The Sonic Hedgehog Girl's Cave-Treehouse

Entrance is a pile of rocks in the forest; behind them is a loopy-loop slide leading down into a giant underground cave. Inside the cave she built a treehouse — “half the tree is house and half the tree is tree,” approximately two-thirds house. Has running water, electricity, and a generator. She dug a hole through rock to let light in for the tree to grow. Ten floors, each connected by a loop-de-loop slide down to a ball pit; ascending uses a pneumatic air-blast tube with balls inside. The cave yard has a slime pool (non-sticky, temperature-controlled), a hot tub, and a self-cleaning “cool pool.” She is constantly building and adding onto it.