every one of them leaves a cat within a step of all four rows. That means every square beside the run, in both neighboring lines, sits next to a cat no matter how the pair falls. Cross the whole flank, on top of the rest of the column. MeowSolver fires this as a Trapped colour hint — it outlines the trapped color’s squares and marks the line and flank crosses together.
How to spot it without exhaustive search
- Watch regions as they shrink. The moment a region’s survivors fit in one line, fire.
- Long skinny regions are born confined — check them before making any marks at all.
- Scan lines whose survivors look monochrome; that is the mirrored version staring at you.