GridMew1Check region E
region E has only one remaining candidate: row 5, column 4. 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-8-0001
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 3 fixed cats. The smallest region is E, with 1 cell. 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 5 forced placements and 2 candidate-elimination steps after the givens. Region sizes: A: 8 · B: 7 · C: 9 · D: 10 · E: 1 · F: 4 · G: 20 · H: 5. 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
2Check column 1
column 1 has only one remaining candidate: row 6, column 1. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 2. Place one cat, then exclude 1 other cells.3Use a candidate lock
Every candidate in row 1 lies in region A (row 1, column 5; row 1, column 6; row 1, column 8). Its cat must use that shared section. Exclude row 2, column 8 from the rest of region A.
Before step 3. Exclude 1 cells; then scan for a new single.4Exclude common neighbors
The cat in row 2 must occupy one of row 2, column 5; row 2, column 6. Each of row 1, column 5; row 1, column 6 touches every candidate, so none can hold a cat.
Before step 4. Exclude 2 cells; then scan for a new single.5Check row 1
row 1 has only one remaining candidate: row 1, column 8. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 5. Place one cat, then exclude 1 other cells.6Check row 4
row 4 has only one remaining candidate: row 4, column 6. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 6. Place one cat, then exclude 1 other cells.7Check row 2
row 2 has only one remaining candidate: row 2, column 5. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 7. 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: r1c8, r2c5, r3c2, r4c6, r5c4, r6c1, r7c3, r8c7.