GridMew1Check row 8
row 8 has only one remaining candidate: row 8, column 1. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 1. Place one cat, then exclude 5 other cells.Successive column reservations cross the upper half
Original puzzle gm-8-0009
By GridMew · Published 15 October 2026 · Updated 16 October 2026
8 × 8 challenge
Read the starting position, follow the deductions, and check the move that is easy to misread.
Puzzle board · starting state
How to approach this board
Coordinates such as r2c3 mean row 2, column 3. Count rows from the top and columns from the left.
Rows 8 and 5 provide the opening singles at r8c1 and r5c8. With those edges settled, column 2 can be reserved for B and column 4 for D. The placements come after those restrictions.
8×8 · 2 fixed cats · 9 explained deductions. Region sizes: A: 4 · B: 18 · C: 4 · D: 9 · E: 6 · F: 6 · G: 16 · H: 1.
A deduction worth checking
Column 6 is reduced to r1c6 or r2c6. Both touch the two top cells in column 7, so column 7 forces r3c7.
A move to double-check · r3c6
The column-4 reservation excludes r3c6 through region D. Its distance from the column’s two candidates is not relevant to that regional argument.
Green marks the cell being discussed, not a cat to place. This is the position before step 4; compare the deduction below.
Read the starting board as text
Each line is one row, left to right. Matching letters belong to the same connected region.
B B B B A A A A B B B B D C C E B B B D D D C E B B D D D G C E B B F D D G G E B B F G G G G E B F F G G G G E H F F G G G G G
Fixed cats: row 7, column 5; row 6, column 3. One cat is required in each row, column and region.
Step-by-step walkthrough
2Check row 5
row 5 has only one remaining candidate: row 5, column 8. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 2. Place one cat, then exclude 5 other cells.3Use a candidate lock
Every candidate in column 2 lies in region B (row 1, column 2; row 2, column 2; row 3, column 2; row 4, column 2). Its cat must use that shared section. Exclude row 1, column 4; row 2, column 4 from the rest of region B.
Before step 3. Exclude 2 cells; then scan for a new single.4Use a candidate lock
Every candidate in column 4 lies in region D (row 3, column 4; row 4, column 4). Its cat must use that shared section. Exclude row 3, column 6 from the rest of region D.
Before step 4. Exclude 1 cells; then scan for a new single.5Exclude common neighbors
The cat in column 6 must occupy one of row 1, column 6; row 2, column 6. Each of row 1, column 7; row 2, column 7 touches every candidate, so none can hold a cat.
Before step 5. Exclude 2 cells; then scan for a new single.6Check column 7
column 7 has only one remaining candidate: row 3, column 7. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 6. Place one cat, then exclude 3 other cells.7Check row 2
row 2 has only one remaining candidate: row 2, column 2. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 7. Place one cat, then exclude 2 other cells.8Check row 1
row 1 has only one remaining candidate: row 1, column 6. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 8. Place one cat, then exclude 0 other cells.9Check row 4
row 4 has only one remaining candidate: row 4, column 4. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 9. Place one cat, then exclude 0 other cells.Show solution · reveals all cat positions
The final cats satisfy every row, column and region quota, with no edge or corner contact.
Cat positions: r1c6, r2c2, r3c7, r4c4, r5c8, r6c3, r7c5, r8c1.
Try another puzzle
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