When it opened up the entire left-half of my screen is blank, and the diagrams are obviously cut off on the right. There is no apparent way to scroll horizontally (excepting a mouse with a horizontal scroll mechanism of some sort): There is no horizontal scroll bar and neither the arrow-keys nor click-and-drag serve to scroll horizontally. Zooming out made things a bit clear what was going on, (margin notes shifted the content far to the right).

Firefox, 1920x1200 screen.

I don't understand what the point is over just using git. The top intro defined some JJ names for git things, but it's not clear why I would want or need this. What problem does it solve with using git?