A Medium 8×8 Puzzle Solved with Shape Squeeze in 17 Steps

This 8×8 board rates as medium (difficulty score 828). Solving it from scratch takes 17 logical steps, using 6 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement, Line confinement, Shape squeeze. Every step below is forced: nothing here is a guess.

1. 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.
2. Next, place a marker at B3. Region has exactly one open cell left. Placing here clears the rest of row 3, column B, and its region. Placing here also clears its 2 touching neighbours.
3. Then, 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.
4. After that, every open cell in row 1 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.
5. Now, every remaining candidate in this region touches G1 and H1, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
6. From there, every remaining candidate in this region touches E5 and F5, 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 column G, so its marker has to land there; that clears every other open cell in the column.
8. First, place a marker at H2. Region has exactly one open cell left. Placing here clears the rest of row 2, column H, and its region.
9. Next, 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.
10. Then, place a marker at A1. Column 1 has exactly one open cell left. Placing here clears the rest of row 1, column A, and its region.
11. After that, every open cell in column C belongs to the same region, so that region's marker has to be somewhere in this column; that clears every other open cell in the region.
12. Now, every open cell in column D belongs to the same region, so that region's marker has to be somewhere in this column; that clears every other open cell in the region.
13. From there, place a marker at C7. Row 7 has exactly one open cell left. Placing here clears the rest of row 7, column C, and its region. Placing here also clears its 1 touching neighbour.
14. Following that, place a marker at D5. Region has exactly one open cell left. Placing here clears the rest of row 5, column D, and its region. Placing here also clears its 1 touching neighbour.
15. First, place a marker at F4. Region has exactly one open cell left. Placing here clears the rest of row 4, column F, and its region.
16. Next, place a marker at G6. Region has exactly one open cell left.
17. Finally, place a marker at E8. Region has exactly one open cell left.

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