If you look at the linked submission you'll see that the DataGenetics blog post is referenced. Personally, I found that to be too detailed in some parts, and not detailed enough in others - I felt it got the balance wrong. Of course, everyone's mileage will vary, but this intended audience for the item will tend to be more interested in the "NIM sum" than the XOR, even though they are the same thing. The "NIM sum" is what's used in mathematical games and puzzles, and will be familiar to the intended audience.

But again, YMMV, so you may prefer the DataGenetics version.