QED

How to solve this 8×8 logic puzzle

8×8 · gentle · 10 steps

This 8×8 board rates as gentle (difficulty score 437). Solving it from scratch takes 21 logical steps, using 4 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement. Every step below is forced — nothing here is a guess.

  1. First, place a marker at row 1, column 7. Region has exactly one open cell left. Placing here clears the rest of row 1, column 7, and its region. Placing here also clears its 2 touching neighbours.
  2. Next, place a marker at row 2, column 5. Region has exactly one open cell left. Placing here clears the rest of row 2, column 5, and its region. Placing here also clears its 2 touching neighbours.
  3. Then, every open cell left in this region sits in column 8, so its marker has to land there — clearing every other open cell in the column.
  4. After that, every open cell left in this region sits in column 6, so its marker has to land there — clearing every other open cell in the column.
  5. Now, place a marker at row 5, column 4. Region has exactly one open cell left. Placing here clears the rest of row 5, column 4, and its region. Placing here also clears its 2 touching neighbours.
  6. From there, place a marker at row 7, column 3. Region has exactly one open cell left. Placing here clears the rest of row 7, column 3, and its region. Placing here also clears its 2 touching neighbours.
  7. Following that, place a marker at row 3, column 2. Region has exactly one open cell left. Placing here clears the rest of row 3, column 2, and its region. Placing here also clears its 1 touching neighbour.
  8. First, place a marker at row 4, column 8. Region has exactly one open cell left.
  9. Next, place a marker at row 8, column 6. Region has exactly one open cell left. Placing here clears the rest of row 8, column 6, and its region.
  10. Finally, place a marker at row 6, column 1. Region has exactly one open cell left.

The key move here was Region confinement — once you can spot that, this board falls quickly.