A Medium 11×11 Puzzle Solved with Shape Squeeze in 20 Steps

This 11×11 board rates as medium (difficulty score 825). Solving it from scratch takes 20 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 row 1, so its marker has to land there; that clears every other open cell in the row.
2. Next, 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.
3. Then, 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.
4. After that, every open cell left in this region sits in row 4, so its marker has to land there; that clears every other open cell in the row.
5. Now, every open cell left in this region sits in column G, so its marker has to land there; that clears every other open cell in the column.
6. From there, together, two regions have open cells only in rows 5 and 6; 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.
7. Following that, place a marker at J7. Region has exactly one open cell left. Placing here clears the rest of row 7, column J, and its region. Placing here also clears its 2 touching neighbours.
8. First, place a marker at H4. Region has exactly one open cell left. Placing here clears the rest of row 4, column H, and its region. Placing here also clears its 1 touching neighbour.
9. Next, place a marker at I1. Region has exactly one open cell left. Placing here clears the rest of row 1, column I, and its region.
10. Then, place a marker at G6. Region has exactly one open cell left. Placing here clears the rest of row 6, column G, and its region.
11. After that, place a marker at K9. Region has exactly one open cell left. Placing here clears the rest of row 9, column K, and its region.
12. Now, 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.
13. From there, every open cell in row 11 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.
14. Following that, every remaining candidate in this region touches D3, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
15. First, 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 1 touching neighbour.
16. Next, place a marker at E2. Region has exactly one open cell left. Placing here clears the rest of row 2, column E, and its region.
17. Then, 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.
18. After that, place a marker at A8. Region has exactly one open cell left. Placing here clears the rest of row 8, column A, and its region.
19. Now, place a marker at F10. Region has exactly one open cell left.
20. Finally, place a marker at D11. Region has exactly one open cell left.

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