this picture has the subject to the left of the frame, and she is surrounded by the bars on both sides of her, and the treehouse floor above her. the tree to the right of her also helps focus your attention to her.
the steps of the ladder as well as the siding of the ladder help to narrow down the focus to just where she is standing. there isn't much else to focus on, just the girl surrounded by the steps.
this frames the girl to the left of center, and has the wood pieces below and to the right of her. The tree in the background also helps direct your attention to her.
with the subject off center to the left and the tree house surrounding her, your eye focuses to the middle piece of wood, and then to Devin sitting off to the side, framing her within a frame.
with the fence out of focus, your eye narrows to between the two pieces, to the girl laughing off center to the left.
the center of this frame would be the middle of the tree, but since there isnt much to focus in on, it directs your attention to both faces, the one on the bottom left and the one on the top right.
the center of this picture is the house in the background, which is out of focus to direct your attention to the girls sitting side by side, on opposite sides of the frame.
the bar in the middle and the girl out of focus in the background directs your attention to both girls standing looking at each other.
with her arms being the middle of the frame, your eye follows them to the girl to the right, who is swinging on a tree.