A Steady 8×8 Puzzle Solved with Shape Squeeze in 23 Steps

This 8×8 board rates as steady (difficulty score 805). Solving it from scratch takes 23 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 column A, so its marker has to land there; that clears every other open cell in the column.
2. Next, place a marker at B7. Region has exactly one open cell left. Placing here clears the rest of row 7, 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 E, so its marker has to land there; that clears every other open cell in the column.
4. After that, 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.
5. Now, 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.
6. From there, every open cell in column G 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.
7. Following that, every remaining candidate in this region touches F2 and F3, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
8. First, 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.
9. Next, every remaining candidate in this region touches G5 and G6, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
10. Then, place a marker at H6. Row 6 has exactly one open cell left. Placing here clears the rest of row 6, column H, and its region.
11. After that, place a marker at C5. Row 5 has exactly one open cell left. Placing here clears the rest of row 5, column C, and its region.
12. Now, place a marker at F1. Region has exactly one open cell left. Placing here also clears its 2 touching neighbours.
13. From there, place a marker at E3. Region has exactly one open cell left. Placing here clears the rest of row 3, column E, and its region.
14. Following that, place a marker at G4. Region has exactly one open cell left. Placing here clears the rest of row 4, column G, and its region.
15. Finally, place a marker at A2. Region has exactly one open cell left.

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