Cat logic puzzle beginner strategy: mark, scan, place

Start by marking cells ruled out by confirmed cats, then scan each row, column and colour region for a single remaining position. After every placement, update all affected constraints before searching for a harder deduction.

Keep the board's meaning clear

An empty unmarked cell is a possible cat position unless a rule rules it out. An X means you have a reason that the cell is impossible. A cat means the location has been established. Keeping those meanings separate is the foundation of a reliable solve.

Do not cross out a cell simply because another candidate looks more attractive. Later, a row with one unmarked cell will look forced even if the other positions were removed without justification. Good bookkeeping protects the reasoning that follows it.

Begin with confirmed information

For every confirmed cat, exclude the rest of its row, the rest of its column and the rest of its colour region. Then check touching neighbours, especially diagonals. Some cells will already be excluded by more than one rule; that overlap is normal.

Use the same order each time so that no type of exclusion is skipped. The colour region may extend far away from the cat, while a diagonal neighbour may belong to a completely different region. Both still need attention. Do not limit the update to the visually closest cells.

Count candidates in a complete unit

A unit here means a row, a column or a colour region, each requiring one cat. If an unfilled unit has only one legal cell left, that cell must contain its cat. This is the simplest placement pattern and a useful first scan after every update.

For example, suppose column B has several cells crossed out, another touches a confirmed cat diagonally, and only row D remains available. The cat for column B must be at that remaining intersection. The conclusion comes from covering the whole column, not from the cell looking isolated.

Let regions constrain rows before placing

A region may have multiple possible cells but all of them can lie in the same row. Its cat must then occupy that row somewhere inside the region. Cross out the other cells in that row outside the region, while preserving every still-possible cell inside it.

This is useful when no single is immediately visible. You have learned something definite without choosing the exact cat position. The same reasoning works for a region confined to one column, and it can produce a single in another unit after the exclusions are recorded.

A compact solving routine

1. Update exclusions from every confirmed cat.
2. Scan unfilled rows for a sole candidate.
3. Repeat for columns and complete colour regions.
4. Look for a region confined to one row or column.
5. Apply one deduction and restart the simple scan.

Restarting matters because a modest exclusion may create an easy placement. Beginners sometimes continue searching for something clever after the board has already supplied a single. Inspect the changed row, column and region first before widening the search again.

Use diagonal checks deliberately

Imagine a confirmed cat at row B, column C. A candidate at row C, column D is excluded because it touches that cat at a corner. It does not matter that the candidate is in another row, column and region. The contact condition is independent.

When comparing candidates, ask whether all of them share a touching neighbour. If every possible location for a required cat would touch a particular cell, that cell cannot contain another cat. You do not need to decide which candidate is correct to make that exclusion.

Slow down at a blank-looking contradiction

If a unit has no remaining candidate, do not place a cat outside the rules to keep going. Revisit the most recent exclusions and placements. An unjustified X or a missed diagonal restriction can distort the next steps. Find the first unsupported action rather than building on the contradiction.

A hint is useful when you have completed the routine and cannot identify another justified change. Read its explanation, find the relevant unit and reproduce the exclusion yourself. The goal is to add a recognisable pattern to your next scan.

Where to play

哈基米数独 (Hachimi) offers this cat-region puzzle on HarmonyOS. Tap to mark an X, double-tap to place a cat, and drag to mark several cells. Wrong placements cost lives, so a mark-first routine helps you learn without using guesses as tests.