A Medium 9×9 Puzzle Solved with Shape Squeeze in 16 Steps

This 9×9 board rates as medium (difficulty score 807). Solving it from scratch takes 16 logical steps, using 5 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement, Shape squeeze. Every step below is forced: nothing here is a guess.

1. First, 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.
2. Next, every open cell left in this region sits in column H, so its marker has to land there; that clears every other open cell in the column.
3. Then, every remaining candidate in this region touches H2, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
4. After that, place a marker at H3. Region has exactly one open cell left. Placing here clears the rest of row 3, column H, and its region. Placing here also clears its 3 touching neighbours.
5. Now, 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.
6. From there, place a marker at F2. Region has exactly one open cell left. Placing here clears the rest of row 2, column F, and its region.
7. Following that, place a marker at A4. Region has exactly one open cell left. Placing here clears the rest of row 4, column A, and its region. Placing here also clears its 1 touching neighbour.
8. First, every open cell left in this region sits in row 6, 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 row 5, so its marker has to land there; that clears every other open cell in the row.
10. Then, 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.
11. After that, every remaining candidate in this region touches C5 and B7 and C7, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
12. Now, place a marker at E5. Region has exactly one open cell left. Placing here clears the rest of row 5, column E, and its region.
13. From there, place a marker at D7. Row 7 has exactly one open cell left. Placing here clears the rest of row 7, column D, and its region. Placing here also clears its 1 touching neighbour.
14. Following that, place a marker at B6. Region has exactly one open cell left. Placing here clears the rest of row 6, column B, and its region.
15. First, 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.
16. Finally, place a marker at G8. Region has exactly one open cell left.

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