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 782). Solving it from scratch takes 18 logical steps, using 5 techniques: Single cell, Row/column exclusion, Adjacency clear, Region 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 B, so its marker has to land there; that clears every other open cell in the column.
  2. Next, place a marker at A1. Region has exactly one open cell left. Placing here clears the rest of row 1, column A, and its region.
  3. Then, 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.
  4. After that, every open cell left in this region sits in column D, so its marker has to land there; that clears every other open cell in the column.
  5. Now, every remaining candidate in this region touches E2 and C3 and E3, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
  6. From there, every remaining candidate in this region touches B4 and B5, 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 B6. Region 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.
  8. First, place a marker at C4. Region has exactly one open cell left. Placing here clears the rest of row 4, column C, and its region. Placing here also clears its 1 touching neighbour.
  9. Next, place a marker at D2. Region has exactly one open cell left. Placing here clears the rest of row 2, column D, and its region.
  10. Then, place a marker at F3. Region has exactly one open cell left. Placing here clears the rest of row 3, column F, and its region.
  11. Finally, place a marker at E5. Region has exactly one open cell left.

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