I finally completed the fourth wall of the treehouse, and lugged it down to the back yard. I adjusted the swing so that it was a bit lower and more user-friendly to its intended audience.

I stood up a couple of the walls and began bolting them together. When they were standing and bolted, I went around and put some more screws in the plywood to hold it on as securely as possible.

With a little bit of help from my father who was visiting, I got all four pieces assembled and bolted together to make sure they fit as intended. It all seemed to go very well, and everything matched up.
Then, the Inspector showed up, with his camera...

but it was all good.
Now that I have the walls assembled on the ground,
I am thinking that since it is so heavy, more supports on the platform will be needed, so that's the next step. More to follow.