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SOLO-038 · Nim — pair subtraction

EXPERT

The Broken Balance

Find all the first shots that guarantee victory, and demonstrate strategy against any adverse response.

Materials: Pencil and paper; optional chips, all pile numbers are given.

Rules you need

The puzzle

You play first. To analyze alone, calculate the winning and losing positions of both sides.

Gives a complete list of the winners and a general proof of answer: only one cooperative suite is not enough.

Coordinates: lines from top to bottom, columns from left to right.
L / C123
1PairPile APile B
21129
32713
Why this level?

Combine mex recurrence and XOR sum of non-standard games; demonstrate a valid strategy for all responses. Sizes do not treat like those of the ordinary Nim. Editorial evaluation based on the required techniques; not calibrated by a human panel.

Your workspace

Write down your assumptions separately from deductions you have proved.