Splitting a boulder - GIF

Splitting a boulder. Or, when you tell two kids: "one of you splits the candy bar in half, and the other one chooses which half he wants".

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Previously:

https://www.homemadetools.net/forum/...2114#post75761
https://www.homemadetools.net/forum/...1250#post74040
https://www.homemadetools.net/forum/...2360#post76209
https://www.homemadetools.net/forum/...3037#post97899
https://www.homemadetools.net/forum/...3602#post99570