Original puzzle gm-6-0019
By GridMew · Published 15 October 2026 · Updated 16 October 2026
6 × 6 challenge
Read the starting position, follow the deductions, and check the move that is easy to misread.
Coordinates such as r2c3 mean row 2, column 3. Count rows from the top and columns from the left.
Column 3’s candidates are r2c3 and r6c3, separated by several rows. Both lie in B. Their distance does not weaken the reservation: the required column cat must satisfy B.
6×6 · 2 fixed cats · 5 explained deductions. Region sizes: A: 3 · B: 16 · C: 6 · D: 2 · E: 5 · F: 4.
The lock excludes B’s r2c5 and r3c2. Row 3 then resolves at r3c6, whose column effect helps settle row 2.
r3c2 need not touch both column candidates. This is a shared-region quota argument, not a common-neighbor rule.
Green marks the cell being discussed, not a cat to place. This is the position before step 1; compare the deduction below.
Each line is one row, left to right. Matching letters belong to the same connected region.
A A B B B B A B B B B C B B B B C C B E B D C C E E B D F C E E B F F F
Fixed cats: row 1, column 1; row 4, column 4. One cat is required in each row, column and region.
Every candidate in column 3 lies in region B (row 2, column 3; row 6, column 3). Its cat must use that shared section. Exclude row 2, column 5; row 3, column 2 from the rest of region B.
Before step 1. Exclude 2 cells; then scan for a new single.row 3 has only one remaining candidate: row 3, column 6. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 2. Place one cat, then exclude 3 other cells.row 2 has only one remaining candidate: row 2, column 3. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 3. Place one cat, then exclude 1 other cells.row 5 has only one remaining candidate: row 5, column 2. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 4. Place one cat, then exclude 1 other cells.row 6 has only one remaining candidate: row 6, column 5. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 5. Place one cat, then exclude 0 other cells.The final cats satisfy every row, column and region quota, with no edge or corner contact.
Cat positions: r1c1, r2c3, r3c6, r4c4, r5c2, r6c5.
gm-6-0015 · 6×6 · challenge
Practice candidate locks on another 6×6 board.
Read this walkthrough →gm-8-0002 · 8×8 · challenge
Transfer candidate locks to a 8×8 grid; compare how the candidates change.
Read this walkthrough →gm-6-0007 · 6×6 · challenge
Compare this route with shared-neighbor exclusions, and check why that different rule is needed.
Read this walkthrough →
GridMew