Catdoku is a single-player, Sudoku-style logic puzzle about placing cats on a colored grid. You do not fill every square. Instead, you find the small set of squares where all four placement rules can be true at the same time.
Place exactly one cat in each row, one in each column, and one in each colored region. Cats cannot touch one another.
Four checks decide every move
- Rows: every horizontal row must contain exactly one cat.
- Columns: every vertical column must contain exactly one cat.
- Colored regions: every marked color area must contain exactly one cat.
- No touching: two cats cannot occupy neighboring squares, including squares that meet at a corner.
A square is available only if placing a cat there keeps all four rules possible. The row, column, and region checks control the total number of cats. The no-touch rule removes close neighbors that the first three checks may not eliminate.
Play Catdoku onlineFree in your browser—no account or separate download required. →How to check one placement
Choose a square you are considering and inspect it in the same order every time:
- Look across its row. If that row already has a cat, the square is out.
- Look down its column. If that column already has a cat, eliminate it.
- Look around its colored region. If the region already has a cat, eliminate it.
- Check the neighboring squares. If the new cat would touch another cat, eliminate it.
Passing those checks makes the square possible, but not always certain. Place the cat when every other square for the same row, column, or region has been ruled out. In the shipped game, tap to highlight a square, then double-tap the highlighted square to place your cat.
Find groups with only one square left
The simplest forced move appears when a row, column, or colored region has only one legal square remaining.
Start with a group that already has many impossible squares. Remove any square whose row, column, or region already contains a cat. Then remove squares touching a placed cat. If only one square survives, that is where the group’s cat must go.
After placing it, immediately rescan the connected row, column, region, and neighboring squares. One cat can remove several candidates at once and reveal the next forced move.
You do not need to work from the top-left corner across the board. Jump to whichever row, column, or colored region has the fewest possibilities.
Use colored regions to narrow rows and columns
A region may still have several possible squares, yet all of those squares may lie in the same row. That tells you the row’s cat must be somewhere inside that region, so every square outside the region on that row can be eliminated.
The same idea works with columns. If all remaining positions for a region’s cat fall in one column, remove the other candidates in that column outside the region.
You can also reason in the opposite direction. If a row’s remaining legal squares all sit inside one colored region, that region’s cat must use one of those squares. Other squares in the region can no longer contain a cat.
Use the no-touch rule, especially on diagonals
The one-per-row rule already stops cats from sitting directly beside each other horizontally. The one-per-column rule does the same vertically. That makes corner-to-corner contact the easy detail to miss.
Whenever you place a cat, eliminate the squares immediately around it. The diagonal exclusions often combine with a colored-region boundary to leave another row or region with only one possible square.
Do this check early, not only at the end. A placement that satisfies its row, column, and region can still be illegal if it touches a cat diagonally.
Common Catdoku mistakes
Trying to fill every square
Catdoku is a placement puzzle, not a symbol-filling grid. Most squares remain empty. Your goal is the correct position of one cat per row, column, and colored region.
Checking only three constraints
A square can be unique in its row, column, and region but still touch another cat. Always include the neighboring-square check.
Treating a possible square as a forced square
“A cat can go here” is weaker than “the cat has no other legal square in the group.” Keep scanning until alternatives are eliminated.
Ignoring what a region tells the whole row
Even when a colored region has more than one candidate, the candidates may all occupy one row or column. Use that overlap to remove possibilities elsewhere.
Guessing when one area feels stuck
Move to a different row, column, or region. A forced placement elsewhere may eliminate the candidate that is keeping the difficult area ambiguous.
Questions about Catdoku
What are the rules of Catdoku?
Place exactly one cat in every row, exactly one in every column, and exactly one in every colored region. Cats cannot touch, including corner to corner.
How do I place a cat in Catdoku?
Tap a square to highlight it, then double-tap the highlighted square to place your cat. Before placing it, check the square’s row, column, colored region, and neighboring squares.
Is Catdoku a Sudoku puzzle?
Catdoku is a Sudoku-style logic puzzle with a queens-style placement goal. It uses rows, columns, and colored regions, but you place one cat in each instead of filling every square with different symbols.