A Medium 6×6 Puzzle Solved with Shape Squeeze in 13 Steps

This 6×6 board rates as medium (difficulty score 808). Solving it from scratch takes 13 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 A, 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 B, so its marker has to land there; that clears every other open cell in the column.
3. Then, together, two regions have open cells only in rows 1 and 2; 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.
4. After that, place a marker at B3. Region has exactly one open cell left. Placing here clears the rest of row 3, column B, and its region. Placing here also clears its 3 touching neighbours.
5. Now, 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.
6. From there, every open cell in column C 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.
7. Following that, every remaining candidate in this region touches D5 and D6, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
8. First, place a marker at D2. Column 4 has exactly one open cell left. Placing here clears the rest of row 2, column D, and its region.
9. 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.
10. Then, every remaining candidate in this region touches F4 and F5, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
11. After that, place a marker at F6. Region has exactly one open cell left. Placing here clears the rest of row 6, column F, and its region. Placing here also clears its 1 touching neighbour.
12. Now, place a marker at E4. Region has exactly one open cell left.
13. Finally, place a marker at C5. Region has exactly one open cell left.

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