Since it was once his childhood dream to have an indoor treehouse, this guy decided to make the dream a reality for his 5-year-old son. He gathered a bunch of wood and then got to work, sharing pictures of the process on Reddit with the very appropriate username d4ddycool.
Here are some shots of the early stages and then, finally, the finished product:
He explained that he built in some storage space but, ultimately, was "building stuff with no real plans in mind." Because none of his house's walls are perfectly straight, he struggled with alignment and went through a good amount of trial and error. From the looks of it, it turned out pretty well.