Testing hypothesis: For every constraint, there is an equal and opposite anti-constraint. Research into quadruples has turned up anti-quadruples in far greater quantities than theory suggested. Further research will be required.
Rules:
Normal Sudoku rules apply.
Digits within uncolored circles appear at least once in cells touching the circle.
Digits within colored circles do not appear in cells touching the circle.
Estimated difficulty: 1.5 out of 5
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