That is awesome! Can I ask how sturdy it is? I really want to build something like that but I have some rough and tumble kids. I had a kid-sized tent, but it lasted less than a week due to kids (well, one in particular) jumping on it.
A friend told me about a fort she built out of milk cartons and I was planning on doing that, but it will take me years to save the cartons, especially since I buy milk in plastic jugs! Cereal boxes seem much more feasible!