Nice, clear focus, and interesting idea! The composition is a bit cluttered... although it would have been hard to get any good composition in a playground like that with all the crowded lines and angles. Neat shot though! :)
Directly related to the challenge, but it doesn't really reach me as an image. The lighting is harsh, and the colors overpowered by the light at times. I like many of the elements of the composition, with the vertical lines of the railings all running parallel, and sort of driving the eye up toward the tower in the middle, but with this cut off, even that is hard for me to get to grips with. Suits the challenge, but I think there's room here to bring it together as an image, too.
It's called peek-a-boo, but she's not peeking at us at all. The bright sunshine is washing out all the colours too. Overcast weather or sunset can often be much better for photos like this, as the lighting is much less harsh.