Griddlers Tutorial - Solving Puzzles
More Color Logic
Here are three more examples that illustrate color logic.
Here we have two "O"s separated with two empty squares. At most, a block of 2 reds can go between them. But both red clues are over two (in this case both are three).
Therefore we can fill the empty squares in between the 2 "O"s.
In this case we have two black squares filled in. They are separated by two empty squares. These empty squares can't be filled with red since the red clues both have more than 2 squares. They also can't be filled in with a white (background) square since that would give us two black clues side by side in the set of row clues (which we don't have).
Here's what the puzzle would look like if the square is the beginning of clue 7.
Here we have a block of two black. We have put "O"s at the beginning and end of the line. Can we do anything else here?
Case 1: The existing block is the first clue
If the block is the first clue then everything before it is white (our background color).
Case 2: The existing block is the last clue (black3)
If the block is part of the last clue then we know that it MUST be preceded by at least one white square and one black square before any red squares are filled in.
In any case, we can fill in two more "O"s before this block of two blacks indicating that these squares can only be black or background. The result would be: