How to solve this 8×8 logic puzzle

8×8 · steady · 14 steps

This 8×8 board rates as steady (difficulty score 693). Solving it from scratch takes 24 logical steps, using 5 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement, Paired regions. Every step below is forced — nothing here is a guess.

First, every open cell left in this region sits in row 1, so its marker has to land there — clearing every other open cell in the row.
Next, together, two regions have open cells only in columns 1 and 2 — 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.
Then, every open cell left in this region sits in column 3, so its marker has to land there — clearing every other open cell in the column.
After that, together, two regions have open cells only in rows 2 and 3 — with one marker each, those two markers have to fill exactly those two rows, so every other region's open cells there can be cleared.
Now, every open cell left in this region sits in row 4, so its marker has to land there — clearing every other open cell in the row.
From there, together, two regions have open cells only in columns 4 and 5 — 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.
Following that, place a marker at row 5, column 6. Region has exactly one open cell left. Placing here clears the rest of row 5, column 6, and its region. Placing here also clears its 2 touching neighbours.
First, place a marker at row 4, column 4. Region has exactly one open cell left. Placing here clears the rest of row 4, column 4, and its region. Placing here also clears its 1 touching neighbour.
Next, place a marker at row 2, column 3. Region has exactly one open cell left. Placing here clears the rest of row 2, column 3, and its region. Placing here also clears its 1 touching neighbour.
Then, place a marker at row 1, column 1. Region has exactly one open cell left. Placing here clears the rest of row 1, column 1, and its region.
After that, place a marker at row 3, column 8. Region has exactly one open cell left. Placing here clears the rest of row 3, column 8, and its region.
Now, place a marker at row 8, column 5. Region has exactly one open cell left. Placing here clears the rest of row 8, column 5, and its region.
From there, place a marker at row 7, column 7. Region has exactly one open cell left. Placing here clears the rest of row 7, column 7, and its region.
Finally, place a marker at row 6, column 2. Region has exactly one open cell left.

The key move here was Paired regions — once you can spot that, this board falls quickly. ∎