GridMew1Check region B
region B 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 1. Place one cat, then exclude 7 other cells.Puzzle gm-8-0008
8 × 8 challenge
Take this puzzle one clear step at a time.
Try the puzzle yourself, then explore how the deductions build.
Puzzle board · starting state
Your starting point
This original 8×8 board has 8 connected regions and 2 fixed cats. The smallest region is B, with 4 cells. Start by ruling out every other cell in each fixed cat’s row, column and region, plus its immediate neighbors.
The verified route below uses 6 forced placements and 3 candidate-elimination steps after the givens. Region sizes: A: 6 · B: 4 · C: 13 · D: 21 · E: 5 · F: 6 · G: 5 · H: 4. These are observations about this board, not a guarantee that a smaller region always contains the next move.
Read each diagram in sequence. Cats and × marks in the before-state come from earlier deductions. Green outlines identify the current observation. Open the final answer only when you want the spoiler.
Step-by-step walkthrough
2Use a candidate lock
Every candidate in row 3 lies in region C (row 3, column 4; row 3, column 6; row 3, column 7; row 3, column 8). Its cat must use that shared section. Exclude row 4, column 4; row 4, column 6; row 4, column 7; row 4, column 8 from the rest of region C.
Before step 2. Exclude 4 cells; then scan for a new single.3Check row 4
row 4 has only one remaining candidate: row 4, column 3. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 3. Place one cat, then exclude 6 other cells.4Check column 4
column 4 has only one remaining candidate: row 8, column 4. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 4. Place one cat, then exclude 3 other cells.5Use a candidate lock
Every candidate in row 6 lies in region F (row 6, column 6; row 6, column 7; row 6, column 8). Its cat must use that shared section. Exclude row 7, column 8 from the rest of region F.
Before step 5. Exclude 1 cells; then scan for a new single.6Exclude common neighbors
The cat in row 6 must occupy one of row 6, column 6; row 6, column 7; row 6, column 8. Each of row 7, column 7 touches every candidate, so none can hold a cat.
Before step 6. Exclude 1 cells; then scan for a new single.7Check row 7
row 7 has only one remaining candidate: row 7, column 6. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 7. Place one cat, then exclude 3 other cells.8Check row 6
row 6 has only one remaining candidate: row 6, column 8. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 8. Place one cat, then exclude 1 other cells.9Check row 3
row 3 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 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: r1c5, r2c2, r3c7, r4c3, r5c1, r6c8, r7c6, r8c4.