One of the coolest game jam games I've seen! I'd love to learn how you did the 2D projected onto a storybook technique. Super charming art style, and the difficulty was just right for me. My fingers hurt from mashing the J key lol.
The book used two SubViewport nodes, one for the static part of the book and the other for the animated page. It was just a matter of setting up the book's UVs to display one of the two viewports at specific parts of the scene transitions.