A Medium 8×8 Puzzle Solved with Shape Squeeze in 16 Steps

This 8×8 board rates as medium (difficulty score 839). Solving it from scratch takes 16 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 H, so its marker has to land there; that clears every other open cell in the column.
2. Next, place a marker at G1. Region has exactly one open cell left. Placing here clears the rest of row 1, column G, and its region. Placing here also clears its 1 touching neighbour.
3. Then, every open cell left in this region sits in row 8, so its marker has to land there; that clears every other open cell in the row.
4. After that, together, two regions have open cells only in columns F and E; 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.
5. Now, 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.
6. From there, place a marker at F5. Region has exactly one open cell left. Placing here clears the rest of row 5, column F, and its region.
7. Following that, place a marker at E8. Region has exactly one open cell left. Placing here also clears its 1 touching neighbour.
8. First, 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.
9. Next, every remaining candidate in this region touches C3, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
10. Then, every remaining candidate in this region touches A3, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
11. 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.
12. Now, every remaining candidate in this region touches B3, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
13. From there, place a marker at D3. Row 3 has exactly one open cell left. Placing here clears the rest of row 3, column D, and its region. Placing here also clears its 1 touching neighbour.
14. 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.
15. First, place a marker at B2. Region has exactly one open cell left. Placing here clears the rest of row 2, column B, and its region.
16. Finally, place a marker at C6. Region has exactly one open cell left.

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