QED Logic quod erat demonstrandum
Logic Ascent

How to solve this 6×6 logic puzzle

6×6 · gentle · 11 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 772). 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 F, so its marker has to land there; that clears every other open cell in the column.
  2. Next, place a marker at E1. Region has exactly one open cell left. Placing here clears the rest of row 1, column E, and its region. Placing here also clears its 1 touching neighbour.
  3. Then, every open cell left in this region sits in row 2, so its marker has to land there; that clears every other open cell in the row.
  4. After that, every open cell left in this region sits in row 3, so its marker has to land there; that clears every other open cell in the row.
  5. Now, every open cell in column D 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.
  6. From there, every remaining candidate in this region touches A3 and B3, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
  7. Following that, place a marker at C3. Region has exactly one open cell left. Placing here clears the rest of row 3, column C, and its region. Placing here also clears its 3 touching neighbours.
  8. First, place a marker at A2. Region has exactly one open cell left. Placing here clears the rest of row 2, column A, and its region.
  9. Next, place a marker at B5. Region has exactly one open cell left. Placing here clears the rest of row 5, column B, and its region.
  10. Then, place a marker at D6. Region has exactly one open cell left. Placing here clears the rest of row 6, column D, and its region.
  11. Finally, place a marker at F4. Region has exactly one open cell left.

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