LG-008

Constraint puzzle: A code uses 3 colors. You know:
1) purple is used.
2) If blue is used, then green is not used.
3) red is not used.
Which set of colors is possible?

We must include purple and exclude red.

If we include blue, we must exclude green.

The only option that satisfies all constraints is: purple, blue, yellow.

• Picking the first pattern you see without checking it against all rows/columns.
• Ignoring the simplest rule (counts, rotations, alternations) and jumping to a complex story.
• Not testing your rule on the middle row/column (where many puzzles “break” bad rules).