A Medium 6×6 Puzzle Solved with Shape Squeeze in 15 Steps

This 6×6 board rates as medium (difficulty score 845). Solving it from scratch takes 15 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, every open cell in column F 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.
3. Then, every remaining candidate in this region touches B1 and B2, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
4. After that, every remaining candidate in this region touches C4, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
5. Now, 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.
6. From there, 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.
7. Following that, every open cell in column E 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.
8. First, every remaining candidate in this region touches F2 and D3 and F3, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
9. Next, every remaining candidate in this region touches B4 and B6 and C6, 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 D6. Region has exactly one open cell left. Placing here clears the rest of row 6, column D, and its region. Placing here also clears its 1 touching neighbour.
11. After that, place a marker at B5. Region has exactly one open cell left. Placing here clears the rest of row 5, column B, and its region.
12. Now, place a marker at C3. Region has exactly one open cell left. Placing here clears the rest of row 3, column C, and its region.
13. From there, place a marker at E2. Region has exactly one open cell left. Placing here clears the rest of row 2, column E, and its region. Placing here also clears its 1 touching neighbour.
14. Following that, place a marker at A1. Region has exactly one open cell left.
15. Finally, place a marker at F4. Region has exactly one open cell left.

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