QED Logic quod erat demonstrandum

A Steady 7×7 Puzzle Solved with Shape Squeeze in 23 Steps

7×7 · steady · 16 steps

Play this board yourself →
A
B
C
D
E
F
G
1
2
3
4
5
6
7
1×
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×
2×
3🐱
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×
🐱
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4×
🐱
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5🐱
×
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6×
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🐱
7×
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×
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This 7×7 board rates as steady (difficulty score 833). Solving it from scratch takes 23 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 row 7, so its marker has to land there; that clears every other open cell in the row.
  2. Next, 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.
  3. Then, 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.
  4. After that, every remaining candidate in this region touches F2, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
  5. Now, every remaining candidate in this region touches D4 and E4 and E6, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
  6. From there, place a marker at G6. Region has exactly one open cell left. Placing here clears the rest of row 6, column G, and its region.
  7. Following that, every open cell left in this region sits in column F, so its marker has to land there; that clears every other open cell in the column.
  8. First, every open cell left in this region sits in row 3, so its marker has to land there; that clears every other open cell in the row.
  9. Next, place a marker at F1. Region has exactly one open cell left. Placing here clears the rest of row 1, column F, and its region. Placing here also clears its 1 touching neighbour.
  10. Then, every open cell in column C 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.
  11. After that, every remaining candidate in this region touches D3, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
  12. Now, 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.
  13. From there, place a marker at D5. Region has exactly one open cell left. Placing here also clears its 1 touching neighbour.
  14. Following that, place a marker at C2. Region has exactly one open cell left. Placing here clears the rest of row 2, column C, and its region.
  15. First, 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.
  16. Finally, place a marker at B7. Region has exactly one open cell left.

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