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Author/Opus: This is the 1st puzzle from guest contributor Matej Uher.
Rules: Place either an ‘X’ or an ‘O’ into each empty cell so that four consecutive ‘X’s or ‘O’s do not appear horizontally, vertically, or diagonally.
Difficulty: 2 stars
Time Standards (highlight to view): Grandmaster = 2:00, Master = 2:45, Expert = 5:30
Note: Follow this link for other Number Placement puzzles.