QED Logic quod erat demonstrandum
Logic Ascent

How to solve this 6×6 logic puzzle

6×6 · gentle · 12 steps

A
B
C
D
E
F
1
2
3
4
5
6
1
2
🐱
3🐱
4
🐱
5
🐱
6
🐱
🐱

This 6×6 board rates as gentle (difficulty score 784). Solving it from scratch takes 18 logical steps, using 6 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement, Line confinement, Shape squeeze. Every step below is forced: nothing here is a guess.

  1. First, every open cell left in this region sits in column C, so its marker has to land there; that clears every other open cell in the column.
  2. Next, every open cell left in this region sits in row 6, so its marker has to land there; that clears every other open cell in the row.
  3. Then, every open cell in column A belongs to the same region, so that region's marker has to be somewhere in this column; that clears every other open cell in the region.
  4. After that, place a marker at B6. Column 2 has exactly one open cell left. Placing here clears the rest of row 6, column B, and its region. Placing here also clears its 1 touching neighbour.
  5. Now, every open cell in row 5 belongs to the same region, so that region's marker has to be somewhere in this row; that clears every other open cell in the region.
  6. From there, place a marker at A4. Row 4 has exactly one open cell left. Placing here clears the rest of row 4, column A, and its region.
  7. Following that, every open cell in row 1 belongs to the same region, so that region's marker has to be somewhere in this row; that clears every other open cell in the region.
  8. First, every remaining candidate in this region touches D2 and D3, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
  9. Next, place a marker at E3. Region has exactly one open cell left. Placing here clears the rest of row 3, column E, and its region.
  10. Then, place a marker at C2. Region has exactly one open cell left. Placing here also clears its 1 touching neighbour.
  11. After that, place a marker at F1. Region has exactly one open cell left. Placing here clears the rest of row 1, column F, and its region.
  12. Finally, place a marker at D5. Region has exactly one open cell left.

The key move here was Shape squeeze. Once you can spot that, this board falls quickly. ∎