this design is brilliant:
I’m going to have to build one for Stella. The best thing is that you can stack books on the other side and see-saw alone. How awesome is that? Also I suppose it can become a game as you try to balance it out into a flat bookshelf while trying to load the exact same weight of books on both sides. Not to mention that jumping on one side can catapult all of your books across the room. Fantastic!