Seems to be nothing more than an ad for a book? Also, these things are usually called “Space-filling curves” (<a href="https://en.wikipedia.org/wiki/Space-filling_curve" rel="nofollow">https://en.wikipedia.org/wiki/Space-filling_curve</a>).<p>EDIT: I missed the “Read Online” link - it is indeed a whole book about space-filling curves with lots of pictures.