The day after... Christmas?
That's what it felt like, anyway, when I spent at least five hours working on this:

D. does the 100-piece ones by himself, but this has 550, and two-thirds of it is really pretty hard. It glows in the dark, too.

D. does the 100-piece ones by himself, but this has 550, and two-thirds of it is really pretty hard. It glows in the dark, too.