A Medium 6×6 Puzzle Solved with Shape Squeeze in 14 Steps

This 6×6 board rates as medium (difficulty score 831). Solving it from scratch takes 14 logical steps, using 7 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement, Line confinement, Paired regions, 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, every open cell left in this region sits in column E, so its marker has to land there; that clears every other open cell in the column.
3. Then, 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.
4. After that, every open cell in row 6 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.
5. Now, every remaining candidate in this region touches C3, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
6. From there, every remaining candidate in this region touches E4 and E5, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
7. Following that, together, two regions have open cells only in rows 2 and 3; with one marker each, those two markers have to fill exactly those two rows, so every other region's open cells there can be cleared.
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 C2. Region has exactly one open cell left. Placing here clears the rest of row 2, column C, and its region. Placing here also clears its 2 touching neighbours.
10. Then, 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.
11. After that, place a marker at E3. Region has exactly one open cell left. Placing here also clears its 2 touching neighbours.
12. Now, place a marker at F5. Region has exactly one open cell left. Placing here clears the rest of row 5, column F, and its region.
13. From there, place a marker at B4. Region has exactly one open cell left. Placing here clears the rest of row 4, column B, and its region.
14. Finally, place a marker at D6. Region has exactly one open cell left.

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