Text version of this lesson
A single sentence can describe a whole board. Build the board it describes.
Key takeaway: A rule that mentions a cell's position describes every cell at once — apply it cell by cell and the pattern appears.
Question 1
Light the grid that follows the rule.
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Why: That is the main diagonal: position matched to position.
Hint: Go row by row and ask which column number matches the row letter.
Question 2
Light the grid that follows the rule.
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Why: Every row holds two lights: shifting moves a pattern but never changes how much of it there is.
Hint: Shift row A right by one: the light in column 3 wraps around to column 1.
Question 3
Light the grid that follows the rule.
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Why: A count says how many, a placement rule says where. You need both to pin one grid.
Hint: Each row starts at column 1 and fills right.
Question 4
Which lights are ON?
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Why: That is the chessboard pattern: four corners plus the centre.
Hint: Five is the most you can fit on a three-by-three board without touching.
Question 5
Light the grid that follows the rule.
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Why: "Both" narrows twice: first the rows, then the columns. Four lights survive.
Hint: Only rows B and D qualify, because only 2 and 4 are even.
Question 6
Light the grid that follows the rule.
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Why: The middle column is its own mirror image, which is why it stays lit in both rows.
Hint: Mirroring swaps column 1 with column 3 and leaves column 2 where it is.