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

This 11×11 board rates as steady (difficulty score 837). Solving it from scratch takes 20 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 column K, 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 J, 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 columns H and I; 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.
4. After that, place a marker at G11. Region has exactly one open cell left. Placing here clears the rest of row 11, column G, and its region. Placing here also clears its 1 touching neighbour.
5. 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.
6. From there, place a marker at J9. Region has exactly one open cell left. Placing here clears the rest of row 9, column J, and its region.
7. Following that, place a marker at F8. Region has exactly one open cell left. Placing here clears the rest of row 8, column F, and its region. Placing here also clears its 1 touching neighbour.
8. First, 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.
9. Next, every open cell left in this region sits in column I, so its marker has to land there; that clears every other open cell in the column.
10. Then, 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.
11. After that, 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. Placing here also clears its 3 touching neighbours.
12. Now, place a marker at B10. Region has exactly one open cell left. Placing here clears the rest of row 10, column B, and its region.
13. From there, place a marker at A1. Row 1 has exactly one open cell left. Placing here clears the rest of row 1, column A, and its region.
14. Following that, place a marker at C7. Region has exactly one open cell left. Placing here clears the rest of row 7, column C, and its region.
15. First, every remaining candidate in this region touches H4, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
16. Next, every remaining candidate in this region touches I5, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
17. Then, place a marker at H5. Row 5 has exactly one open cell left. Placing here clears the rest of row 5, column H, and its region. Placing here also clears its 1 touching neighbour.
18. After that, place a marker at I3. Region has exactly one open cell left. Placing here clears the rest of row 3, column I, and its region.
19. Now, place a marker at K4. Region has exactly one open cell left. Placing here clears the rest of row 4, column K, and its region.
20. Finally, place a marker at E6. Region has exactly one open cell left.

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