Something to stand upon

When building the deck, I was basically balancing on top of the platform joists. Once the deck and railing were finished, it was time to get to the floor (subfloor actually). I mostly used exterior grade ¾” plywood for this, patching together the U-shaped footprint for the treehouse. I tried to span multiple joists if possible for more stability. In the photo, you can readily see the hole for the trapdoor :)