Bookcase is an intermediate track. It takes place in a library. There is a cube of aerogel on top of the second green book. The bloons start from the top left corner, and go around and under the books and split and go above and below the aerogel cube. Then they go under an orange book and go around some more books and then leave under a yellow book. Due to books being a symbol of knowledge, your towers can pop anything here, and the Shield Generator can protect double the towers!