Stairway to Heaven

Last night I stopped and it was pretty clear they made headway.  All the joists for the 2nd floor was installed, the plywood floor was laid.  They also installed the stairway.  I was able to go to the 2nd floor and walk around.  The plywood floor while it is particle board is glued down and nailed in place.  I had friends complained about some floors not feeling solid or making sound, but ours seemed not to have any give or made any sound.

Some observations:
1) Our kitchen has another framed wall nailed to the actual wall.   It seemed odd as this wall doesn't go to the ceiling joists.  I suspect this is maybe for the kitchen cabinets, but again kind of weird.
2)There is a 1/4 inch gap in the wall between the powder room and the study.

Hopefully when I go this evening they will have the 2nd floor walls up and maybe some windows.

Now for a few pictures.

The large gap in our external wall

The inside gap in our walls showing light coming in