A Medium 10×10 Puzzle Solved with Shape Squeeze in 17 Steps

This 10×10 board rates as medium (difficulty score 805). Solving it from scratch takes 17 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, 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. Placing here also clears its 2 touching neighbours.
3. Then, 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.
4. After that, every open cell left in this region sits in column D, 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 row 1, so its marker has to land there; that clears every other open cell in the row.
6. From there, together, two regions have open cells only in columns E and F; 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.
7. Following that, place a marker at G3. Region has exactly one open cell left. Placing here clears the rest of row 3, column G, and its region. Placing here also clears its 2 touching neighbours.
8. First, every open cell in row 2 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.
9. Next, place a marker at I4. Row 4 has exactly one open cell left. Placing here clears the rest of row 4, column I, and its region.
10. Then, place a marker at J2. Region has exactly one open cell left.
11. After that, place a marker at E6. Row 6 has exactly one open cell left. Placing here clears the rest of row 6, column E, and its region. Placing here also clears its 1 touching neighbour.
12. Now, place a marker at F1. Region has exactly one open cell left.
13. From there, place a marker at H7. Row 7 has exactly one open cell left. Placing here clears the rest of row 7, column H, and its region.
14. Following that, every remaining candidate in this region touches C9, 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 C10. Region has exactly one open cell left. Placing here clears the rest of row 10, column C, and its region. Placing here also clears its 1 touching neighbour.
16. Next, place a marker at D8. Region has exactly one open cell left. Placing here clears the rest of row 8, column D, and its region.
17. Finally, place a marker at A9. Region has exactly one open cell left.

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