Bonus

The book is done. You have built the tower three times over, for one machine, for one hostile box, and for many machines, and you have traced a message through all of it.

What follows is a bonus, and it is placed last on purpose. It adds no rung. It takes the tower you already have and puts it under a third kind of load, unlike either of the two that ran through the book, and the point of it is the contrast. It can only be read well by someone who has chat and video to compare it against, so keep both in mind as you go. The tower will turn out to be the same tower. What matters on it will not.