QED Logic quod erat demonstrandum

An Easy 8×8 Puzzle Solved with Shape Squeeze in 12 Steps

8×8 · easy · 12 steps

Play this board yourself →
A
B
C
D
E
F
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H
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This 8×8 board rates as easy (difficulty score 767). Solving it from scratch takes 12 logical steps, using 5 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement, Shape squeeze. Every step below is forced: nothing here is a guess.

  1. 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.
  2. Next, place a marker at H2. Region has exactly one open cell left. Placing here clears the rest of row 2, column H, and its region. Placing here also clears its 1 touching neighbour.
  3. Then, 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. Placing here also clears its 2 touching neighbours.
  4. After that, 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.
  5. Now, place a marker at C5. Region has exactly one open cell left. Placing here clears the rest of row 5, column C, and its region. Placing here also clears its 2 touching neighbours.
  6. From there, 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.
  7. Following that, every open cell left in this region sits in column B, so its marker has to land there; that clears every other open cell in the column.
  8. First, place a marker at D1. Region has exactly one open cell left. Placing here clears the rest of row 1, column D, and its region.
  9. Next, every remaining candidate in this region touches B7, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
  10. Then, place a marker at B8. Region has exactly one open cell left. Placing here clears the rest of row 8, column B, and its region. Placing here also clears its 1 touching neighbour.
  11. After that, place a marker at A6. Region has exactly one open cell left. Placing here clears the rest of row 6, column A, and its region.
  12. Finally, place a marker at F7. Region has exactly one open cell left.

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