The description, which says that you can start at any of the first 12 words, doesn't seem quite right; you can start on any of the first 8 words and it works, which seems amazing (but apparently isn't—I haven't read the linked analysis), but starting at the 9th ('sitting') or the 11th ('her') will leap-frog you right over 'sister'. (I suppose it's debateable whether or not this 'works' starting at the 12th word, depending on whether you count starting there as winding up there.)
Obligatory XKCD: <a href="https://xkcd.com/903/" rel="nofollow">https://xkcd.com/903/</a><p>Ah, but unlike any other obligatory XKCD you tend to see on HN, the relevance here isn't in the comic but in the alt-text you get when you hover over the image.