A Medium 6×6 Puzzle Solved with Forced Chain in 11 Steps

This 6×6 board rates as medium (difficulty score 913). Solving it from scratch takes 11 logical steps, using 6 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement, Shape squeeze, Forced chain. 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 B6. Region has exactly one open cell left. Placing here clears the rest of row 6, column B, and its region. Placing here also clears its 2 touching neighbours.
3. Then, 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.
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 remaining candidate in this region touches D2 and D3, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
6. From there, marking D1 would force C3 (the last open cell in region 1), then F5 (the last open cell in region 4), and then row 2 would be left with no open cell for its marker. So D1 can't be the marker there.
7. Following that, place a marker at D5. Column 4 has exactly one open cell left. Placing here clears the rest of row 5, column D, and its region.
8. First, every remaining candidate in this region touches F1 and F2, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
9. Next, place a marker at F3. Region has exactly one open cell left. Placing here clears the rest of row 3, column F, and its region. Placing here also clears its 1 touching neighbour.
10. Then, place a marker at E1. Region has exactly one open cell left.
11. Finally, place a marker at C2. Region has exactly one open cell left.

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