I like the construction animation (also the parts where the bricks seem to have their own will), but I would have liked it if a once constructed wall were to stay instead of being demolished and rebuild over and over again. That way one has a less busy picture to compare with what you say. Maybe instead at the end of the chapter demolish the wall once? Anyways, thanks for showing and explaining so many variaties, I would not have expected there to be so many!