A Medium 11×11 Puzzle Solved with Shape Squeeze in 22 Steps

This 11×11 board rates as medium (difficulty score 874). Solving it from scratch takes 22 logical steps, using 6 techniques: Single cell, Row/column exclusion, Adjacency clear, Region 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 column B, 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 C, so its marker has to land there; that clears every other open cell in the column.
5. Now, 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.
6. From there, every remaining candidate in this region touches I1 and H3 and I3, 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 columns J and K; with one marker each, those two markers have to fill exactly those two columns, so every other region's open cells there can be cleared.
8. First, every remaining candidate in this region touches B10 and D10, 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 B11. Region has exactly one open cell left. Placing here clears the rest of row 11, column B, and its region. Placing here also clears its 2 touching neighbours.
10. Then, place a marker at C9. Region has exactly one open cell left. Placing here clears the rest of row 9, column C, and its region. Placing here also clears its 1 touching neighbour.
11. 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.
12. Now, every open cell left in this region sits in row 10, so its marker has to land there; that clears every other open cell in the row.
13. From there, place a marker at K1. Column 11 has exactly one open cell left. Placing here clears the rest of row 1, column K, and its region.
14. Following that, together, two regions have open cells only in rows 6 and 7; 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.
15. First, place a marker at I5. Region has exactly one open cell left. Placing here clears the rest of row 5, column I, and its region. Placing here also clears its 2 touching neighbours.
16. Next, place a marker at H2. Region has exactly one open cell left. Placing here clears the rest of row 2, column H, and its region. Placing here also clears its 1 touching neighbour.
17. Then, 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.
18. After that, 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.
19. Now, every remaining candidate in this region touches F3, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
20. From there, place a marker at G4. Region has exactly one open cell left. Placing here clears the rest of row 4, column G, and its region.
21. Following that, place a marker at E3. Region has exactly one open cell left. Placing here clears the rest of row 3, column E, and its region.
22. Finally, place a marker at F10. Region has exactly one open cell left.

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