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

This 8×8 board rates as medium (difficulty score 826). Solving it from scratch takes 16 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, together, two regions have open cells only in columns G and H; 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.
2. Next, every open cell left in this region sits in column F, 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 D 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.
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 in row 4 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.
6. From there, every remaining candidate in this region touches E2 and G2, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
7. Following that, 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.
8. First, every remaining candidate in this region touches E3, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
9. Next, 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.
10. Then, place a marker at F3. Region has exactly one open cell left.
11. After that, place a marker at E8. Region has exactly one open cell left. Placing here clears the rest of row 8, column E, and its region.
12. Now, place a marker at A7. Region has exactly one open cell left. Placing here clears the rest of row 7, column A, and its region.
13. From there, place a marker at B4. Region has exactly one open cell left. Placing here also clears its 1 touching neighbour.
14. Following that, place a marker at C6. Region has exactly one open cell left. Placing here clears the rest of row 6, column C, and its region.
15. First, place a marker at H5. Region has exactly one open cell left. Placing here clears the rest of row 5, column H, and its region.
16. Finally, place a marker at G1. Region has exactly one open cell left.

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