QED Logic quod erat demonstrandum

An Easy 8×8 Logic Puzzle, Solved in 8 Steps

8×8 · easy · 8 steps

Play this board yourself →
A
B
C
D
E
F
G
H
1
2
3
4
5
6
7
8
1×
×
×
2
×
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3×
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4×
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×
×
×
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5×
×
×
×
×
×
×
×
×
×
6×
×
×
×
×
×
×
×
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7
×
×
×
×
×
×
×
×
×
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8
×
×
×

This 8×8 board rates as easy (difficulty score 319). Solving it from scratch takes 8 logical steps, using 3 techniques: Single cell, Row/column exclusion, Adjacency clear. Every step below is forced: nothing here is a guess.

  1. First, place a marker at E8. Region has exactly one open cell left. Placing here clears the rest of row 8, column E, and its region. Placing here also clears its 2 touching neighbours.
  2. Next, place a marker at B7. Region has exactly one open cell left. Placing here clears the rest of row 7, column B, and its region. Placing here also clears its 2 touching neighbours.
  3. Then, place a marker at F5. Region has exactly one open cell left. Placing here clears the rest of row 5, column F, and its region. Placing here also clears its 2 touching neighbours.
  4. After that, 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. Placing here also clears its 1 touching neighbour.
  5. Now, place a marker at A2. Region has exactly one open cell left. Placing here clears the rest of row 2, column A, and its region.
  6. From there, place a marker at H6. Region has exactly one open cell left. Placing here clears the rest of row 6, column H, and its region.
  7. Following that, place a marker at G3. Region has exactly one open cell left. Placing here clears the rest of row 3, column G, and its region.
  8. Finally, place a marker at C4. Region has exactly one open cell left.

This was an easy solve: every step followed directly from placing a marker and clearing its row, column and region. ∎